Dalbränd Tjära På Stavkyrkor Och Andra Hustyper Samt Båtar

DALBRÄND TJÄRA PÅ STAVKYRKOR OCH ANDRA HUSTYPER SAMT BÅTAR

Sammanfattning av seminarium

Nordic Tar network 8-10 okt 2018 Oslo & Tønsberg, Norge

1 INNEHÅLLSFÖRTECKNING Nordic Tar network ...... 3 Nätverkets fjärde seminarium ...... Fel! Bokmärket är inte definierat. Seminarieprogrammet i korthet ...... 3 Besök på Vikingskipshuset, Historisk museum, Oslo ...... 4 Förindustriell tjärkunskap – några reflektioner, Inger Marie Egenberg ...... 4 Rundvisning i och runt stavkyrkan med information om deras tjärbränning ...... 5 Gildehallen, Midgard vikingacenter ...... 6 A Chemical Approach to Analytical Tar Identification, Kiat Bergen ...... 6 Tjära på Gotland - Nya försök med gamla metoder. Frode Falkenhaug, Pär Malmros ...... 6 Tilgang på og bruk av milebrent tjære til stavkirker, Merete Winness ...... 7 Hva er forskjellen på milebrent og ovns brent/retorte brent tjære? Ole Jørgen Schreiner ...... 7 Nyheter från Finland ...... 8 Samtal om en kommande publikation och nätverkets framtid ...... 9 Tjära - Vikingatidens svarta guld. Andreas Hennius ...... 10 Fler länkar ...... 11 Bilder ...... 12 BILAGA ...... 12

2 Nordic Tar network Den 8-10 oktober 2018 anordnades den fjärde träffen inom ramen för det nordiska nätverksprojketet om tjära, Nordic Tar network, i Oslo och Tønsberg, Norge. Nätverket, som startade 2017, har fått ett treårigt nätverksbidrag från Nordic Culture Point för att anordna träffar i Sverige, Norge och Finland. Den första träffen i nätverket ägde rum 29-30 maj 2017 på Gotland, Sverige, och hade temat Bränning av tjära på Gotland. Träff nummer två arrangerades 23-24 oktober 2017 i Saarijärvi, Finland. Tredje träffen blev åter i Finland 4-5 juni 2018 på Fölisö friluftsmuseum, Helsingfors, Finland, och ägnades åt tjärsevärdheter i Nyland samt tjärning on-site. Under 2019, planeras ytterligare två träffar, en i Norge och en i Sverige. Det nordiska nätverket om tjära har till syfte att skapa möten mellan hantverkare, producenter, återförsäljare, kulturmiljövårdens organisationer, fastighetsägare, fastighetsförvaltare, utbildningsinstanser och föreningar i Norge, Sverige och Finland. De olika intressenterna besitter en mångfald av kunskaper och erfarenheter vad gäller exempelvis tjärkvaliteter samt hantverksprocesser förknippade med tjärframställning och tjärstrykning. För att komma vidare i kunskapsuppbyggnaden är det av betydelse att identifiera, kartlägga och dokumentera befintlig kunskap i de olika yrkesgrupperna och länderna. Under de träffar som arrangeras inom projektet besöks produktionsanläggningar och intressanta restaureringsobjekt där tjärningsarbeten planeras, pågår eller har genomförts. Målet är att vid projektets slut dels ha dokumenterat den kunskap som framkommit, dels ha etablerat en plattform som gör det möjligt att söka fortsatt stöd från internationella fonder för vidare kunskapsuppbyggnad.

Nätverkets fjärde seminarium Seminariet i Norge arrangerades i samarbete med Norsk folkemuseum, Oseberg vikingaarv och Fortidsminneforeningen (för program och deltagarförteckning, se bilaga 1 och 2). Bakgrunden till samarrangemanget är att det inom dessa organisationer finns omfattande kunskap om och erfarenhet av att vårda tjärstrukna båtar och byggnader, samt av dokumentation och forskning i anslutning till detta. I Kulturhistorisk museums samlingar finns flera vikingatida skepp, däribland Osebergsskeppet som i restaurerat skick till 90 procent består av originalmaterial. En kopia av detta skepp, under namn Saga Oseberg, seglar idag på Tønsbergfjorden. De många norska medeltida stavkyrkorna är naturligtvis också av stort intresse när tillverkning och användning av tjära diskuteras.

Seminarieprogrammet i korthet Seminariet inleddes måndagen den 8 oktober på Norsk folkemuseum i Oslo. Efter lunch på museets restaurang Kafé Arkadia besöktes Vikingskipshuset, som är en del av Kulturhistorisk museum vid Oslo universitet. Där fick deltagarna se utställningen med de tre vikingatida skepp som bevarats i Norge. Bjarte Aarseth, överingenjör och träsnidare vid museet, berättade om det pågående arbetet med att 3D-scanna fynd från Osebergsskeppet, något som gör det möjligt att både utveckla kunskap kring hur fynden fortsatt bäst kan konserveras och att tillverka exakta kopior av dessa. Därefter föreläste Inger Marie Egenberg, fil dr i konservering och chef för avdelningen för konservering, Arkeologisk museum vid Universitetet i Stavanger, på temat Förindustriell tjärkunskap – några reflektioner. Efteråt vandrade deltagarna upp till den stavkyrka som ingår i friluftsmuseet på Norsk folkemuseum. Kyrkan stod öppen och på planen utanför berättade Ole Jørgen Schreiner, hantverkare vid Norsk folkemuseum, om den tjärberedning som är en förutsättning för att väggar och tak kontinuerligt ska kunna tjärstrykas. Mogens With, arkitekt och byggnadsantikvarie vid Norsk Folkemuseum, berättade kort om stavkyrkans historia.

3 Mot slutet av dagen gick färden vidare till Tønsberg. En vikingatida middag åts i Gildehallen på vikingacentret Midgard i Borre med Vestfold fylkeskommune som värd. Tisdagens förmiddag ägnades åt föreläsningar och samtal på Slottsfjellmuseet i Tønsberg på temat kvalitet respektive tillgång på tjära. Kiat Bergen, konservator, föreläste med utgångspunkt i sin masteruppsats A chemical approach to analytical tar identification. Frode Falkenhaug, Gotlands museum, och Pär Malmros, Visby stift, rapporterade från projektet Tjära på Gotland – Nya försök med gamla metoder. Merete Winness, Fortidsminneforeningen, berättade om Tilgang på og bruk av milebrent tjære til stavkirker, Ole Jørgen Schreiner, Norsk folkemuseum, om Hva er forskjellen på milebrent og ovnsbrent/retortebrent tjære? Därefter ledde Antti Pihkala, Evangeliska lutherska kyrkan i Finland, ett samtal om en eventuell publikation inom det nordiska tjärnätverket respektive en möjlig fortsättning i form av ett nytt projekt. Andreas Hennius, doktorand vid institutionen för arkeologi och antik historia vid Uppsala universitet, avslutade förmiddagen med att föreläsa om Tjära - Vikingatidens svarta guld. Den båttur med Saga Oseberg som var tänkt att äga rum på eftermiddagen fick tyvärr ställas in på grund av stark blåst. Deltagarna fick dock en intressant guidning ombord under medverkan av två av de ideellt arbetande eldsjälar som varit med under skeppets tillkomst och nu är med och förvaltar det. Kvällens middag intogs på Villa Møllebakken, där bland annat en kopia av en vagn från Osebergsskeppet med omfattande träsniderier väckte stort intresse. På onsdagen åkte seminariedeltagarna till Høyjords stavkyrka för visning och fortsatt diskussion om tillverkning och användning av tjära. Efter lunch på plats avslutades det tre dagar långa seminariet.

En kort redogörelse för seminariets olika programpunkter följer nedan.

Besök på Vikingskipshuset, Historisk museum, Oslo Historisk museum har i sina samlingar tre vikingatida skepp. Det mest välbevarade är Osebergskeppet, som 1903 återfanns i en gravhög på gården Oseberg i trakten av Tønsberg. I skeppet, som senare kunnat dateras till 820-talet, fann arkeologerna bland annat en omfattande samling lämningar efter vikingatida träföremål. Sammantaget utgör Osebergsfynden ett av de viktigaste arkeologiska fynden i Norge, som också fått status som nationalklenod. Träföremålen är dock i dålig kondition på grund av de konserveringsmetoder som användes vid 1900-talets början. Efter utgrävningen 1905 konserverades de mest medfarna föremålen med alunsalter, vilket då var den bästa metod man kände till. Det har dock visat sig att denna behandling långsamt bryter ner materialet.

På Vikingskipshuset pågår sedan ett antal år ett arbete med att dokumentera Osebergsfynden med hjälp av 3D-scanning. Bjarne Aarseth, som är ansvarig för arbetet, visade hur det med hjälp av en portabel utrustning går att rita upp koordinater med extrem precision. 3D-scanningen innebär att fynden säkras digitalt. Informationen kan sedan användas för att tillverka exakta kopior av olika föremål, vilket deltagarna fick se exempel på. Genom 3D-scanning kan forskare dessutom följa nedbrytningsprocessen över tid, vilket dels gör det lättare att ta hand om fynden på ett bra sätt, exempelvis genom tillverkning av bättre stöttor till skeppet, dels möjliggör utveckling av nya konserveringsmetoder. Projektet finansieras av norska staten och Universitetet i Oslo. Läs mer om arbetet här: https://www.khm.uio.no/forskning/prosjekter/saving-oseberg/

Förindustriell tjärkunskap – några reflektioner, Inger Marie Egenberg Inger Marie Egenberg, fil dr i konservering och chef för avdelningen för konservering, Arkeologisk museum vid Universitetet i Stavanger, föreläste på temat Förindustriell tjärkunskap – några reflektioner. Till grund för föreläsningen låg erfarenheter ur det så kallade Tjæreprosjektet som pågått sedan 1991. De senaste 20 åren har Riksantikvarien i Norge föreskrivit att de medeltida stavkyrkor som fortfarande behandlas med tjära ska strykas med milbränd sådan. Begreppet tjära

4 används i Norge , liksom i Sverige och Finland, närmast synonymt med det mer precisa begreppet tyritjaere. Tyri står för den hartsartade kärnved av furu som utgör råvara för tillverkningen av denna tjärtyp. Traditionellt har tillverkningen skett genom milbränning. Tekniskt sett handlar det om torrdestillation även om hartserna som utgör tjärans huvudsakliga beståndsdel smälter och rinner ut ur veden. Del 1 av projektet har handlat om att undersöka serier av prover från olika tjärbränningar ur såväl kemisk som fysikalisk synvinkel. Frågor som ställts är hur kvaliteten på de olika proverna kan beskrivas, om och i så fall hur den varierar samt vilka skillnader som finns mellan milbränd och fabrikstillverkad tjära. Del 2 av projektet har handlat om praktiska strykningsförsök i naturligt utomhusklimat. Ett antal tjärkvaliteter har under tre år utsatts för väder, vind och olika väderstreck för att se hur de reagerar och förändras över tid. Huvudkomponenter i tyritjaere är abietinsyra och dehydroabietinsyra. Den förstnämnda dominerar i furuhartser och därmed också i den tjära som produceras i början av en bränning. I takt med att temperaturen under bränningen ökar ersätts den som huvudsaklig beståndsdel av dehydroabietinsyra. I Norge finns sedan 1980-talet en tjärbank som fungerar så att tjärbrännarna sänder prover och ett schema som beskriver bränningen till Riksantikvarien som godkänner tjäran. Den köps sedan in av Fortidsminneforeningen som säljer den vidare för användning i stavkyrkorna. Normen för godkänd tjära är i detta sammanhang: Specifik vikt: 1.03-1.07 g/ml Andel av flyktiga beståndsdelar: 8-18 % Andel av vattenlösliga beståndsdelar: 2-6 % Viskositet (ett mått på ”tjockhet” eller friktion i vätskor): 990-9160 mm 2/s Fysikaliskt ska tjära för att hålla hög kvalitet vara homogen och fri från vatten. En kornig konsistens är inget problem bara det handlar om den slags kornighet som försvinner vid lätt uppvärmning. I annat fall ska den vara transparent och gyllenbrun vid strykning. Det som kännetecknar milbränd tjära är inte att den nödvändigtvis är bättre än industritillverkad tjära, utan att den omfattar en stor variation vad gäller homogenitet, viskositet etc och därför måste användas på ett sätt som tar hänsyn till de särskilda egenskaperna hos varje fraktion. Den bristfälliga tillgången på tjära för kulturvårdande ändamål är ett problem. Inger Marie Egerberg listade några viktiga åtgärder för att öka densamma: Tätare kontakter med nuvarande producenter, nyrekrytering av producenter, i olika sammanhang uppmärksamma behovet av mer tjära, uppmärksamma skogsnäringen m fl på behovet av mer råvara av rätt kvalitet. Mer forskning vad gäller tjära behövs, menade Egerberg. En fråga är var den brukats historiskt – går den att finna i arkeologiskt provmaterial? En annan fråga är om/hur en framtidsinriktad produktionsutveckling av god milbränd tjära för användning i kulturmiljövården kan kombineras med en bärkraftig produktion. Läs Inger Marie Egerbergs artikel Milebrent tyritjære: Tekniske egenskaper og et historisk korrekt vedlikehold här: http://www.academia.edu/1470486/Milebrent_tyritjære._Tekniske_egenskaper_og_et_his torisk_korrekt_vedlikehold

Rundvisning i och runt stavkyrkan med information om deras tjärbränning Det friluftsmuseum som idag är en del av Norsk folkemuseum började byggas 1881. Oscar II, då kung över den svensk-norska unionen, lät flytta fem äldre byggnader till området. Samlingen av byggnader skulle representera ett äldre säreget byggnadsskick och samtidigt understryka kungens intresse för Norge. En av dessa byggnader var stavkyrkan, ursprungligen uppförd i Gol, Hallingdal, på 1200-talet och flyttad till Oslo 1884. Bara en tredjedel av materialet ansågs dock vara från medeltiden. Resten av stavkyrkan rekonstruerades med Borgund stavkyrka som förebild. År 2001 startade den norska riksantikvarien ett program för att sätta i stånd alla landets stavkyrkor. 2001 var det Norsk Folkemuseums tur. Det byggdes ställningar kring hela kyrkan och allt takspån byttes ut. Nya brandvarnare monterades och merparten av drakornamentiken och nockdekorationerna förnyades. Inget av detta var original, utan

5 hade tillkommit när museet uppfördes eller senare. Tidigare hade man haft stora problem med att få tjäran att fästa. En anledning var förmodligen att de gamla spånorna var av dålig kvalitet och att många olika tjärprodukter tidigare hade använts, exempelvis stenkolstjära som inte fungerar bra ihop med trätjära. De nya takspånen består av kärnved med stående årsringar, och man har varit noga med att följa upp tjärstrykningen i efterhand. Man försöker att göra en del varje år och har erfarenhet av att utföra tjärstrykning på hösten, efter lövfall och före snöfall. Då står solen inte så högt och det blir inte så mycket avrinning. Men vädret kan vara en utmaning. Det bör vara torrt vid påstrykningen, men erfarenheter från Norsk Folkemuseum visar att stora nederbördsmängder efter tjärstrykningen ändå inte påverkat resultatet negativt. Erfarenheter finns också av att inkokt tjära klarar sig bättre, men skillnaden bedöms inte vara så stor att det är värt merarbetet. Här kan lagring av tjäran vara en möjlighet, dock har inga försök gjorts vad gäller det. https://norskfolkemuseum.no/stavkirke

Gildehallen, Midgard vikingacenter Midgard vikingsenter har till uppgift att förmedla kunskap om Vestfolds vikingatid. Centret ligger i anslutning till Nordeuropas största samling av monumentala gravhögar från den tiden. 2007 återfanns spår av stora hallbyggnader i området, varav en har rekonstruerats. Gildehallen, som alltså är en rekonstyruktion av en av vikingatidens stora festsalar, togs i bruk 2013. Seminariedeltagarna fick avnjuta en vikingatida middag, serverad av personal med vikingatida kläder, med sång och deklamation. Läs mer om Midgard vikingsenter: https://midgardvikingsenter.no/om-midgard/velkommen-til-midgard-vikingenes-verden/

A Chemical Approach to Analytical Tar Identification, Kiat Bergen Kiat Bergen medverkade under den första tjärträffen på Gotland i juni 2017. Hon var då mitt uppe i arbetet med sin masteruppsats i konservering. Denna gång kunde hon presentera resultatet som är en jämförande studie av metoder för att analysera tjärans kemiska sammansättning. En underliggande fråga är om det går att hitta en industriellt tillverkad tjära med liknande kemiska egenskaper som den industriellt producerade. Tjära framställd på traditionellt sätt anses oftast vara av högre kvalitet, men är det verkligen så? Bergen har undersökt två kemiska analysmetoder I avseende på deras användbarhet för att kemiskt analysera tjära. För att vara användbar måste respektive metod inte bara kunna mäta den kemiska sammansättningen, den måste också vara enkel att använda, gå att utveckla i fält och kunna användas till en låg kostnad. De två metoder som ingick I undersökningen var Thin Layer Chromatography (TLC) och Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR), varav den förstnämnda visade sig ha flest fördelar. Läs mer i Kiat Bergens uppsats A Chemical Approach to Analytical Tar Identification: An Exploration of the Chemical Composition of Industrial and Traditional Produced Tars som bifogas denna rapport (bilaga 3).

Tjära på Gotland - Nya försök med gamla metoder. Frode Falkenhaug, Pär Malmros Frode Falkenhaug, Gotlands museum, och Pär Malmros, Visby stift, rapporterade från projektet Tjära på Gotland, som nu är inne i delprojekt 2. Det första projektet pågick under 2017 och handlade mycket att söka ny kunskap om gotländsk tjärtradition, dels genom arkivsökningar, dels genom fältundersökningar av tjärprover. Möten med såidesbrännandde hembygdsföreningar arrangerades i samarbete med Gotlands hembygdsförbund. Östergarns-Gaammelgarns hembygdsförening medverkade till att en temperaturmätning i såide kunde genomföras. Det andra projektet inleddes 1 maj 2018 och pågår året ut. Det sker i samarbete med Visby stift, egendomsnämnden och samfälligheten Gotlands kyrkor. Syftet är att öka kvaliteten på den gotländska tjäran genom förbättring av metoder för bränning och applicering. Delmål:

6 • Utveckla appliceringsmetoder tillsammans med tjärsmörjare • Hitta metoder för bättre råvaruförsörjningen till tjärbränning. • Undersöka retort (ugnsbränning) som industriell teknik för framställning av lågbränd tjära. • Tillgängliggöra kunskaper om tjära genom permanent informationstavla på Kulturreservatet Norrbys. • Fortsätta nätverksarbetet mot såjdeslag, skogsfolk och tjärbrännare samt Nordic tar Network.

Katning /randbarkning (slinnebarking) av skog sker i samarbete med ALMI, Fetvedens vänner och AB Gotländskt Kärnvirke Ta del av några resultat från projekten i bifogad PP-presentation (bilaga 4).

Tilgang på og bruk av milebrent tjære til stavkirker, Merete Winness Merete berättade kortfattat om norskt samarbete kring kunskapsutveckling om kvalitet och användning av milbränd tjära samt för att upprätthålla traditionen och produktionen. Hon underströk hur viktigt det är att dela kunskaper och erfarenheter mellan producenter, användare och förvaltare. Det har betydelse inte bara för att få goda resultat utan också för att föra traditionen med milbränning vidare. Under 1980-talet var traditionen med att producera tjära i milor nästan borta i Norge. På skyddade byggnader, inklusive stavkyrkor, användes stenkolstjära. Sedan dess har medvetenheten om skador, tradition och miljö ökat och olika åtgärder vidtagits. Ett viktigt steg var den godkännandenorm för milbränd tjära som kom 1993, vilken byggde på laboratorietester av provserier av tjära. Ett produktionsschema utarbetades som de producenter som ville sälja tjära till stavkyrkorna fick fylla och skicka in tillsammans med tjärprover. Efter godkännande kunde Fortidsminneforeniungen administrera köp och försäljning. Den norska Riksantikvarien ställer idag krav på att restaurering ska ske med traditionella material och metoder, vilket innebär att stavkyrkorna ska strykas med milbränd tjära. På detta sätt bevaras hantverket och den traditionella materialförståelsen. Av 28 bevarade stavkyrkor tjärstryks idag 23 helt eller delvis. Läs mer i bifogad pdf-fil (bilaga 5).

Hva er forskjellen på milebrent og ovns brent/retorte brent tjære? Ole Jørgen Schreiner Ole Jørgen Schreine spann vidare på några av de frågor Inger Marie Egenberg tog upp i sin föreläsning. Riksantikvariens ambition är att använda det mest autentiska materialet till stavkyrkorna, men vad skiljer de två tillverkningssätten åt? Han tog också upp frågor kring lagring och tillgång på tjära. Ur Ole Jørgens presentation: I en mile tappes tjæren etterhvert i brenningsforløpet og vi vet at egenskapene til tjæren endrer seg utover i produksjonen. I en mile er veden direkte utsatt for varmen og forkulles etterhvert. Tjæren drives innover og kondenserer mot frisk tyri, før den samles i bunnen og tappes. Temperaturen stiger etter hvert i brenningen, noe som påvirker egenskapene til tjæren Slik jeg har forstått tjære ovnen, varmes ovnskammeret opp til omtrent forkullings temperatur som er omkring 270°C, da vil forkullingen også gi egenvarme. Tjæren som produseres blir mer homogen. I tillegg kan en utvinne terpentin og eddiksyre. Men er det andre vesentlige forskjeller? Tjærens beskaffenhet, fraksjon, lagring er noe som kan påvirke egenskapene. Jeg tenker at hver gang vi er oppe å tjærebrer vår kirke, erfarer vi hva som fungerer med den tjæren vi har for hånden, og vår viktigste lærdom er at vedlikehold er viktig, tjære blir en ikke ferdig med en gang for alle. Men så! Hva skal til for at vi fortsatt skal kunne få tak i tjære av en slik kvalitet som vi ønsker oss? Slik jeg oppfatter det kan milebrent tjære sees på som vin. Det vil være små

7 variasjoner fra mile til mile ut fra hvordan og hvor milen er brent, miletype, råvarene osv. så det ideelle ville være å bruke tjære fra en mile. Men det er vanskelig å få til i praksis. Og hvor mye betyr det, denne nyansen mellom miler? Målet er jo å få på et sjikt som står lengst mulig, spesielt på tak, og da er vår erfaring at det må påføres flere strøk de først 2-3 årene, før en kan drive løpende vedlikehold. Vi prøver å være oppe på vår kirke vært år for å tjære de mest utsatte flatene. Hvordan kan vi få til en produksjon av den tjæren vi ønsker oss? Det er ingen lønnsomhet i tjærebrenning lenger, og vi greier ikke å konkurrere på pris med den importerte tjæren. Jeg tror Gotland er et godt eksempel på hvordan det kan gjøres, stimulere lag og foreninger lokalt til å bli interessert, eventuelt gi litt økonomisk støtte, for å kunne stille krav til utførelse, slik at vi får den tjæren vi ønsker. Men det er mange utfordringer. Miljøvern interesser skal også vises hensyn, i forhold til å finne virke og ikke minst med selve brenningen. Grunneiere må være med, jeg ser at tyri er til salgs som peisved og skal en betale den prisen for spik til en mile, blir tjæren dyr. Tilslutt litt om oppbevaring. I dag tappes det meste på stål fat eller plastkanner, men jeg tror tjæren har godt av å utvikle seg på trefat. Det blir sagt at tretønnene lekker, men noe skyldes at det er blitt brukt sildetønner som hele tiden er beregnet til å stå våte og kravet til materialet i tønnestavene er derfor ikke så streng. En tjæretønne må lages av tør og kvistfri material og med kantved, stående årringer. Tjære sørger ikke for trutning på samme måte, så den må være tett i tørr tilstand. Tjæren får puste i en tretønne og blir bedre etter lagring. Minst to år har jeg hørt sagt før den skal brukes. Og tønnen skal ikke fylles helt, den utvider seg i varme og tønnen kan sprenges. Jeg har også lært i disse dagene at tjære reagerer med jern og at det dannes en brennbar gass som kan skape overtrykk i stålfatene. Det jeg håper å få svar på er hvilke krav vi kan stille. Er produksjonsmåte vesentlig? Har emballasjen betydning? Hva med lagring? Hva er bare synsing og hva er etterprøvbart.

Nyheter från Finland Antti Pihkala, överarkitekt inom Evangeliska lutherska kyrkan i Finland, kunde rapportera goda nyheter från Föreningen Leve Tjära (Eleköön Terva Ry) som arbetat för att få till stånd ECHA-registrering av tjära. Denna registrering blev färdig i maj 2018. De finska deltagarorganisationerna är Musieiverket (Elisa Heikkilä, Jani Puhakka), Föreningen Leve Tjära (Ilkka Pollari, Juha Pyötsiä), Ev lutherska kyrkan (Antti Pihkala). ECHA /European Chemicals Agency) är den europeiska myndighet som genomför EU:s kemikalielagstiftning. ECHA-registrering syftar till att säkerställa att kemiska produkter hanteras säkert i hela distributionskedjan. Den kan ske efter det att en dokumentation lämnats in och godkänts. Ur Antti Pihkalas presentation:

8 Ett annat tema som är aktuellt i Finland är utarbetandet av en anvisning för tjärning av spåntak. Antti Pihkala och Jani Puhakka är engagerade i detta. Antti Pihkala nämnde också företaget Hautaterva och deras tillverkning av tjära (AP, CP), samt den ”vanliga” tjärproduktionen som sker i en tjärdal genom Museiverkets försorg.

Samtal om en kommande publikation och nätverkets framtid Antti Pihkala ledde ett samtal om en eventuell publikation inom Tjärnätverket respektive en möjlig fortsättning i form av ett nytt projekt. Han inledde med att konstatera att det visat sig vara en god idé att starta ett nätverk. Satsningen har möjliggjort träffar i de tre länderna och resulterat i ett givande utbyte mellan människor som på olika sätt är engagerade i tillverkning och användning av tjära. Någon form av publikation för att sprida resultaten från projektet är önskvärd, men hur ska en sådan se ut? Röster ur diskussionen: • Vilket språk ska användas? En idé är att varje författare skriver på sitt modersmål och att varje artikel sedan förses med en engelsk sammanfattning. Det är bra att skriva på det egna språket eftersom det är viktigt att också bevara specifika ord och uttryck kopplade till bränning och användning av tjära. Också det är en del av kulturarvet. Skriften bör finnas på engelska – det vore fint att få delge denna kunskap även till länder utom Norden.

• Vilken slags publikation är lämplig? Sammanställningen av kunskap är viktigast. Skriften bör fungera som ett gemensamt uppslagsverk. En annan möjlighet är att ha ett levande dokument som fylls på efter hand. Det behöver inte vara en gigantiskt tjock bok. En sida på nätet som tar upp dessa frågor är viktig. Alla har vi olika frågor. Mycket kunskap finns i gruppen. Vi behöver ett forum för detta. Det är viktigt att tänka långsiktigt – materialet bör publiceras digitalt så det är lätt tillgängligt och finns kvar. En bok kräver mycket arbete. Blir den för akademisk missar vi målet. Då når vi inte ut. En bok blir snabbt inaktuell. Det är viktigt att arbeta med både bok och websida – båda spåren parallellt. Nätverkets teman är produktion, användning, kvalitet. Det bör bara vägledande även i arbetet med en bok. En bok bör vara på max 100 sidor. Tjockare böcker är svåra att nå ut med. Det vore bra om arrangörsgruppen skulle kunna arbeta vidare med dessa frågor.

• Vad ska hända med nätverket efter projekttidens slut? Ska det läggas ner? Ska det ombildas till en förening? Ska fler länder bjudas in, t ex Danmark och Estland? Ansökan om ett nytt projekt? Gärna en ny ansökan. Ju mer vi fått veta desto fler nya frågor väcks. En nya ansökan bör utgå från två frågor: Hur har det gått? Vad återstår att göra? Det är viktigt att framöver också bjuda in till mindre aktiviteter, bränning, tjärstrykning etc.

9 Tjära - Vikingatidens svarta guld. Andreas Hennius Andreas Hennius gav en spännande inblick i vikingatida tillverkning och användning av tjära, och den storskaliga produktion som växte fram: The use of tar and resinous substances dates back far into Scandinavian prehistory. How it was produced, however, was unknown until recent excavations in eastern Sweden revealed funnel-shaped features—now identified as structures for producing tar. A new way of organising tar production appeared in the eighth century AD, leading to large- scale manufacture within outland forests. Intensified Viking Age maritime activities probably increased the demand for tar, which also became an important trade commodity. The transition to intensive tar manufacturing implies new ways of organising production, labour, forest management and transportation, which influenced the structure of Scandinavian society and connected forested outlands with the world economy. Läs vidare här: https://www.researchgate.net/publication/328537590_Viking_Age_tar_production_and_ou tland_exploitation

10 Fler länkar Tjära på trätak Arja Källbom. Gøteborgs universitet, 2015 https://gupea.ub.gu.se/handle/2077/39128

Seminar om tjære, Uppsala, 2016. Lenker til presentasjoner http://craftlab.gu.se/kunskapsbank/seminarier/seminarium-om-tjara

Tjære og tjærebreing Schreiner, Ole Jørgen Norske konserves, nr 2/2012, s.15-20 http://docplayer.me/17508806-Konserves-tjaere-og-tjaerebreing-ole-jorgen-schreiner.html

Seminarium kring tjära och tjärstrykning Riksantikvarieämbetet Visby, 20-21 oktober 2011 http://www.raa.se/publicerat/varia2012_1.pdf

Tjærebreing av stavkirker fra middelalderen Egenberg, I.M. 2000b. (NIKU Fagrapport 12. Oslo: Norsk institutt for kulturminneforskning, NIKU. http://portal-cl1.idium.no/niku.no/filestore/Publikasjoner/NIKUFagrapport12.pdf

Milebrent tjære – kvalitet og slitestyrke Faktaark basert på NIKU fagrapport 012 Tjærebreing av stavkirker fra middelalderen Egenberg, Inger Marie 2001, Norsk institutt for kulturminneforskning (NIKU) http://www.nina.no/archive/nina/PppBasePdf/nnFakta%5C2001_14.pdf

Tjærebreing Riksantikvarens informasjonsark, 2002 http://docplayer.me/24352467-Erfaringer-fra-tjaerebreing-av-stavkirkene-de-senere-ar- tjara-seminarium-21-og-22-januari-2016-uppsala-jan-michael-stornes-niku.html

Milebrent tyritjære, diverse av Inger Marie Egenberg Egenberg, I.M. 2004 Milebrent tyritjære. Tekniske egenskaper og et historisk korrekt vedlikehold (PDF vedlagt) Årbok til Foreningen til norske Fortidsminnemerkers Bevaring 158, 127-136.

Egenberg, I.M. 2003. Tarring maintenance of Norwegian, medieval stave churches. Characterisation of pine tar during kiln-production, experimental coating procedures and weathering. (Göteborg Studies in Conservation / Acta Universitatis Gothoburgensis 12). Göteborg: Göteborg University https://gupea.ub.gu.se/handle/2077/16060

Egenberg, I.M. 2001. Tjære: brenning, koking og bruk. I Strategisk instituttprogram 1996-2001 Konservering: strategi og metodeutvikling, NIKU 104 (ed.) G. Swensen. Oslo: Norsk institutt for kulturminneforskning, NIKU.

11 Bilder

BILAGOR (1) Deltagarlista seminarium (2) Program och inbjudan (3) Kiat Bergens uppsats (4) PP-presentation Tjära på Gotland (5) Pdf: Tilgang på og bruk av milebrent tjære til stavkirker

/Rapport sammanställd av Helena Kåks, Hantverkslaboratoriet

14 NORDIC TAR NETWORK

bjuder in till träff i TØNSBERG – NORGE Dalbränd tjära på stavkyrkor och andra hustyper samt båtar

x?-x? oktober 2018

Bland mycket annat besöker vi Gol stavkirke på Norsk Folkemuseum i Oslo. Därefter fortsätter vi till Tønsberg och Gildehallen på Midgard historisk senter.

Båttur med det rekonstruerade vikingaskeppet Saga Oseberg. PROGRAM xxxdag xx oktober Transport til Oslo Fly til Gardermoen (Oslo) Buss til Norsk folkemuseum Norsk Folkemuseum Lunsj på Norsk Foredrag og se Gol stavkirke, som er en del av museet Transport til Tønsberg Buss til Gildehallen Middag i Gildehallen Foredrag (f.eks. historisk produksjon av tjære) Buss til Tønsberg Overnatting i Tønsberg xxxdag xx oktober Diverse foredrag om tjære Båttur med Saga Oseberg http://sagaoseberg.no Overnatting i Tønsberg? Eller transport til flyplassen

PRAKTISK INFORMATION Norweigan 18.55 och med SAS 20.05 och 21.00. Bussen anländer till centrala Helsingfors omkring 19.00 RESA TILL OCH FRÅN OSLO den 24 oktober. Programmet är anpassat efter flygavgångarna från Helsingford och Stockholm. Gemensam buss avgår BOENDE utanför museet Kiasmas huvudingång vid Manner- Xxxxx, Tønsberg. heimplatsen 2, Helsingfors, måndagen den 23 oktober Se hemsida: http://www.summassaari.fi/en/ kl. 11.00 Inform tion om vart bussen stannar kommer att ANMÄLNINGSLÄNK skickas ut veckan innan seminariet. Via denna länk gör du din anmälan till träffen: Den gemensamma bussen kommer tisdag 24 oktober att lämna av resenärer vid Helsinki-Vantaa flygplats http:.... mellan 17.30-18.00 i tid för flyget till Oslo med Norwei- gan 18.55 från terminal 2. Till Stockholm går flyg med

NORDIC TAR NETWORK Syftet är att i nätverket dela kunskaper och utbyta erfarenheter mellan de nordiska länder- na och mellan olika yrkesgrupper och kompetenser. Under perioden 2017-2019 genomförs sex träffar. Läs mer om nätverket på: www.craftlab.gu.se/natverk/nordic-tar-network NORDIC TAR NETWORK - NÄTVERKSTRÄFF 2018

Dalbränd tjära på stavkyrkor och andra hustyper samt båtar och skepp

Oslo och Tönsberg – Norge 8-10 oktober 2018

PROGRAM

(10.30 Bussen från Gardemoen. Baker Samson (kafé utanför utgången). Kontaktperson Merete Winness telefon 4792247962.)

Mandag 8. oktober 11.30 Ankomst Norsk Folkemuseum. Lunsj Kafe Arkadia 12.30 Besøk i Vikingskipshuset. Om Osebergskipet spesielt. (Bagaget lämnas i ett rum). 14.00 Föredrag: Førindustriell tjærekunnskap – noen refleksjoner - Inger Marie Egenberg, Universitetet i Stavanger 15.00 Omvisning i og rundt stavkirken med informasjon om deras tjærebreing 17.00 Samling Collet gården för avreise med buss til Tønsberg og Gildehallen 18.30 Middag på Midgard i Borre der Vestfold fylkeskommune er vertskap Innsjekking Quality Hotel Tønsberg etter middagen

Tirsdag 9. oktober 09.30 Registrering og kaffe på Slottsfjellsmuseet, Farmannsveien 30.. www.slottsfjellsmuseet.no www.slottsfjel 10.00 TEMA - KVALITET - A chemical approach to Analytical Tar Identification - Konservator Kiat Bergen - Tjära på Gotland - Nya försök med gamla metoder – Frode Falkenhaug, Gotlands museum och Pär Malmros, Visby stift - Samtal om vad vi vet om kvalitet så här långt.

11.00 TEMA - TILLGÅNG PÅ TJÄRA - Tilgang på og bruk av milebrent tjære til stavkirker. Merete Winness - Tilgang og kvalitet. Affärsmodell om produktion av tjära från 1940-talet. Ole Jörgen Schreiner, Norsk folkemuseum - Samtal om småskalig produktion av dalbränd tjära.

NORDIC TAR NETWORK - NÄTVERKSTRÄFF 2018

12.00 Lunsj

13.00 Samtal om idén om en gemensam skrift om Nordic tar network under ledningar av Antti Pihkala, Ev.Luth. Kyrkan i Finland 13.40 Tjära - Vikingatidens svarta guld – Andreas Hennius, doktoran arkeologi, Uppsala universitet 14.30 – 17.00 Pause frem til båttur. Tid til egen disposisjon. 17.00 Båttur med Saga Oseberg. Skeppet ligger vid bryggan invid hotellet.

19.00 Middag på Villa Møllebakken, St. Olavs gate 6. http://www.villamollebakken.no

Onsdag 10. oktober 9.00 Avreise til Høyjord stavkirke. Samtaler om tjærebreing 11.30 Avreise fra Høyjord 13.30 Anländer till Oslo Gardermoen

Husk å ta varme och vindtäta klær til båtturen da det kan være kaldt på vannet på denne årstiden!

Varmt välkomna!

Hälsningar

Merete Winness, Fortidsminneforeningen, 4792247962 Ole Harald Flåten, Saga Oseberg, 4791583585 Ole Jörgen Schreiner, Norsk Folkemuseum, 4740023520 Linda Lindblad, Hantverkslaboratoriet, 46766 229 300

Träffen genomförs med ekonomiskt stöd från Nordisk-baltiska mobilitetsprogrammet, Vestfold fylkeskommune och Riksantikvaren.

DEPARTMENT OF CONSERVATION

A CHEMICAL APPROACH TO ANALYTICAL TAR IDENTIFICATION An Exploration of the Chemical Composition of Industrial and Traditional Produced Tars

Kiat Ileen Margaretha Bergen

Degree project for Master of Science with a major in Conservation 2017, 30 HEC Second Cycle 2018:1

A Chemical Approach to Analytical Tar Identification

Kiat I. M. Bergen

Supervisor: Jacob Thomas Degree project for Master of Science with a major in Conservation

UNIVERSITY OF GOTHENBURG ISSN 1101-3303 Department of Conservation ISRN GU/KUV—18/01—SE

UNIVERSITY OF GOTHENBURG http://www.conservation.gu.se Department of Conservation Fax +46 31 7864703 P.O. Box 130 Tel +46 31 7864700 SE-405 30 Gothenburg, Sweden

Master’s Program in Conservation, 120 ects

Author: Kiat I. M. Bergen Supervisor: Jacob Thomas

Title: A Chemical Approach to Analytical Tar Identification

ABSTRACT This thesis is a comparative study on the identification of tar with the analytical methods: thin layer chromatography (TLC) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR). The research aims to compare the tars with each other in order to identify them as identical, similar, or different based on specific identified chemical properties. Additional analysis was done with the Scanning Electron Microscope-energy Dispersive X-ray (SEM EDX) to identify additives in the solid-phased tars. The research contained 34 different tars and 7 fractions from the såide burning of Östergarn, Gotland. The TLC method was successful in distinguishing the tar source material, production method, and as far as possible the production location. The ATR FTIR method was able to recognise tars on the source materials and their state of matter, and the method was the most straightforward and fastest in producing results. For a more into depth analysis, the TLC method appeared most effective. TLC method has the most potential, and therefore it was concluded that this was the most successful method for tar identification.

Keywords: tar identification, tar, thin layer chromatography (TLC), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR)

Title: A Chemical Approach to Analytical tar Identification Language of text: English (GB) Number of pages: 130 3-5 Keywords: tar identification, tar, thin layer chromatography (TLC), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR)

ISSN 1101-3303 ISRN GU/KUV—18/01--SE

Table of Contents

1. Introduction ...... 1 1.1. Assessment of the Quality of Tar ...... 1 1.2. Aim ...... 3 1.2.1. Limitation ...... 4 1.3. Research Questions ...... 4 1.4. Hypotheses ...... 4 1.5. Structure of Thesis...... 5 2. Literature Research...... 7 2.1 Terminology ...... 7 2.1.1. Natural Produced Tar and Definitions ...... 8 2.1.2. Difference between Tar and Pitch ...... 8 2.1.3. Tar Definition ...... 8

2.2. Tar Production ...... 8 2.2.1. Coal Tar Production ...... 9 2.2.2. Traditional Wood Tar Production ...... 10 2.2.3. Industrial Production of Wood Tar ...... 15 2.3. Tar usage ...... 17 2.3.1. Early Uses of Wood Tars ...... 17 2.3.2. Wood Tar as a Medicine...... 17 2.3.3. Usage of Coal Tar ...... 18 2.4. Chemical Composition of Tar ...... 18 2.4.1. The Chemical Composition of Coal Tar ...... 18 2.4.2. The Chemical Composition of Wood Tars ...... 19 2.5. Previous Research of Tar Identification with Analytical Techniques ...... 24 2.6. Selecting the Methods ...... 26 2.6.1. Scanning Electron Microscope-energy Dispersive X-ray ...... 26 2.6.2. Selected method 1: Thin Layer Chromatography...... 26 2.6.3. TLC Technique for Tar Analysis ...... 27 2.6.4. Selected method 2: Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy ...... 27 2.6.5. ATR FTIR Technique for Tar Analysis ...... 28 3. Materials and Methods ...... 29 3.1. Tar Samples ...... 29 3.1.1. The Historical Tars ...... 30 3.1.2. Coal and Birch Tar ...... 30 3.1.3. Industrially Produced Tars ...... 31 3.1.4. Tars from Gotland ...... 31

3.1.5. Other Traditionally Burned Tars ...... 32 3.1.6. Tars with no Information ...... 32 3.1.7. Såide Fractions ...... 34 3.1.8. Sample Preparations ...... 35 3.2. Experiments ...... 36 3.2.1. Experiment Set Up of SEM EDX ...... 36 3.2.2. Technique of Interpretation for the SEM EDX Results ...... 37 3.2.3. Set up of the TLC experiment ...... 37 3.2.4. Technique of Interpretation for the TLC Results ...... 39 3.2.5. ATR FTIR Experiment Description ...... 41 3.2.6. Techniques of Interpretation for the ATR FTIR Results ...... 42

4. Result ...... 45 4.1. SEM EDX Results ...... 45 4.2 TLC results ...... 48 4.2.1. TLC Plates of Standard Samples ...... 49 4.2.2. Tar Samples stacked in RGB ...... 68 4.3 ATR FTIR Results...... 74 4.3.1. ATR FTIR Results in Spectra...... 75 4.3.2. Principal Component Analysis of the ATR FTIR Results ...... 79 5. Discussion ...... 83 5.1 Discussion of the results ...... 83 5.1.1. Discussion of the TLC results ...... 83 5.1.2. Discusssion of the ATR FTIR results ...... 87 5.2. Evaluation ...... 89 5.2.1. Critical Reflection of the SEM EDX method ...... 89 5.2.2. Critical Reflection of the TLC Method ...... 89 5.2.3. Critical Reflection of the ATR FTIR method ...... 93 5.2.4. Other Complications ...... 94 5.3. Future Research ...... 95 6. Conclusion ...... 97 7. Executive Summary ...... 99 8. References ...... 101 8.1. Non-printed Sources ...... 101 8.2. Printed Literature ...... 101 8.3. Electronic Sources ...... 104 8.4. Figures ...... 107

Acknowledgement

At this moment I would like to thank the many people that have made this master thesis possible. First of all thank you, Jacob Thomas, my supervisor during this project, whom read my various revisions and helped with the understanding of the analytical methods. Thanks to the Riksantivarieämbetet for donating the extensive collection of tars, without this the research would not have been possible. Thank you, Christina Persson and the entire crafts laboratory of the conservation department of the University of Gothenburg for introducing me to this project as well as funding and donating, and for the possibility to participate in the Nordic tar network conference of May 2017. I would also like to thank the Nordic tar network for all the information on tar and the possibility to include the fractions of the Östergarn tar. And last, thank you to all my friends and family who helped revise my thesis, helped translate Swedish texts, and endured me during this process and still managed to offer love and support.

1. Introduction

Throughout centuries, tar has been used in Scandinavian countries for the preservation of buildings and ships (Egenberg, 2003; Hjulström, 2006). The tar used in the Scandinavia was primarily produced from pinewood (Egenberg, 2003; Hjulström, 2006). The softwoods of the Pinaceae family, for example, spruces and pines, are predominantly found in the Scandinavian forests (Hjulström, 2006, p. 283). To protect the wooden buildings from the wet climate, tar was used for the waterproofing and preservation purposes (Egenberg, 2003; Hjulström, 2006). The easy access to the pinewood led the tar industry to flourish. Local communities created their traditions in producing tar. Due to the different traditions, various approaches to the production of tar evolved. These approaches can be traced to different geographical locations within Scandinavia (Private communications, 2017). The “recipes” for producing tar and how to utilize tar have been passed on from generation to generation via word of mouth (Nordic Tar Network, 2017). Consequently, a large amount of this information has not been collectively recorded (Nordic Tar Network, 2017). In recent years the demand grew to recover the lost knowledge, as historic buildings need to be re-tarred. This matter was stressed in the doctoral research of Inger Marie Egenberg. The tar layered on the wooden structures of the medieval stave churches in Norway was found to be deteriorating very quickly, making it essential to re-tar the structure every three years (Egenberg, 2003, p.1). To preserve the authentic appearance of the structure the correct tar needs to be used for the maintenance (Egenberg, 2003). Inevitably, to conduct the restoration correctly, the right tars need to be identified.

1.1. Assessment of the Quality of Tar In January 2016 the Cultural Heritage Board of Sweden (Riksantivarieämbetet, abbreviated as RAA) published guidelines for the quality assessment of tar. According to these guidelines resin rich raw pine material creates high-quality tar (Riksantivarieämbetet, 2016). The guidelines are specific about assessing pine tar, and it does so by examining its physical properties to determine if the tar is usable to re-tar a wooden structure (Riksantivarieämbetet, 2016).

The article Trätära: edömning a kvalitet starts out with explaining that the name of the tar can indicate the quality of it. Tars that are named dalbränd are considered the best tars; other names for this are torvedstjara or mildad tjära (Shenet, 2010). These tars are made in a tar pit or kiln from the pine tree stumps, the root area of the tree. The tars named stamvedstjara, which translates to English as trunk wood tar, is made from the whole trunk and the tree stumps of the pine tree. This type of tar is oven burned. The trunk of a pine tree contains less resin than the stumps, which makes the tar lesser in quality when the whole tree is used. Therefore, RAA claims that dalbränd tars are superior to stamvedstjara tars (Riksantivarieämbetet, 2016). Alongside the information that allows one to assess a tar based on the name, the RAA suggests assessing the tar visually, on smell, and by touch to test the

quality of the tar (Riksantivarieämbetet, 2016). These methods help determine which fraction the tar is and how well it will create a film coating (Riksantivarieämbetet, 2016).

These guidelines are constructive but neglect to address problems regarding the dalbränd term and how to match the quality of previously applied tar to a fresh tar. First, the term dalbränd can be given to a tar without the assurance that it was burned in a pit and without the assurance it is actually solely made from the stumps of the tree. The name is not legally set and therefore, a tar holding this name does not necessarily mean it is indeed a very high- quality tar. For instance, the dalbränd tar from Claessons, produced in China, their production includes the whole tree instead of limiting it to stumps. Based on the information of the guidelines this tar should be considered as a lower quality (private communication, 2017). Especially industrially produced tars that are named dalbränd carry this name for marketing reasons. Industrially produced tars are made in a retort for optimal production and this gives a different quality of tar (Fossum & Hussad, 1993, p. 1243). A retort is an industrialized oven, and has a controlled environment, which is not the case in a traditional kiln. Therefore, it is of interest to research the quality difference between the different dalbränd tars and the chemical compositions of these tars.

The second aspect that is not discussed in the guidelines, and is regarded as problematic is the tar selection for a new tar layer over an old one. This process requires the selection of the “right” tar. It is a complicated process to find a matching tar for historical tarred structures. The historic tar creates a unique visual appearance to the building to which the fresh tar needs to be matched. The difference in phases makes the comparison of contemporary liquid tars with the historic solid tar difficult. Another aspect that makes it difficult to find a proper contemporary tar to use for historic structures is that the decay of the tar needs to be taken into account, as this influences the appearance of the structure.

Tar burning is an art. In the tradition, the wood tars are produced outdoors in a kiln (Egenberg, 2003). Hence, many variables cannot be controlled, making each batch of tar unique. On the other hand, in the industrial production of tar, it is possible to monitor the quality and quantity (Egenberg, 2003, p.67-75). Therefore, it is a reasonable option for restorers to explore the possibility of industrially produced tar. To find an industrially produced tar that has similar qualities to the traditional tar, I propose to analyse the chemical properties of these tars and identify whether these properties are similar or even identical.

Assessing tars, based on the chemical properties requires a chemical analytical technique. Within the softwood tars, the production methods leave a unique chemical fingerprint that can be used to identify the tars (Bergen & Thomas, 2017) A variety of analytical techniques can be used to research the chemical composition of tars. Thus far research shows that the gas

chromatography-mass spectrometer (GC/MS) is a very successful technique to do so. Other techniques like thin layer chromatography (TLC), laser-induced fluorescence spectroscopy (LIFS), and different types of infrared spectroscopy have been explored for the identification of tar.

Throughout the past decades, tar identification methods have shown to be costly and not ideal due to several reasons (Font, et al., 2007, p. 121). Firstly, in the past tar identification has been done mainly by GC/MS, which requires access to a laboratory (Font, et al., 2007, p. 121). However, the buildings in the process of restoration can be located in very remote areas with only a limited number of existing laboratories. Secondly, the distance to practical workspaces and required tools to analyse the tar imposes further obstacles to the work process. Thirdly, the high costs of renting a laboratory and the needed machines make the known techniques unattractive. Thus, a technique that is field-deployable combined with lower costs would provide the restorers with an advantage in the restoration process. Consequently, any technique that meets these requirements is in demand.

1.2. Aim The research aims to find a suitable technique that can identify and classify the tar based on source material and production method. The suitable technique should ideally be deployable in the field, be affordable, and be reliable. The purpose of this thesis is to examine whether these different techniques thin layer chromatography (TLC) and Attenuated total reflection Fourier-transform infrared spectroscopy (ATR FTIR) provide results that can be interpreted reliably and to be considered a useful technique for the tar identification. The method is considered a success when tars that are identical, similar, and different can be identified based on chemical properties that have been linked to the source material and production method. Furthermore, the research aims to evaluate which of the established methods is superior, providing results in the cheapest, fastest, and most coherent fashion while not reducing scope and quality.

To research this aim, I propose to use the chemical properties of the tars that are considered good quality as a standard to which the other tars can be matched. For this a chemical fingerprint is made of the tars. In this way, good quality tars can be identified through their chemical properties. I propose to do this with the means of the thin layer chromatography (TLC) technique and explore the possibility of the Attenuated total reflection Fourier- transform infrared spectroscopy (ATR FTIR) technique. The TLC technique is selected for its easy use, the low costs, and comprehensible results. This method creates a fingerprint that exists out of several bands on a silica gel plate. The ATR FTIR technique has more costs and is laboratory bound. However, its advantage is that the results can be obtained fast and are easy to interpret. This method shows the fingerprint in the form of a captured spectrum. The spectra of the different tars are compared with each other. To gain additional information

about the tars that are examined with the TLC and ATR FTIR technique the Scanning Electron Microscope-energy Dispersive X-ray (SEM EDX) is used to detect additives in the tar samples.

1.2.1. Limitation This research does not aim to match certain contemporary liquid tars to specific historic solid tars. Instead, it merely explores the tools that can identify tars based on specific chemical properties that are defined within each specific research method. This research does not build a statistical model but aims to use interpretation techniques that give direct results by visual assessment. In case that statics are used, it is solely to illustrate that it is a possibility to analyse the results in that way. The tars included in this research can be utilized for comparison of future unknown tars.

1.3. Research Questions The following questions are answered in the literature chapter:

 What is tar?  What is tar used for?  How is tar produced?  What is known about the chemical composition of tar?  What is Thin Layer Chromatography?  What is Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy?

The following questions are researched through the means of the analytical methods in this thesis:

 What additives are found in the historic tars with the scanning electron microscope- energy dispersive X-ray?  Can Thin Layer Chromatography be used to identify tar?  Can the Thin Layer Chromatography create a fingerprint of wood tars?  Does one fingerprint have bands with a specific chemical composition that can be compared to fingerprints of other tars?  Can Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy be used to identify tar through creating a unique spectrum for the tars?

1.4. Hypotheses The research tests the following hypotheses:

Hypothesis 1: The thin layer chromatography (TLC) method successfully identifies tars that are identical, similar, and different.

Hypothesis 2: The Attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR) method successfully identifies tars that are identical, similar, and different.

When is the TLC method regarded as successful?

The TLC method is considered to be a successful method that identifies tars when it meets the following criteria:

1. Show a similar pattern of bands for all the pine tar. The bands that are similar can be used to distinguish pine tar from birch and coal tar.

2. Show a similar pattern of bands for all the tars with a similar production method.

3. It shows a unique band(s) for each tar. This single band pattern means that a pine tar that is traditionally burned in a small Gotlandic village shows a different pattern than a modern kiln burned tar burned on Gotland.

In the case that one of these criteria fails to be met, the TLC method is deemed to work unsuccessfully. If only some of these points are met, it might be worthwhile to further examine the method to see whether it can work with alterations.

What makes the ATR FTIR a successful method?

The ATR FTIR can be regarded as a successful method if it demonstrates that it is capable of the following points:

1. Show how a spectrum that shows similar peaks for all the pine tars. These peaks can be used to determine if a tar is made of pine or not.

2. Produce a spectrum with similar peaks for all the different production methods.

3. Finally, show a unique marker that can distinguish tars that are from the same source material and have the same production method but are not form the same geographical area.

In the case the FTIR does not meet all of these requirements, it cannot be considered successful. However, if some of these points are met, it can be stated that the ATR FTIR is solely successful in that specific identification of the tar.

1.5. Structure of Thesis The structure of the thesis will be set out in this section. The first chapter is the literature review. In this chapter, the terms and concepts that are used throughout the thesis are defined, and techniques behind the proposed techniques are explained. This chapter forms the theoretical framework of the research. This chapter also discusses the previous research that

has been done on tar identification. Following this, the third chapter will discuss the methods and materials, describing in detail the information about all the tar samples, the use of the SEM EDX, the setup of the TLC method as well as the interpretation techniques used with this approach, and the ATR FTIR setup and interpretation techniques. The fourth chapter shows the results of the SEM EDX, TLC, and ATR FTIR. The SEM EDX results are discussed alongside images of the tar. The TLC results are presented in images with explanatory text. The ATR FTIR results are presented in graphs and a cluster plot. The graphs show tars classified based on the raw material and the production method. These graphs are interpreted in the ATR FTIR discussion section, which is in the fifth chapter. The fifth chapter initially discusses the collective information that is gained from all the techniques, and this is compared to previous literature. Moreover, in this chapter, the hypotheses are tested. The sixth chapter, the final chapter, is the conclusion. Here, the research is evaluated, concluding remarks are made, and suggestions for future studies. After this chapter, the reference list and the appendices can be found. All the figures, photographs, and tables are authentic unless specified otherwise through a reference.

2. Literature Research

The production of wood tar in the Scandinavian countries has been a traditional craft that was transferred from generation to generation by word of mouth (Kathimmersvik, 2017 from notes). This oral tradition is therefore connected to the location. On May 29, 2017, the first meeting of the Nordic tar network was held on Gotland, Sweden. Gotland has had a long- standing tradition in tar burning (Kathimmersvik, 2017). Small villages on this island still uphold the intangible tradition of tar burning. At the Nordic tar network meeting the current issues surrounding tar were discussed. One of the issues that have led to the origin of this network was that the knowledge of tar had been become lost over time the fact that the tar production has hardly any written source on the local customs of tar burning. The network was established with the intention of creating a more collective knowledge of tar in which different parties are to benefit.

This chapter contains a section named terminology in where the various terms surrounding tar are defined. After which sections follow explaining the production of tar, the usage of tar, the quality of tar, and the chemical composition of tar. Continuing by discussing the previous research that has been done on tar identification with the means of analytical instruments. The closing section of this chapter focuses on the two analytical techniques that are explored in this research and substantiates how these techniques are logical choices for the identification process of tar.

2.1 Terminology Tar is a material that is made through the pyrolysis of either wood or coal (Mills & White, 1994, p. 59; Egenberg, 2003, p. 53). The Oxford English Dictionary definition on tar: “A dark, thick, flammable liquid distilled from wood or coal, consisting of a mixture of hydrocarbons, resins, alcohols, and other compounds. […].” (Def. 1, Oxford English Dictionary)

In the book The Organic Chemistry of Museum Objects of Mills and White, the substance tar is categorized under bitumen materials. This book states that bituminous substances have similar chemical components and physical appearance. The physical features ascribed to these materials are the black, dark brown colour and a noticeable smell. The tar material is liquid after production but becomes solid overtime (Mills & White, 1994, p.59).

The bituminous materials can be divided into natural products and human-made products (Egenberg, 2003, p. 58-74); Mills & White, 1994, p.59). The human-made products are produced through dry distillation. This technique is also named pyrolysis or destructive distillation. The solid source material is brought to boiling with limited oxygen present. The resulting liquid from condensation is referred to as the distillate, and the remaining substance

is called the residue. Within the production of some bituminous materials, fractional distillation is used, which means that the product during the production is separated through the condensation and evaporation at different temperatures.

2.1.1. Natural Produced Tar and Definitions In the literature about tar, the source material of tar is mentioned to inform the type of tar. Sometimes the term "softwood tar" is used. This term is a collective name for different tars made of softwoods like pines and spruces (Mills & White, 1994, p. 65).

2.1.2. Difference between Tar and Pitch The distillate liquid is referred to as tar and the residue as pitch. The meaning of the terms pitch and tar are sometimes referred to as the same thing. On occasion, a different meaning is attached to the words. An example is given by J. Font et al., in which pitch is defined as a product that is solely made from the pine resin and tar is distilled from resinous trees (Font et al., 2007, p. 120). The term pitch can be both used for the residue of the distillation and the material that is made from tree resin (Font et al., 2007, p.120; Egenberg, 2003, p. 54-5).

2.1.3. Tar Definition

The terms used in this research are defined in the following way. With the term “tar” is meant solely the distillate, which appears in this research as well as solid as in liquid form. The solid tar samples were from historic buildings. The liquid tars were donated to this research by various sources that are explained in more detail in the Methods and Materials chapter. The term pitch refers to the by-product of the wood tar production, which is the residue that is left. The residue left in the manufacture of coal tar is called coke (Aftalion, 2001; Deeshka Tab, 2013).

2.2. Tar Production Tar can be obtained through either traditional methods or modern techniques. The traditional manufacturing style for wood tars has a limit on variables that can be controlled. Industrial methods, on the other hand, are designed so the variables can be monitored for an optimised distillation process. Nowadays traditionally burned wood tar still exists alongside industrially produced tars, though industrially produced tar has taken a primary lead in the overall production (Egenberg, 2003, p. 75). Destructive distillation means that tar is burned in an oxygen free environment, an environment that can be created in a kiln or specialized oven. The industrial production of tar started around the 19th century (Egenberg, 2003, p. 67). Before this time the production was small and limited to wood tars (Egenberg, 2003, p. 67). The following sections discuss the production methods within the historical time line more into depth, starting with the coal tar production.

2.2.1. Coal Tar Production Coal tar is a by-product in the production of choke (Cosmetic Ingredient Review, 2008, p. 2). In figure 1 a hierarchical production tree is visible. Visible in the figure is that first the coal undergoes carbonization this creates the choke of natural gas and the condensation coal tars (Agency for Toxic Substances and Disease Registry, 2002). This coal tar is a dark brown semi liquid substance (Agency for Toxic Substances and Disease Registry, 2002). Other coal products are obtained through distillation, such as: tar, pitch, residue, and coal tar creosotes (Agency for Toxic Substances and Disease Registry, 2002). The pitch residue is a black solid residue (Agency for Toxic Substances and Disease Registry, 2002, p18.). The terms crude coal tar and coal tar creosotes are not used consequently according to the Cosmetic Ingredient Review and Agency for Toxic Substances and Disease Registry (Agency for Toxic Substances and Disease Registry, 2002, p. 18; Cosmetic Ingredient Review, 2008, p. 2). Coal tar as described in this thesis corresponds with the creosote coal tar of the Agency for Toxic Substances and Disease Registry. All the substances from the coal tars box in figure 1 have similar physical and chemical properties (Agency for Toxic Substances and Disease Registry, 2002, p. 19).

The coal tar production is a by-product of the steel industry and therefore it is hard to state in the quantity in which coal tar is produced (Agency for Toxic Substances and Disease Registry, 2002, p. 232). In Figure 1 a diagram of the manufacturing process of coal tar.

Figure 1 Flow of coal tar productions and by-products of the process. Derived from Agency for Toxic Substances and Disease Registry, 2002, p. 18.

2.2.2. Traditional Wood Tar Production This section discusses the traditional way of wood tar. First, a general description is given about the workings of a kiln, a specialised oven for the tar production. After this, the different local adaptations of burning are discussed. There are many different conventional ways since the traditional method is a local custom of different communities two traditions are discussed, the Scandinavian and the Turkish.

In the traditional way of obtaining wood tar, the tar is burned in a kiln. The appearance of the kiln can differ. For example, the kiln can be constructed on a hill. This way the tar will be drained with the use of a funnel. The kiln can also be set-up in a ditch. The figure 2 and 3 show different versions of tar kilns.

Figure 2 Traditional tar "dal" kiln on a slope

Figure 2 shows a kiln that uses the slope of a hill. This model also illustrates how the wood is packed together. In this specific illustration, the covering layer of the wood is peat, and it has a layer of fresh wood in between the peat and the tar wood. The clay is used to create the funnel form of the kiln.

Figure 3 A version of a traditional kiln 11

Figure 3 illustrates a tar kiln that is above ground. The outside covering layer exists out of wet leaves in this case. The wood is packed on a specific funnel formation that allows the tar to be drained through a pipe that leads to the tar barrel.

Figure 4 Different traditional tar kilns with different drainage systems drawing from Farbregd 1989 p.10-11 (Egenberg, 2003, p. 2006)

Another example is a particular wooden drainage system, visible in Figure 4 (Egenberg, 2003, p. 62-3). The tradition of a hillside kiln is a tradition still alive today according to Egenberg who interviewed tradition-bearers. The kilns are stacked with the wood that meets the criteria of the local community. The image 4 shows the Norwegian tar burners preparing the kiln. Locals that are burning pine tar have a preference for resinous heartwood material of the old stump pine trees that have been dead for a certain amount of years. This resinous wood in the pine trees is also referred to as tar wood (Egenberg, 2003, p. 59; Regert et al., 2006, p. 246). The number of years the trees are left to erode depends on the custom of the community.

The wood is chopped in pieces and is stacked in the kiln. It is important to stack the wood correctly. Otherwise, there is too much air between the wood pieces. The air contains oxygen, which should be avoided. The oxygen disturbs the pyrolysis, because it can cause blowouts creating a massive flame through the middle of the kiln burning the so-called "tar wood" (private communications, 2017). During the burning it is preferred to have a temperature within the kiln around 300 degrees Celsius (private communications, 2017).

A top layer is added to the wood with a material that will create the oxygen-free environment during the burning. This topcoat differs per tradition. The Östergarn tradition was to use a fresh layer branches and top this off with wet sawdust, visible in Figure 5. The locals explained that the local custom in the North of Gotland is to use wet seaweed (private communications, 2017). Egenberg reports that traditionally in Norway peat was used as a top layer (Egenberg, 2003, p. 84). The freshly produced tar is collected in a bucket or a barrel. The locals of Östergarn informed that the different fractions of the tar used to be kept in separate barrels, however, nowadays all the tar is collect in one barrel. The composition and quality of the tar differ per fraction (Egenberg et al., 2003, p. 221-241).

Figure 5 The construction of the kiln of Egenberg's research. "The FNN96 pile of wood under construction, like a three-dimensional puzzle" (Egenberg, 2003, p. 85)

This method can take up to days depending on the amount of wood and the size of the kiln (Egenberg, 2003, p.64). While the kiln burns, the people standing guard can test the amount of "tar wood" that still needs to burn by poking a stick into the kiln. When there is a lot of resistance, there is a lot of tarwood left to burn, with little resistance most of the residue of the wood has burned and turned into charcoal. The community of the såide kiln at Östergarn,

Gotland, reuse the charcoal left of the production to light the next tar burning session. The kiln of Östergarn is shown in Figure 6.

Figure 6 Såide kiln at Östergarn at the moment of lighting the kiln

Conventional production of tar is a tradition that most often is passed through from generation to generation. The transfer of information is done mainly orally, making it harder to find the local process on paper. Through the meeting on the 29th and 30th of May 2017 in Östergarn on Gotland of the Nordic tar network information about different traditions was shared. One of the customs of the såide kiln at Östergarn Gotland is to use fresh pine branches with wet sawdust as the top layer of the kiln. The top layer of the traditional method differs very much. It was said that in the North of Gotland fresh pine tree branches were not used instead seaweed was used. Alongside this, the tradition on the mainland uses peat as a top layer. The use of peat is also the custom in the Norwegian custom as Egenberg rapports (Egenberg, 2003, p. 58). Another specific element is the trees that are selected for the kiln. According to Monica Syversin, an active participant in the såide kiln burning, the pine trees with the right "tar wood" need to be cut and dry for 50 years (Syversin, 2017). The "drying" process does not require a dry environment, as this is the process in where the useless parts of the tree erode. The eroding procedure leads that eventually only the "tar wood" that is the resinous heartwood is left, and can be used to make tar. This tradition differs from the description of a traditional method given by Kurt, Kaçar, and Isik. The wood needs to be "dried" for 10-15 years in this Turkish tradition (Kurt, Kaçar, Isik, 2008, p. 616). These specific top layers of the kiln, the geographical locations, and types of trees in the environment are all aspects that contribute to the difference in chemical composition and distinctive fingerprints that can be connected to a site.

The tar kiln has different names depending on the geographical area. Each tradition has its name for the process and the specific equipment involved. The kiln in Gotland is called the såide (Private communications, 2017). On the mainland of Sweden, it is often referred to as a dal, dalbränd is linked to this term as dal referrers to the kiln and brand means to burn (Åbyhammar, 2016). The term dalbränd implies kiln burned tar. In the introduction is addressed how this term is very loosely used for marketing strategies since the name still carries the image of good quality tar (Riksantivarieämbetet, 2016).

2.2.3. Industrial Production of Wood Tar Around 1820 the tar production changed drastically (Aftalion, 2001, p.47). Previously tar was used for wood protection and produced on a small scale. The transition from traditional to industrial produced came once the manufacturing of specific aromatic compounds for synthetic dyes became of interest. England took the lead early on in the industrial production of tar, for it was able to isolate coal tar. However, other countries, mainly Germany caught up by the end of the 19th century. From that point on the European industry and the households started to depend on the coal products, which included the coal tar. The industrialisation of pine tar production took off at the end of the 19th century in Norway and with this the research on tar (Egenberg, 2003, p. 67).

The industrial pine tar is made mainly retort plants (Egenberg, 2003, p. 67; Reunanen et al., 1996, p. 118). In Figure 7 a vintage retort is shown. The retort is a distillation column.

Figure 7 Vintage retort with condensation tube that is cooled by water (Mendeleyev, 1897)

It is significantly different from the kiln because the retort plants do not have the biomass in direct contact with the heat source, which is the case in the kiln (Egenberg, 2003, p.68). In the industrial production, it is possible to collect all the condensation and by-products (Aftalion, 2001, p. 47). Alongside this, all the variables, including the temperature, are better controlled in the industrial production. Allowing for the tar to be produced in a more constant quality and quantity.

Through private communications, the company Auson explained that the dalbränd pine tar produced by them is done industrially because the traditional way is to labour intense (private communications, 2017). The dalbränd is oven burned with a lower temperature. The adaptation of temperature allows the use of source material other than the old more resinous stumps.

In the article Comparison of Tar Produced by Traditional and Laboratory Methods, Kurt and Isik describe a traditional Turkish method of production and a laboratory way. For this laboratory way, they use freshly cut parts of the tree. The stumps are dried in a room at room temperature. The pieces of wood are significantly smaller compared to the traditional way, as the parts are 2-4 cm. The temperature of the machine used to produce the tar is set at a range between 40 – 100 degrees Celsius. In this production, the solvents acetone and ethanol are added, making it a hydro-distillation. The time of the production lies between 2-12 hours. This description of a controlled tar production is one way of producing tar. The detailed

information of the traditional production technique of the samples in this research was not given to this extent.

2.3. Tar usage The use of tar throughout history is different for the types of tar. Even though fossil materials that occur naturally, like bitumen, coal, and asphalt have been used from early on (Egenberg, 2003, p. 56-7). The use of coal tar has only been a custom of the last two centuries (Aftalion, 2001, p. 47). Wood tar, on the other hand, has been around for centuries and has many different functions. In the upcoming section the functions of tar are discussed.

2.3.1. Early Uses of Wood Tars In the Paleolithic period, birch tar was used as an adhesive (Ribichini et el, 2011). Due to the fact it is water resistant in ancient times wood tars were used to waterproof domestic objects (Font et al., 2007). In archaeological findings, tar and pitch residue is found on shipwrecks, dams, storage tanks and amphorae (Evershed et al., 1985; Font et al., 2007; Levell & Peters, 2011). Tar was also used in the mummification process to embalm the bodies, as a mummy of 1500 BC in Egypt was found (Levell & Peters, 2011).

During the Middle Ages within Europe and later in the new world, nowadays the United States of America. Tar was used in the punishment (Levell & Peters, 2011). During the Middle Ages, it was used to punish thieves during crusades (Levell & Peters, 2011). In the USA it was used to punish tax and whiskey collectors and English officials (Levell & Peters, 2011). More recent usage of tar as a punishment is found in Ireland where in the 1970s women that were associated with English soldiers were tarred (Levell & Peters, 2011). The last report was from 2007 also in Ireland for the punishment of alleged drug dealers (Levell & Peters, 2011). The tar that was used for the sentence was heated between 30 – 180 degrees Celsius (Levell & Peters, 2011). Beside that the substance is hard to remove it also leaves burn marks on a human body (Levell & Peters, 2011).

2.3.2. Wood Tar as a Medicine It has also been noted that birch tar has played a role in medical treatments (Krasutsky, 2006, p.919; Baumgartner et al., 2012, p. 49). Alongside that it was also used as medicine, preserving food, and used to chew on (Baumgartner et al., 2012). It has also been noted that birch tar has played a role in medical treatments (Krasutsky, 2006, p.919; Baumgartner et al., 2012, p. 49). The medicinal use of tar was widespread during the 18th and 19th century through its anti-sceptic properties and often used in treating skin diseases (Levell & Peters, 2011).

Starting around the Middle Ages in Norway pine tar was used to for decorating and protecting the stave churches (Egenberg, 2003, p. 1-2, 5). The primary use for pine tar was waterproofing it was later that the use of tar started to expand from just protecting the wood to a decoration purpose. This change was apparent in the use of tar for the stave churches in Norway. From the medieval times, a law protects the churches by stating that every three years the stave churches in Norway are re-tarred. The outside appearance of the stave churches is very connected to tar, since the whole outside is tarred. This also makes the substance of importance for research to preserve these churches in a proper way. The pine tar that was used for decoration purposes has presumably soot and charcoal added to darken the colour.

2.3.3. Usage of Coal Tar Coal tar, on the other hand, made through destructive distillation of coal, is a product of the nineteenth century (Mills & White, 1994, p.59). Coal tar first appeared as a by-product in the industrial revolution of England, which learned to be quite useful (Aftalion, 2001, p. 47). Coal tar was in high demand for waterproofing materials to its use as a road binder. However, the demand was greater than the production at the beginning of the 19th century. This problem was solved through the dye industry, as it discovered a more optimised production process. By 1880 households and the industry became depended on coal and thus coal tar. This dependency led to an exponential growth in the knowledge of the tar production industry, especially since the other country within Europe did not want to be depended on the English tar production. During the 20th-century coal tar creosote was mainly used as a pesticide according to the Agency for Toxic Substances and Disease Registry (Agency for Toxic Substances and Disease Registry, 2002, p. 20). Coal tar is used in the production of medicine, dyes, artificial yarn, and in pesticides (Deeshka Tab, 2013). Levell and Peters report on the use of coal tar as a medicine, it was used in the 19th century without little knowledge on its toxicity (Levell&Peters, 2011).

2.4. Chemical Composition of Tar The chemical composition of coal and wood tars differs, and therefore it is addressed separately.

2.4.1. The Chemical Composition of Coal Tar The coal material is formed through a process in where vegetation the starting material. This plant material contains a high amount of aromatic lignin (Milles & Whites, 1994, p. 59). Lignin and humic compounds play a fundamental role in the decomposition of vegetation (Berg & McMclaugherty, 2003, p. 23). Coalification forms high-condensed structures from high molecular weight molecules (Milles & Whites, 1994, p. 59). These structures create different types of coal. The hardest coal is close to pure carbon structures (graphite). The pyrolysis of these materials forms lower molecular weight aromatic compounds like

polynuclear aromatic hydrocarbons, phenols, and heterocyclic, which eventually becomes coal tar. The higher molecular weight material that is not transformed during the pyrolysis into tar forms residue that can be identified as coke and coal pitch. The elements in percentage ratio in coal tar are found to be 48% hydrocarbons, 42% carbon, and 10% water (Bos & Jongeneelen, 1988; Environment Protection Agency, 1994). According to the Cosmetic Ingredient review over 10.000 compounds are detected within coal tar. Within these 10.000 compounds, 400 are identified as polycyclic aromatic hydrocarbons, of which only 17 are deemed as hazardous (Cosmetic Ingredient review, 2008, p. 1). Within these 17 hazardous polycyclic aromatic hydrocarbons some fall in the category of the carcinogenic 1B, meaning that these maybe cause cancer (Chemical Risk Prevention Unit, 2011, p.1). Table 1 shows the composition of coal tar in substance type per percentage. Coal tar is not soluble in water, but it is soluble in organic solvents like benzene (Budavari 1989).

Table 1 The composition of coal tar (Gosselin et al. 1984) Percentage in coal tar Type of substance

2 % – 8 % Light oils (Benzene, toluene, and xylene)

8 % – 10 % Middle oils (cresols, naphthalene, and phenols)

8 % – 10 % Heavy oils (naphthalene, and derivatives)

16% - 20% Anthracene oils (mostly anthracene)

± 50 % Pitch

Creosote components can undergo reactions in gas phase. An example of this the compounds may undergo an oxidation reaction that produces hydroxyl radicals (Atkinson, 1989). It is also noted by Atkinson that coal tar is reactive with nitrate radicals in the dark. It is therefore of importance to handle coal tar good ventilated environment (European Communities, 2003, p. 2).

2.4.2. The Chemical Composition of Wood Tars Wood-derived tars are more complicated, as many different types of trees can be used to produce tar (Mills & White, 1994, p. 59, 65). As well as from hardwood and softwoods tar is produced. Birch bark tar, a hardwood tar, and pine tar, softwood, are the most commonly researched tars due to their excessive use throughout the history in the Northern hemisphere (Egenberg, 2003, p.75-6; Mills & Whites, 1994, p. 65). The resin in the softwood trees is of utmost importance to produce tar (Mills & White, 1994, p.99). The trees of the Coniferae family are most often used for the manufacture (Mills & White, 1994, p.99). This family is divided into five subfamilies: Pinaceae, Cupressaceae, Araucariaceae, Taxodiaceae, and Podocarpaceae, the latter to hardly have any resin, which makes them less favourable to produce tar (Mills & White, 1994, p.99).

The research of M. Reunanen et al. included five different wood tars in its study on the chemical composition. The study reported the chemical composition of four softwood tars belonging to the Coniferae family and one hardwood tar (Reunanen et al., 1996, p.118). M. Reunanen et al. included: Finnish pine (Pinus brutia Ten.), Turkish pine (Pinus sylvestris L.), cedar (Cedrus libani A.), Juniper (Juniperus oxycedrus L.), which falls under the Cupressaceae family, and Birch (Betula verrucose Ehrh). The Pinus sylvestris is the source wood that is also used for the Scots pine, the type of pine researched by Egenberg (Egenberg, 2003, p. 76).

Many components in the tar correlate with the compounds found in the resin of the tree (Egenberg, 2003, p. 76). The resins mainly consist of compounds that belong to the chemical category Terpenoids (Mills & White, 1994, p. 95). Resins have noted to contain mono-, sesqui-, di-, and triterpenoids. Terpenoids are built up out of isoprene units that exist out of five carbon compounds, see figure 8 for the structure.

Figure 8 Isoprene structure (Wikipedia "Isoprene Structure", 2005)

Monoterpenoids C10 compounds

Sesquiterpenoids C15 compounds

Diterpenoids C20 compounds

Sesterterpenoids C21 compounds

Triterpenoids C30 compounds

Carotenoids C40 compounds

Polyisoprenoid (C5)n polymers

(Mills & White, 1994, p. 95)

Di- and triterpenoids do not often occur in the same plant (Mills & White, 1994, p. 95). Diterpenoids are the main constituents in Coniferae resins (Mills & White, 1994, p. 99). There are three main skeletons: primarane, abietane, and labdane (Mills & White, 1994, p. 99). Primarane and abietene are mainly acids and abundantly found in the Pinaceae resins. Egenberg states that these diterpenoids acids can be used to specify the tar source (Egenberg, 2003, p. 77).

The archaeological and medical community has researched the chemistry of the birch bark, the source material for birch tar (Krasutsky, 2006, p. 920). Birch bark extract is made up of a mixture of pentacyclic triterpenoids, lupanes, and oleananes. The chemical composition per birch Betula species differ. Krasutsky notes 38 scientifically recognised birch species. The triterpenoids are the most interesting and make up the significant part of the extract (Krasutsky, 2006, p. 920-1). Krasutsky in his article displays a table containing the significant triterpenoids that are overall found in the birch bark extractives. The triterpenoids are Betulin, Betulinic acid, aldehyde, Lupeol, Oleanolic acid, Oleanolic acid 3-acetate, Betulin 3-caffeate, Erithrodiol, and other minor triterpenoids. Triterpenoid betulin makes up over 70% of the chemical content of birch bark.

The chemical composition of softwood tars is synonymous to the resin that mainly forms the tar during the dry distillation (Mills & Whites, 1994, p. 65). The tar content just like the resin content contains acids primarily from the abietine series. The four fundamental components of pine tar are the diterpenoids: retene, abietic acid, dehydroabietic acid, and methyl dehydroabietate (Hjulström et al., 2006, p. 284). The ratio of methyl dehydroabietate to norabietatrienes, 1,2,3,4-tetrahydroretene, and retene is depended on the temperature and time of combustion (Mills & Whites, 1994, p. 65). As mentioned before the traditional production process of tar has a unique every time, thus the composition of tar will differ every time as well.

Figure 9 Reactions during a tar burning process. Abietic acid undergoes dehydrogenation and isomerization of the double bonds that forms dehydroabietatic acid. This acid is followed by carboxylation, the carboxyl is present through the presences of methanol, and this creates methyl dehydroabietate (Hjulström et al., 2006, p. 284).

In Figure 9 the abietic acid chemical reaction scheme is presented, as it would be for a standard and controlled tar production. In the case of an increase in temperature the diterpenoids undergo dehydrogenation, oxidation, isomerization of double bonds, and decarboxylation (Mills and White, 1994, p. 100; Egenberg, 2003, secondary ref. Beck, 1997, p.185; Font et al., 2007, p. 120; Marchand-Geneste & Carpy, 2003). Font et al. also report that the presence of methanol during the combustion leads to the formation of methyl esters, notably methyl dehydroabietic acid (Font et al., 2007, p.120). Font also reports that retene is the primary product that can be found when tar has been burned with a too high temperature (Font et al., 2007, p.120). The reaction that forms retene starts with abietic acid that undergoes dehydrogenation, forming dehydroabietic acid, which undergoes decarboxylation creating dehydroabietin. Through increased amortisation dehydroabietin generates retene eventually, the reaction scheme is visible in Figure 10 (Font et al., 2007, p.120; Marchand- Geneste & Carpy, 2003).

Figure 10 Reaction scheme of one pathway of abietic acid in accordance of the information of Marchand-Geneste & Carpy 2003

Through contact with the atmosphere, the ageing process of tar in the form of oxidation generates compounds like 7-oxo-dehydroabietic acid, and 7-oxo-15-hydroxy-dehydroabietic acid, alongside methyl esters (Font et al., 2007, p.120). Font et al., Reunanen et al., and Egenberg display in their research more detailed information about the constituents found in tar through analysis with a gas chromatography-mass spectrometer (GC/MS).

Egenberg gives accurate insight on the chemical composition of Scots pine tar. The tar contains these main compounds tricyclic diterpenoids, resin acids, fatty acids, phenols, and neutral constituents like tricyclic diterpene. The quantity of the resin is depended on the resin in the pinewood (Egenberg, 2003, p. 77). The primary resin acid for the pine tar is abietic acid (Egenberg, 2003, p. 78). The liquid tar contains an abundance of the dehydronated form of dehydroabietic acid (Egenberg, 2003, p. 77).

In the introduction the article of the Riksantikvarieämbetet Trätära: edö ning av kvalitet good quality tar is defined. This article states that the quality of pine tar is determined on the resin richness of the raw material. The more the pinewood contained resin, the better the quality of the tar (Riksantikvarieämbetet, 2016, p. 1). In the previous section was stated that

the ratio of methyl dehydroabietate to norabietatrienes, 1,2,3,4-tetrahydroretene, and retene is depended on the temperature and time of combustion (Mills & Whites, 1994, p. 65). Based on these compounds it is possible to determine the quality of the tar. Tar that is burned too hot contains more retene, and more retene correlates with a low-quality tar (Font et al., 2007). A high amount of abietic and dehydroabietic acids present relate to the tar wood being rich with resin and correctly burned (Mills & Whites, 1994, p. 65). Abietic acid is the chemical compound that needs to be identified with the analytical techniques.

Reunanen et al. note that compared to the softwoods the birch bark tars have a more substantial amount of water-soluble organic components (Reunanen et al., 1996, p.120). Alongside these elements, the birch bark tar has simple phenols, fatty acids, and dehydrogenated sterols that make up a significant part of the composition of the tar (Reunanen et al., 1996, p.120). Other research focuses on the high presence of triterpenoids (Mills & White, 1994, p. 65; Aveling & Heron, 1998). The triterpenoid diol betulin has been a known marker for birch bark tar that can even be detected by thin layer chromatography (TLC) (Mills & White, 1994, p. 65). In more recent research claims that betulin is not a reliable marker to identify birch as the source material for archaeological material since it is also present in birch bark, and for archaeological research a biomarker needs to distinguish residue of tar and just ordinary birch bark (Aveling & Heron, 1998; Hjulström et al., 2005,p. 284). In this research betulin can be used as an identifier for birch tar.

2.5. Previous Research of Tar Identification with Analytical Techniques Most research on tar and pitch comes from the archaeological field (Evershed et al., 1985; Heyek et al., 1990; Connan & Nissenbaum, 2002; Colombini et al., 2003; Hjulström, 2005; Font et al., 2007) Tar and pitch had numerous functions from waterproofing ships to more decorative usages throughout times (Egenberg, 2003, p.59). Research on identifying tar and pitch is in most cases done with the use of a gas chromatography-mass spectrometry (GC/MS) (Evershed et al., 1985; Heyek et al, 1990; Egenberg & Glastrup, 1999; Egenberg, 2000; Connan & Nissenbaum, 2002; Colombini et al, 2003; Hjulström, 2005; Font et al, 2007). The GC/MS shows to be an efficient method to get quick and very detailed information of small samples. Colombini et al. (2003) and Font et al. (2007) both explored the FTIR method. Non-archaeological research on tar focuses on the chemical composition of tar. Font et al. (2007) concluded that FTIR was a useful technique to analyse the samples to decide if into depth analysis is necessary. For into depth research Font et al. recommends the GC/MS method. Colombini et al. (2003) used the FTIR and GC/MS complimentary. Both techniques confirmed there was a resin of pine wood tar and pitch based on the presence of the diterpenoid acids with abietane skeletons that were found (Colombini et al., 2003, p. 666). The diterpenoids with the abietane skeletons were set as biochemical markers for the pine resin (Colombini et al., 2003, p. 665). The research does not try to determine if either tar or pitch was present, it merely states that the residue is of pine tar and pitch (Colombini et al., 2003, p. 666). Crawshaw (1997) explored the low-cost technologies Infrared spectroscopy

(IR) and Thin Layer Chromatorgraphy (TLC). Crawshaw (1997) does not evaluate on the usage of the IR method. In the research is shown that an individual IR spectrum of each of the tar samples is collected and enough to distinguish the tars from each other (Crawshaw, 1997, p.199-201). Research presented by Crawshaw did not include any images of the TLC plates. Crawshaw only discusses the measured retention factor (Rf) of the spots (Crawshaw, 1997, p. 198). Measuring the Rf of the spots can differ every time, and when the bands are too close together, it becomes hard to make any concrete conclusions. In the difficulties section of the article this is mentioned as well (Crawshaw, 1997, p. 198). The article ends with suggesting future research on the TLC is needed since this method could be used as an alternative method alongside GC/MS (Crawshaw, 1997, p. 201).

Hayek et al. (1990) cluster archaeological wood tar pitches (also known as just wood pitch) and contemporary produced pitches (Hayek et al., 1990, p.238). In the introduction, it states that around the 1960s several attempts were made to use techniques like infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and TLC to identify wood tar pitches (Hayek et al., 1990, p.2038). Unfortunately, all these sources are in German and not available online. Hayek et al. describe that these techniques used one specific chemical marker to determine the species of the tree used in production and that this was not a success. Hayek et al. state that the GC/MS is the best way to identify the tars, as the identification is based on multiple chemical components and through a principal component analysis (PCA) the wood tar pitches are clustered together based on compositional likeness in the research.

The archaeological research by Hjulström et al. (2006) uses four biochemical markers to determine the presence of tar at an archaeological site (Hjulström et al., 2006, p. 284). The chemical markers are retene, abietic acid, dehydroabietic acid, and methyl dehydroabietate (Hjulström et al., 2006, p. 284). Mills and White (1994) confirmed earlier that methyl dehydroabietate is an appropriate marker to use (Mills & White, 1994, p. 65).

Evershed et al. (1985) research was for the preservation of the Mary Rose, a shipwreck that was found. The wood of the ship appeared to be tarred, so to identify the substance Evershed used the diterpenoid hydrocarbons methyl dehydroabetate and dehydroabietic acid to identify which tar was present on the Mary Rose (Evershed et al., 1985, p. 529). The identification was made through the analysis of the historical sample with the GC/MS (Evershed et al., 1985, p. 529). The results were compared with the results of the contemporary produced tars that were analysed with the same machine (Evershed et al., 1985, p. 529). Based on the comparison the tar was identified as wood pine tar (Evershed et al., 1985, p. 529).

Research outside the archaeological field has also been done. Ingrid Marie Egenberg contributed significantly to the study on tar with her thesis on Norwegian tar traditions and

the tar maintenance of Norwegian stave churches (Egenberg, 2003). In her research, she reports on traditional tar burnings in Norway, the chemical composition of tar and the complexities that come with it, and the crucial aspects of the tarring maintenance of the Norwegian churches. In one of her research papers, she shows the difference in chemical composition of the tar fractions (Egenberg, 2000, p. 147, 149 – 154). The chemical analysis of her tar samples is done with a GC/MS.

Kurt et al. (2008) have researched the traditional tar burning of the pine type Cedrus Libanu A. in the south of Turkey (Kurt et al., 2008, p. 615). Their research aimed to report on the traditional methods of tar burning in the South of Turkey and the chemical composition of these tars (Kurt et al., 2008, p. 615). The chemical composition was analysed by gas chromatography-mass spectrometry mass selective detector (GC/MS-MSD) (Kurt et al., 2008, p. 616). Another study by Kurt and Isik was a comparative study on the chemical composition of tar when produced traditionally versus laboratory-produced tar (Kurt & Isik, 2012). This research found that the traditional and laboratory tar are different in chemical composition (Kurt & Isik, 2012, p. 81-2). There are many possible explanations for these differences. Despite the fact that there is a deviation in composition both traditional and industrial tars are used for similar purposes. Kurt and Isik state it is unknown if the working properties of these tars are the similar.

2.6. Selecting the Methods

2.6.1. Scanning Electron Microscope-energy Dispersive X-ray The Scanning Electron Microscope-energy Dispersive X-ray (SEM EDX) is a technique that is used carry out an element analysis on small selected areas (Stuart, 2007, p. 91-92). In a vacuum, the microscope sends a beam of energetic electrons to the sample this produces different signals (Stuart, 2007, p. 92). These signals are energy differences of the scattering electrons (Stuart, 2007, p. 92). In the case of the SEM EDX, the energy is released in the form of X-ray. The returning signals correspond to specific elements (Stuart, 2007, p. 92). This method is used in this research to detect the additives in the historic tars, because these additives contain other elements than carbon and hydrogen. This information is in addition to the TLC and ATR FTIR techniques and gives insight into the chemicals present in the historic tars.

2.6.2. Selected method 1: Thin Layer Chromatography Anthony Crawshaw explores the TLC method as a low-cost technique to analyse tars and pitches (Crawshaw, 1997). One of the benefits of this technique is the cost can be kept low, as various solutions and stationary phases can be used for this method. Depending on the mobile phase, the developing solvent, and the stationary phase it is possible to execute this TLC anywhere. The method works in the following way: the unknown substance in liquid form is

spotted on the stationary phase (for example silica) alongside a known standard. The stationary phase is often layered on a glass or plastic plate (Stuart, 2007, p. 298). This plate is placed in the developing solvent in an enclosed developing chamber. The mobile phase separates the substance on the stationary phase, creating a fingerprint of bands on the stationary phase of the chemical compounds. The bands (also called spots) can be compared with each other. Based on the comparison the chemicals that are presented as bands can be stated as different or the same. This comparison is done with the retention factor of the bands. This is the distance the bands travelled from the concentration line (the line were the samples were spotted) divided the overall distance between the concentration and the solvent line (the line where the solvent stopped after removing the plate from the developing chamber) (Stuart, 2007, p. 299). Bands on the same plate with the equal Rf are the same chemical (Stuart, 2007, p.299). Through the comparison of Rf’s TLC becomes a quick, easy, and fast analysis method.

Bands can be compared in another way than by comparing the Rf value, one other manner of this is with the means of an area analysis. In basic, the Rf value states that a chemical is identical when the bands are found at the same height on the plate. Through an area analysis of the RGB colour theory, each fingerprint gets its own colour, red, green, or blue. The bands are in this colour. The fingerprints of the tars are then stacked. The bands that are at the same location show a different colour. In the RGB colour theory if all the colours overlap it is shown in white. Two overlapping colours create a different new colour. For example, a red band of sample 1 and a green band of sample 2 that are at the same place show a band in yellow. This makes it very reliable to identify which bands are at the same location on the plate.

2.6.3. TLC Technique for Tar Analysis The chemical composition of tars is complicated and differs depending on various factors, for example, the production method, the temperature during the production, and the presence of oxygen (Egenberg, 2003; Reunanen et al., Mills & White, 1994). Therefore, the band structures that appear in the stationary phase are unique fingerprints that need to be connected with the specific factors of the tar. Based on similarities of the band structures between the tars can be concluded when tars are identical, similar, or different.

2.6.4. Selected method 2: Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR) technique provides the option to analyse the tar directly. This method is swift and easy to use. No preparation is needed, and within seconds the spectrum is visible on the computer. With a database, the computer can do the comparison and give results very fast. The ATR FTIR is bound to the laboratory, and the machine is on the expensive side. Due to the quick and easy

use, the technique was selected for this research. The infrared spectroscopy measures the infrared spectrum (Stuart, 2007, p. 110). This spectrum is defined by Barbara Stuart as: “An infrared spectrum is commonly obtained by passing infrared radiation through a sample and determining what fraction of the incident radiation is absorbed at a particular energy” (Stuart, 2007, p. 110). The energy is absorbed by specific elements of the molecule (Stuart, 2007, p. 110). These parts are the bonds that vibrate (either stretching or bending) (Stuart, 2007, p. 110). During this vribation the engery is aborbed (Stuart, 2007, p. 110). This shows as a peak on the spectrum (Stuart, 2007, p. 110). In this way, the ATR FTIR creates spectra for the tars that appear different in chemical composition.

2.6.5. ATR FTIR Technique for Tar Analysis Infrared spectroscopy was already used in previous research for tar analysis (Crawshaw, 1997; Colombini, 2003; Font et al., 2007). The ATR FTIR was available in the laboratory were the experiments were done. Based on the earlier use and availability this analytical method was selected for this research. The idea behind this technique was that the ATR FTIR catches the spectra of the tars, and that the tars that are similar show similar peaks in the spectra.

3. Materials and Methods

First this chapter gives a detailed description of the tars, after which the following section of this chapter describes, each method’s experiment set up and the reasoning behind the set up together with the techniques that are used to interpret the data. The methods were selected based on their usage in the previous literature that was described in the last chapter, and on the criteria for being low cost, easy and possibly in field usage.

3.1. Tar Samples Several parties, like the crafts laboratory of the Conservation department, donated the tar samples used in this study. Figure 11 shows an overview of all the tar samples. The samples are classified based on the information that was provided with the tar selection. These tars are discussed in the order of the classification scheme of Figure 11. Thus first the historical samples are addressed, then the coal and the birch tar, etcetera. All the tar samples and their corresponding number as it was used within this research are shown together in Table 2. In table 2, number 12 is abietic acid. This substance was used as a standard, which still needed a number within the research this is why it is presented among the other tars in table 2. Four historic tars are in their solid phases, whereas all the other tars in this research are liquid. These four tars will be referred to either by their name or as solid historic tars. The other tars will be referred to by their name or as liquid contemporary tars. Within the liquid contemporary tars there is a division between the industrial and traditional burned tars.

Hemse Kyrka

Ingatorp

Historic samples Spån Röros

17182

17189

Coal tar

Birch tar

tjätjära Cleassons Dalbrand Fin tjara

Industrially produced Biltema Äkta trätjära

Auson Äkta furu tjära

Alcro tjätjära

Dalbrand tjära Hemse

Ardetjära Burned 4 Juli 2004 Connected to Beck och Reps Fardhemstjära Burned 2 Juli 2011 distribution company Eketjära Burned 1996 Tar Samples Ethelhemstjära Burned Juli 2014 Tars from Gotland Bunge museet Burned in a såide Äkta Stusstjära Liquid tars Traditionally produced Såidetjära 2009 Pine tar Lokrums tjära 2006/7

Dalbrand tjära

Burned by Lapland, Norbotten Arvidsjaur tjära oskar Alexsson

Törnedals tjära

1814 without any info 1814 dalbrand 1814

pine tar

PR 2007

LG 2011 unknown FA 2011

Rödtjära

Vladimir Cukavac

Figure 11 Classification of tar samples

3.1.1. The Historical Tars The craft laboratory of the conservation department of the University of Gothenburg donated eight tar samples. The four historic tar samples were Ingatorp, Spån Röros kyrka 1780 –tal, 17189, and 17182. Besides the Ingatorp tar, the historic tars were still attached to wood to which it was applied. The Ingatorp sample was substantially smaller than the others. The two samples 17189 and 17182 seem to have come from the same structure, as the numbers are close in range, judging the tars on visual appearance they were considered as similar, and in the wood tar project, these samples showed very similar results (Bergen & Thomas, 2017). Gunnar Almevik donated the other historic sample of the Hemse kyrka. The wooden church structure dated back to the 1100th B.C., making this the oldest historical tar.

3.1.2. Coal and Birch Tar Both the coal and the birch tar were diluted samples. The diluent of the coal tar was unknown. For the birch tar ethanol was used to dilute the tar in a ratio 1:1 volume by volume.

Presumable, the coal tar was diluted in the same way. The viscosity of the tars was very watery, whereas tar is known to be viscous and has a black colour in a barrel (Egenberg, 2003, p. 53). Through ATR FTIR a slope of –OH was visible on the spectrum. Thus an alcohol is present in the sample. The coal and birch tar were provided in cylinder vessels together with the tar sample labelled pine tar by my supervisor Jacob Thomas. All three containers had a red lid. Through the volatile fumes of the coal and birch tar, the red cap started to melt. In the case of the coal tar, the red plastic began to mix with the tar sample. This contamination was not the case for the birch tar. The samples were transferred to a different container after the decay of the caps was discovered.

3.1.3. Industrially Produced Tars The industrially produced tars are the tars from larger companies. The four tars from the Claessons tjätjara AB firm were three dalbränd and a Finnish tar. The craft laboratory gave one sample of the dalbränd tar, and the Riksantivarieämbetet (RAA) donated the other tars. The dalbränd tar is manufactured in China, and the Finnish tar sample was made in Slovakia (Private communications). The other three industrially produced samples were from the companies Auson, Biltema, and Alcro. Thanks to the craft laboratory the Auson tar became part of this study and the other two cases through the donation of the RAA. The company Auson commented on the production methods, stating that the dalbränd tars were burned in ovens at a lower temperature than in a kiln. The low temperature allows the company to use other parts of the pine tree for a higher production output. According to Auson, this production technique creates similar properties for the tar. Of the Biltema äkta tjära is only the name known. The Alcro tar label stated it was a lacquer wood coating. Other information could not be deduced for this tar.

3.1.4. Tars from Gotland The term såide is only used on Gotland for a kiln. Thus the tars that were labelled with either såide or sojdet were categorised as tars from Gotland. Within this class, there is a division between tars that were connected to the company Becks och Reps and others. Becks och Reps used to be a distribution company located on Gotland. The website of the company does not exist anymore; this led to the conclusion the company does not exist anymore. The location of the company was known as it was stated on the label of the tars. All the tars from this category, except the tar called dalbränd tjära, were received from the RAA. The only information known about these tars is that the location of where the tar was burned is presented in the name. Thus villages like Lokrume, Hemse, Ethelhem, Fardhem, and Arde.

The tar labelled “dalbränd tjära från Gotland” was made by Bo Lautin in Klinthamn, a village located on Gotland (Bergen & Thomas, unpublished). Based on the location of where

these tars were made is concluded that the tars were burned in a traditional kiln by the customs of the villages. The customs are conserved as intangible heritage by the Bunge museum on Gotland. This Gotlandic museum placed a video of their tar burning on Facebook. From this video, it becomes clear the same technique was used in the tar burning of this tar as the tar of the Östergarn fractions (Bungemuseet AB, 2017).

3.1.5. Other Traditionally Burned Tars Under the category of other burned tar is the tar from the small town Arvidsjaur. This city is located in Norrbotten in Lapland. On the label of this tar was noted that Oskar Alexsson made it. There was no other information about how it was made. Stefan Kirkula made the Tornedals tjära. This maker initially made tar in a traditional manner, however, nowadays he has switched to a contemporary oven to burn tar. The Tornedals tjära is of the latter series. The other tars that are left in this category are the tars with the number 1814. This name refers to the year 1814. For the dalbränd 1814 tar samples was found in a shipwreck. Within the wreck, there was still a barrel of liquid tar. The other tar sample with just 1814 is presumed to be the same tar, especially since both have the same smell, like rotten meat.

3.1.6. Tars with no Information Through the visual and aroma assessment it was clear that the tars in this category are pine tars. The brown colour, and viscosity appeared similar as the tars that were known to be pine tars. Alongside the tars had a burned pine smell that made this identification possible. However, no description besides the information that is presented in image 1 was given with these tars. For the Vladimir Cuvakac and the rödtjara there are some speculations. The name Vladimir Cuvakac has linguistic roots in the names of Czech Republic and Slovakia (Private communications, 2017). Since the Claessons fin tar was made in Slovakia, it might be possible that this is a traditionally burned tar from that area of Europe. The rödtjara translates to red tar. On the website of Claessons it states that the red tar sold by them contains iron oxide create the red colour (Claessons, 2017). It might be possible that the same pigments were used for this tar.

Table 2 The names of the tars with the corresponding number in this research Number Name of tar

1 Inga torp tjärprov

2 Spån Röros kyrka 1780 - tal

3 17189

4 17182

5 Birch tar

6 Coal tar

7 Pine tar

8 Äkta furutjära Auson

9 Tornedalstjära

10 Dalbränd tjära from Gotland

11 Dalbränd Claessons

12 Abietic acid*

13 Dalbränd tjära Claessons

14 Äkta tjätjära Biltema

15 Dalstränd tjära Claessons

16 Etelhemstjära brunned in juli 2004

17 Dalbränd tjära Fin from Claessons

18 Vladimin Cukavac

19 Eketjära bränd 1996

20 Bunge Museets Äkta stusstjära from a real såide

21 Ardretjära burned on 4 July 2011 by the beck&Rep

22 Fardhemstjära bruned on 2 July 2011 by the beck&Rep

23 Alcro tjätjära lasyr trä

24 Sojdetjära 2009

25 Lokrume tjära 2006/7

26 Arvidsjaur tjära burned by oskar Axelsson

27 PR 2011

28 Rödtjära

29 LG 2011

30 FA 2011

31 PR 2009

32 1814

33 Dalbränd tjära 1814

34 Fintjära

35 Hemse Stave chitel ± 1110

3.1.7. Såide Fractions th st At Östergarn, Gotland, on the 29 -31 of May 2017 a såide, the Gotlandic word for kiln, was burned to produce pine tar. 7 fractions of this burning were sampled and sent in for this research to run them with the TLC method (Östergarn såide burning, 2017). Östergarn has a special såide in the forest with a stone underground. On this the pile of “tar wood” is carefully built (Östergarn såide burning, 2017). It is of importance that air between the wood pieces is limited. The wood is covered with fresh pine branches and wet sawdust. This limits the access of oxygen during the burning. Small holes in the sawdust cover are made, approximately 5, so the fire can be lit and spread equally. During the burning the holes are covered or opened to control the burning of the tar. The fire is lit with charcoal from the previous tar burning. With a stick the guards of the såide measure the amount of “tar wood” that burned. The stick is used to poke the pile of wood. With more resistance there is a still a considerable amount of “tar wood” left to burn. During the night of the 29th to the 30th of May there was a blowout, which burned the wood tar to hot and increased the whole temperature in the kiln (Östergarn såide burning, 2017). It was impossible to lower the temperature. Hence the tar was burned under conditions that were too warm.

The 7 fractions that are part of this research were taken at a different period during the tar burning. During a tar burning session a kiln produces tar in a time span of 4 days. The tar is captured in a bucket and then emptied in a barrel. Before the bucket was emptied a small sample was taken and labelled fraction X. Alongside this the time and the temperatur of the kiln at that time was measured. In Table 3 it states the time and the measured temperature of the kiln at the time.

Table 3 The såide tar fractions with time, date, and temperature of the kiln at the time. Fraction Date Time Temperature (C)

1. 29/5 23:00 92,80

5. 29/5 23:45 131,4

10. 30/5 00:46 214,15

15. 30/5 01:39 290,3

20. 30/5 02:59 474,55

25. 30/5 10:40 484,85

30. 30/5 18:30 483,10

35. 31/5 12:45 483,90

The fractions were spotted on the TLC plates and developed with two different mobile phases. These two different developing solvents were: the dichloromethane: hexane (2:3) ratio by volume, and ethyl acetate: hexane (1:50) ratio by volume. These tar fractions are part of this research to determine if there is a difference in TLC fingerprint when developed in different developing solvents. It also gives information about the difference between the chemical compositions of the fractions.

3.1.8. Sample Preparations The sampling of the historic tars was done with a gouge, tweezers, and a spatula. The samples were stored in glass vessels with a plastic lid. The vessels were weighed on an electric VWR scale, after which the tar sample was added. The weight of the tar in the vessel was for all the tars around 0,2 grams, with the exception of sample 13 the Dalbränd of Claessons had 0,024 grams. The samples and såide fractions for the TLC method were solved in 2 ml dichloromethane. The såide fractions that were developed in the ethyl acetate: hexane ratio 1:50 volume by volume were solved in 2 ml ethyl acetate. All solvents were added to the vessels by automatic pipette Finnpippette® (100 – 1000 μl). The samples and the fractions were left overnight. The following day only the tar samples were centrifuged to separate the soluble from the insoluble. The soluble was transferred to a new vessel by automatic pipette. The insoluble of the historic tar samples were prepped for the SEM EDX experiment. The

dichloromethane appeared to evaporate over time, thus before using the samples 2 ml dichloromethane was added so the samples were usable.

3.2. Experiments The interpretation technique, visual assessment, was used for the results of all the analytical methods. Per method the specific criteria for the visual assessment are stated.

3.2.1. Experiment Set Up of SEM EDX The samples were placed on sample holders that were coated with double-sided carbon tape. The insoluble fractions, the fractions of the samples that were solved for the TLC experiment, were scrapped from the centrifuged vessel with a spatula. Dentist equipment and a spatula were used to sample from the historic tar samples. After each sampling the equipment was cleaned with acetone. Two historic tars had some areas that was coloured differently. The Spån Röros kyrka 1780 – tal tar sample has white spots that were sampled separately and 17189 had red spots that were sampled separately. In Table 4 the tars and the reference number of the stub with the sample are shown.

Table 4 SEM EDX prepped samples Stub number Sample name

1. Insoluble fraction of Ingatorp

2. Insoluble fraction of Spån Röros kyrka 1780 - tal

3. Insoluble fraction of 17189

4. Insoluble fraction of 17182

5. Spån Röros kyrka 1780 - tal

6. Spån Röros kyrka 1780 – tal white spots

7. 17189 red spot

8. 17189

9. Ingatorp

10. 17182

Before entering the machine the sample were carbon coated. The coated sample holders were placed on a platform alongside each other. This platform was placed in the SEM EDX. With a camera in the machine it was possible to identify which sample was placed under the

microscope. Of all the samples an image of the site of interest was taken in magnification 200. To create a sharp image the auto focus and auto brightness/contrast was used. Once a sharp image appeared on the computer the analysis of the element was done on selected areas within the image. For each site of interest around 10 of these analyses were done. Each analysis showed the elements on that spot. 10 analyses in the site of interest create a clear image of the elements found in the sample.

3.2.2. Technique of Interpretation for the SEM EDX Results The SEM EDX shows the elements in the samples in spectra that show a peak for a specific element. These elements are just read from the results. In order to make sense of these loose elements through literature these specific elements were traced to a specific substance. Through visually assessing the historic tars as well it was possible to see if the substance was detectable with the naked eye.

3.2.3. Set up of the TLC experiment The whole set up of the TLC experiment, including the solving of the samples and fractions, was done in a fume hood. Other safety measures were that the executer of the experiment wore a lab coat and protection goggles. During the visualisation a UV lamp was used, to which all present in the room wore UV protection glasses as long the light was on. The process of the TLC experiment is visible in figure 12.

Figure 12 Process of the TLC experiment

The TLC plates used for the tar samples were glass silica coated with a concentration line and were 10 by 10 cm. The first plate contained all the historic samples plus the abietic standard. The other four plates had 8 samples spotted out, plate II, III, and IV had abietic acid present. To keep consistency in the amount of samples spotted on the plate V lacks the present of abietic acid. Table 5 shows an overview of the samples per plate.

Table 5 Overview of the samples on the plates. Plate Samples Spotted

A 1, 2, 3, 4, 35, 12 6 *12= abietic acid

The standard on the plate

B 5, 6, 7, 8, 9, 10, 11, 12 8

C 13, 14, 15 ,16, 17, 18, 19, 12 8

D 20, 21, 22, 23, 24, 25, 26, 12 8

E 27, 28, 29, 30, 31, 32, 33, 34 8

The samples were transferred onto the plates with a capillary tube of 20 μl. The developing solvent was dichloromethane: hexane in ratio 2:3 volume by volume. TLC plates spent 10 minutes in the developing chamber. The time was kept on an Iphone 5C. The developing chamber was a glass container with a glass lid.

The såide fraction used glass TLC plates layered with silica without a concentration line that were 10 cm by 20 cm. Two identical plates were made of the såide fractions. The fractions for the first plate were solved in dichloromethane. The fractions for the second plate were solved in ethyl acetate. In both cases the capillary tube of 20 μl was used to spot the fractions on the plate. One plate was placed in the developing chamber that contained dichloromethane: hexane in ratio 2:3 volume by volume. The other plate was placed in the chamber containing the developing solvent ethyl acetate: hexane in ratio 1:50 volume by volume.

The Artist multi spectral imaging camera (Art Innovation) was used to visualize the TLC plates in ultra violet fluorescence (UVF). The calibration setting of the camera in UVF was different per photo session. Table 6 shows the exposure settings per photo session. The exposure settings were changed as the camera was built up several times.

Table 6 The exposure time of each photo session per RGB colour in milliseconds Colour/photo session Plate A –D Plate E Såide fractions

Red 272 ms 673 ms 497 ms

Blue 21,5 ms 137 ms 209 ms

Green 50,8 ms 316 ms 148 ms

3.2.4. Technique of Interpretation for the TLC Results Visual Assessment

The purpose of this assessment is to determine whether this method can identify and distinguish tars. Hence it needs to show an identical band structure for the same tar, also known as the fingerprint of the tar samples. For tars that are classified as similar but not

identical the bands that are compared almost need to be identical. And finally for different tars, it should not show any similarities in band structure. The TLC plates were assessed with a UV Lammag lamp 366 nm-1 in a dark room. Only samples on the same plate were compared. The tar samples were selected for each TLC plate, based on the number that was given in the research. During the assessment the colour of the bands, location of the bands, shape of the bands, and order in which the bands appeared were taken into account. The tars with band structures that seemed identical on all these accounts were considered the same tar. The similar tars showed some variation in either the colour, shape, or location. However, for tars to be considered similar the order of the band structure needed to be a close match. One extra band or a band less categorized the tars in the similar category. More extra bands or different coloured bands placed the tars in the different category. The tar samples were considered different when compared it did not fit in with the requirements for the identical and similar.

Area analysis

According to the theory behind TLC when retention factor (Rf) value of the 2 bands of is the same, the bands represent the same chemical. The Rf value is measured by dividing the overall distance between the concentration line and the solvent line with the distance between the middle of the band and the concentration line. In principle to consider two fingerprints as identical, it has to have all the bands in the same location and about the same shape. In other words, the areas that are bands on the plate are the same. Therefore an area analysis was done. In this analysis each tar samples’ fingerprint was cut into an individual image. These images were stacked so the areas, the bands on the plate, of the samples either overlapped or not. Samples where the areas overlapped were identical, samples where the areas partly overlapped were categorized as similar, and samples where the areas did not overlap at all were considered different. The analysis was performed in the program ImageJ.

RGB Stacking

The program ImageJ allows 2 to 3 black and white images to be stacked in colour (RGB) this is called RGB stacked. It takes the 2 or 3 images and creates 1 new RGB stacked image in which the images are layered. Each image has a corresponding colour, which colours the white areas of the black and white image in the specific colour. For example, image A has the white parts of the image changed to red creating in theory a red and black image, and this for other images with either green or blue. The layered RGB images show the areas on the image where the colours overlap in a different colour. This analysis makes the comparison between the fingerprints of tars more objective and clear.

In the case of 2 images, image A transforms into a red and black image and image B into a green and black image. The RGB stacked image shows image A and B together. The areas

where the two images have overlapping areas are shown in yellow. This makes it easy to trace the areas that are overlapping, since these are yellow, the areas that are only on image A still appear as red and the areas that are only on image B are still green.

In the case of 3 images there are multiple overlapping scenarios possible. For example: image A appears in red and black, image B in green and black, and image C in blue and black. There can be overlapping areas of A, B, and C, these areas appear as white on the RGB stacked image. Areas where A and B overlap appear as yellow. In the areas where A and C overlap the area shows as magenta, and in the areas of B and C it shows in cyan colour. All the not overlapping areas of the images appear in the original transformed RGB colour.

If all the areas appear in the colour that indicates overlap of the areas, then the tars compared are identical. If the images show that most of these areas show this colour the tars are classified as similar. The tars are categorized as different when the indicating colour is not present or limited present.

In imageJ the fingerprint of each sample was cut into a separate image. Each sample image had 88 in width and 678 in height. The solvent line is used to align the images. The solvent line is chosen for it is constants on the plates. Some tars samples do have a band pattern that is slightly tilted. All images were in type 16-bit to create a black and white image. Based on the visual analysis samples that were categorized as similar were compared. The two or three selected images were opened in ImageJ and the function “stack in RGB” was used to create the RGB stacked image. The sample that is the first in the stack is shown in the red colour, the second in the green colour, and the latter in the blue colour.

3.2.5. ATR FTIR Experiment Description An Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR) alpha Bruker with the OPUS 7.0 software was used to collect to spectra. The sample in question was placed on the lens that is found on the sample platform. A nob then is placed on top of the sample to pressure it down on the lens. Once the sample was in placed the function “measure new spectrum” was clicked in the software and the spectrum appeared. Each spectrum was saved in the OPUS settings. The file was later exported to excel. In excel, the spectrums were recreated and placed alongside each other. One file was not correctly converted to excel, historic sample 4 17182. Luckily the PDF was able to display this spectrum. After each sample the sample platform and the nob were cleaned with ethyl acetate.

3.2.6. Techniques of Interpretation for the ATR FTIR Results

Visual Assessment

The OPUS software had an automatic peak function, to show at which wavelength the peak appeared. The peaks were selected automatically and manually. The automatic selection showed only one main peak. The manual selection high lightened peaks that seemed prominent. Therefore the spectra were compared through a visual assessment. The spectra were grouped based on the same criteria that was used for the classification scheme, figure 11. The spectra were evaluated on the shape for the visual assessment.

Statistical Analysis

The fingerprint area of the ATR FTIR spectra is between 1500 – 500 nm-1 (Stuart, 2007, p.118). The overlapping spectra in excel were used to determine which spectra were most alike. Based on these peaks classifications were made. The comparison of the peaks in excel was done through visual assessment. If two spectra had the same peak at the same wavelength it was assessed as similar, if this was not the case the spectra were classified as different. With the data of the ATR FTIR a PCA analysis was done on the fingerprint region of the spectra. All the values between 1500 – 500 nm-1 were placed in a datasheet. The PCA was done with the same settings as described in the PCA section of the TLC plates.

Normalization of the data

The ATR FTIR measured the absorbance of the tars. The measured values were standardized with z-scores. For the display of the spectra the z-score were altered. The values used for the PCA were the original z-scores. Some of these z-scores were below zero, to have the spectrum be above zero for the display, the minimum of all the values was taken and added to all the values. In this way the lowest value became zero. This was done for each spectrum, and each had its own lowest number. For example, sample 1 had the lowest number -1,058. To all the values of sample 1 in the fingerprint region 1,058 was added. For sample 2 there was a different number the lowest, so for this sample their lowest number was added to all the values.

Plotting the data

The spectra were made in excel. After the normalisation, tars that were classified on tars species, geographical location, and production methods, name, and unknown tars. These categorised tars were plotted together for an optimal comparison.

Statistics of the Normalized Data

The statistical software SPSS was used for the PCA. In SPSS the principle component analysis is named “factor analysis”. The settings of the analysis were:

Method: principle component

The “factor analysis” function gives the option for various analyses. The principle component analysis was chosen for reasons mentioned earlier.

Analyse: correlation matrix

The correlation matrix was selected as the correlation between the samples is of interest.

Extract: based on eigenvalue, eigenvalues greater than: 1

This is a setting by default in the SPSS software. Each component has an eigenvalue. The eigenvalue is a measure that shows the amount variance that is caused by this component within the data. A high eigenvalue explains more of the variance in the dataset. For the principle component analysis the component with the two highest eigenvalues are used and plotted in a graph.

Rotation method: Varimax

The rotation method is used to state the possible relation the variables have with one and other (Field, 2013). The software attempts to maximise the loadings on to one factor and minimizes it on another based on the relation. This makes the outcome clearer. The varimax was chosen as it sees all the variables as independent of each other and it makes it easier to visualize which variables are connected to which principle component. Through the latter it is possible to name the principle component, so to explain what the variance is based on.

Missing values: excluded cases listwise

The default setting is excluded cases list wise. This was not changed as the missing values were already replaced by the mean in excel. The SPSS datasheet did not hold any missing values.

To determine which samples could be used for a PCA a Kaiser-Meyer Olkin (KMO) and Bartlett’s test was done. If the KMO value was close enough to 1 together with a Bartlett significant value close to 0 the data was deemed appropriate to do a PCA. After this the decision on the number of components that would be included was made. This was done through the table of variance and the scree plot. The table of variance shows the eigenvalue of each component. The number of components is equal to the number of variables. The number of variables equals the number of samples. The components with an eigenvalue higher than 1 explain most of the difference within the variables. For example, in the case of 5 components with an eigenvalue higher then 1, there are 5 components that explain most of the variance (Field, 2012).

Instead of showing the cluster graph of the PCA alongside a biplot, a table that summarizes the information of the PCA. The point of the bi-plot is to make sense of the PCA plot (Chong Ho, 2015). The bi-plot shows the principle components as eigenvalues within the space of the variables (Chong Ho, 2015). Instead the values of the samples for each component are shown in a table, this was done in accordance with Andy Field’s book Discovering statistics using SPSS (and sex and drugs and rock 'n' roll) on “how to report PCA results” (Field, 2012, p. 671-673).

4. Result

4.1. SEM EDX Results The SEM EDX results are discussed through the images taken with the machine. The samples are discussed one by one. There are multiple images for each sample, because for each sample the insoluble fraction left from solving the tars for the TLC and the tar taken directly from the sample were put under the SEM EDX. The images show spectra points numbered, these are the places the SEM EDX measured from. The elements of these areas are mentioned in the text under the images. In some cases a different material appeared to be stuck to the historic tar. In these cases there was an extra sample taken from the tar to examine it under the microscope. In all the insoluble cases chloride was found, this is due to the fact it was solved in dichloromethane. To illustrate the appearance of the historic tars Figure 13 shows three historic tar samples that are still on the original shingle.

Figure 13 Three historical tar samples A) Spån Röros Kyrkan, B) on the left side 17182 and on the right side 17189

Figure 15 Ingatorp insoluble fraction with Figure 14 Ingatorp direct tar sample with magnification 500 μm magnification 200 μm

Figure 14 and Figure 15 show the magnified images of the Ingatorp sample. In both the direct and insoluble Ingatorp sample there are signs of the presences of sand. This is based on the high amount of Silica that was found in combination with different elements like calcium, iron, magnesium, and aluminium.

Figure 16 Spån Röros direct tar sample Figure 17 Spån Röros insoluble tar sample magnification 100 μm magnification 200 μm

Figure 18 Spån Röros insoluble tar sample magnification 200 μm

Figure 16, Figure 17, and Figure 18 show the magnified images of the Spån Röros church. The insoluble and the white spots of the Spån Röros sample both showed the presence of carbon. The presence of carbon suggests that the sample contains soot. In the pure sample the elements found were in correspondence with that of sand. Thus the historic sample contains soot and sand.

Figure 19 Direct sample of 17189 magnification Figure 20 Insoluble sample of 17189 magnification 300 μm 200 μm

Figure 21 Red spot on sample 17189 magnification 200 μm

The 17189 showed in all the samples many different elements that are related to different types of sand. The different smaller pieces of 17189 are shown in Figure 19, Figure 20, Figure 21. The red spot showed on one side of interest the element iron. It was not clear if the red spot was created through this or if the iron element was part of the sand particles.

Figure 23 Sample 17182 direct tar magnification Figure 22 Sample 17182 insoluble fraction 500 μm magnification 200 μm

The smaller pieces of sample 17182 are visible in Figure 23 and Figure 22. In both the samples there was some carbon found. Therefore it is most likely that the sample contains soot. As well as sand, to which most of the elements related. Most sites of interest contained calcium and silica.

Comparing the four historic tar samples there is a difference in element found. In all cases these elements are part of the chemical composition of sand. However, the sand found in the Spån Röros church contains different types of sand than found in the other samples. The samples 17189 and 17182 showed great similarities in the elements found. As in both samples copper, magnesium, iron, and chromium were detected. In the Ingatorp sample and the Spån Röros samples magnesium and chromium were not detect at any of the sites of interest.

4.2 TLC results The TLC results are presented through images and tables that explain the sample order on the images. After the tables the TLC results of the såide fractions in two different solvent systems are shown in UVF. The fractions are first described and then interpreted based on the difference that is found between the different fractions and the solvent systems. This is followed with the interpretation of the results. The interpretation is divided in the different interpretation techniques. The first technique of interpreting the results is the visual assessment. The second technique is a follow up of the first technique as two to three samples of the same plate are stacked together. In these stacks the RGB colour theory is used to determine which samples are most similar based on where the colours overlap. The last interpretation technique that is used is additional and explores the use of statistical analysis. This interpretation is based on the measured colours in relation the Rf’s of the bands. Through a principle component analysis determined which samples were most alike.

4.2.1. TLC Plates of Standard Samples The TLC plates, Figure 24, are displayed in UVF, so the bands are visible. On the plate there are see through small circles on the concentration line, each measured band, and the solvent line. These are the points where the Rf’s and the colour was measured. There are five plates and the sample order from left to right shown in the tables below Figure 24. Plate A shows the historic tars, plate B the tars with different source material, plate C with the locally burned tars from Gotland, plate D with the unknown tars, and plate E with a combination of different tars under which the tar 1814 that was found in a shipwreck.

TLC plates of the samples

A B

C D

Figure 24 TLC plates I-V in UVF light. A. Plate I with samples 1-4, 35, and 12 B. plate II samples 5-12 C. Plate III samples 13-19 and 12 D. Plate IV samples 20 – 26 and 12 E. Plate V samples 27 – 34.

The following tables correspond with the plate. Displayed in the tables is the sample order from left to right. The sample most left on the plate will be the first number in the table. The visual assessment of each plate is found after each plate’s corresponding table.

Plate A

Table 7 the sample order of plate A Reference number Name

1. Ingatorp kyrka

2. Spån Röros kyrka 1780 - tal

3. 17189

4. 17182

35. Hemse kyrka

12. Abietic acid

Figure 25 Plate A the fingerprints of the historical tars with concentration line and bands marked.

Table 7 the sample order of plate A shows the tars present on plate A. In Figure 25 plate A is shown with the major bands and the concentration line marked. A yellow line marks the concentration and solvent line. The red lines show the tops of the three bands of the abietic acid. All the samples have a band at the lowest (closest to the concentration line) red line. Sample 3 does not have a band with the middle red line, whereas the other samples do. The top red line marks a band with all the samples. To clarify the bands that are related to the compounds of the abietic acid the bands are outlined with red. Samples 1, 2, and 35 have a light blue luminous band at the middle red line. The red line is a parallel to the concentration line. Therefore the chemical composition of this band is the same for samples 1, 2, and 35. Closer to the solvent line it is clear that samples 1, 2, and 35 have bands with a different location, colour, and form.

Comparing the lower bands within the red lines, samples 3 and 4 have a different height for these bands and a different colour. The outlined bands in red for sample 3 and 4 are at the same location and illuminate the same colour, thus this is the same chemical compound. The comparisons between the different bands of samples 3 and 4 are made visible through the green lines. The tops bands align perfectly, and have matching colours. Thus these bands are the same chemicals. Only between the lowest bands between the green and first red line there is a difference in bands for these samples.

The Spån Röros (sample 2) is from 1780 and the Hemse church (sample 35) sample is presumably from around the 11th century. The age of the Ingatorp (sample 1), the 17182 (sample 4), and the 17189 (sample 3) churches are not known. Based on the similarities it is likely that the samples 17182 and 17189 samples are from the same building. The Spån Röros and the Hemse sample have more bands in common than if the samples are compared to the other tars on the plate. It is worth considering these specific chemicals are products of the tar degradation. Unfortunately the age of the wooden structure of the church does not imply that the tar is from the same period.

Plate B

Table 8 the sample order of plate B Reference number Name

5. Birch tar

6. Coal tar

7. Pine tar

8. Äkta furutjära Auson

9. Tornedalstjära

10. Dalbränd tjara från Gotland

11. Dalbränd Claessons

12. Abietic acid

Figure 26 Plate B mixed tars with marked bands

Plate B, shown in Figure 26, contains the tars with different source materials. Table 8 shows the exact order of the tars. The concentration and solvent lines in Figure 26 are yellow.

Comparison to abietic acid

The bands identified with the compounds in abietic acid are outlined with red. A straight red line is drawn from the top of a band of the abietic acid. Sample 5, 7, 8, 9, 10, and 11 have a band at the same height, as the red line shows. However, none of these bands show the same colour as the band of abietic acid. The top band of abietic acid is found in samples 7 and 11, this is based on the colour and the height on the plate.

Pine versus Birch and Coal

The birch tar (sample 5), and the coal tar (sample 6) show a clear difference in band pattern compared to the pine tars that are spotted out alongside them. The birch tar shows a band at the top and the bottom, whereas the coal tar only shows a small band that fluoresces little at the bottom. The birch tar has a different colour in the bands. The bands of the birch tar, sample 5, are less radiant in comparison to the pine tars.

Comparing the different pine tars

Samples 8 and 11 are both industrially produced tars, whereas samples 9 and 10 are made by more traditional ways. Sample 7 has no known information about where this product was created and how. The lower bands closest to the red line of these samples do not appear similar in colour, height, or shape in anyway. Even though it appears that some bands are at the same height, the colour and shape do not match. The bands that do appear similar in colour, height, and shape are lined with an orange colour, and these bands are found at the top of the fingerprints.

Plate C

Table 9 the sample order of plate C Reference number Name

13. Dalstränd tjära Claessons

14. Äkta tjätjära Biltema

15. Dalstränd tjära Claessons

16. Etelhemstjära

17. Dalstränd fintjära Claessons

18. Vladimir Cukavac

19. Eketjära bränd

12. Abietic acid

Figure 27 Plate C in UVF showing the fingerprints of industrial and traditionally produced tars.

In Figure 27, plate C is displayed with the concentration and solvent line in yellow, the tops of the abietic acid bands are marked with red lines, and the other major bands are outlined with a colour. Table 9 shows the names of the tars that are spotted out on plate C.

Comparison with abietic acid

Sample 13, the dalbränd from Claessons, does not have any bands within the red lines that mark the location of the abietic acid. From this it is clear that there are hardly any chemical compounds in common with abietic acid. The abietic acid is desired, as its presence is connected to the quality of the tar. The samples 14 to 20 all appear to have bands within the lines of abietic acid. However, the bands do not appear similar when assessed on the colour and shape of the bands. Sample 14, the tjätjära of Biltma, has bands that appear brownish. It is possible that the bands within the red lines still contain unsolved substances of the tar, since the colour is so brownish. The other samples seem to have a band with this brownish colour, but this did not run up so high as it did with sample 14. The colours and shapes of the bands of the samples 16, 18, and 19 are similar within the red lines. It can be stated that these bands are similar to the bands of the abietic acid. These three samples are the traditionally burned tars on the plate. The two tars left are sample 15 and 17, both Claessons tars. These tars have bands within the red lines, but based on form, colour, and radiance the bands are significantly different from each other and the bands of abietic acid.

Comparing the industrial tars

Sample 13 and 15 are both dalbränd tars from Claessons. The fingerprints of these two tars are very different. The lowest bands, closest to the concentration line, for the two samples are at the same location and therefore have the same Rf value. However, the colour, and radiance do not seem similar. The third Claessons tar on the plate is sample 17, the Finnish dalbränd tar. This dalbränd seems to have a more similar fingerprint to sample 13. In orange the bands of these two samples are outlined. Both have a band at the top of the fingerprint, and a few close to the concentration line. Sample 17 has two bands in the lower band structure that are not present in the pattern of sample 13. Based on the similarities it is very likely that sample 13 is a Finnish dalbränd tar.

Sample 15’s fingerprint seems to have more overlapping bands with the industrial produced tar of Biltema, represented by number 14. From the concentration line till the green band marks these two seems to have bands at the same location, with the same colour, and a likewise radiance. From the green marked area onwards number 14 has bands are a different location, making it very clear that this is where the two tars are different.

Comparing traditional tars

The three traditional tars marked with the numbers 16, 18, and 19 all have the same band pattern up till the green marked area. Within the green area there are some colours visible like green and brown, unfortunately these bands are not distinctive enough. On top of the green marked area sample 16 sets itself apart form sample 18 and 19 as the latter two show to have

two bands there, whereas 16 only has one clear band there. Sample 18 and 19 seem identical in the location, colour, shapes, and radiance of their bands.

Traditional versus industrial

The traditional samples 16, 18, and 19 have bands located at a likewise height as the bands of samples 14 and 15.

The green marked area in the fingerprints of samples 14, 15, 16, 18, and 19 shows small and slightly radiant bands.

Plate D

Table 10 the sample order of plate D Reference number Name Amount of bands

20. Bunge Museets Äkta stusstjära 11

21. Ardre tjära 13

22. Fardhemstjära 11

23. Alcro tjätjära lasyr trä 11

24. Sojdetjära 2009 13

25. Lokrume tjära 12

26. Arvidsjaur tjära bränd av oskar 12 Axelsson

12. Abietic acid 3

Figure 28 Plate D traditionally burned tars alongside one industrial tar.

Figure 28 shows the traditional burned tar, of which most are from Gotland, and one industrial made tar from the company Alcro as Table 10 explains.

Comparing the tars with abietic acid

Within the red lines all the samples have bands, the colour of the bands seems to be constant within the different samples. Only the band between the lowest red line and the yellow concentration line has different colours among the tars. The bands of the tars do not have a clear ending and blend into each other. This makes it hard to determine if the compounds presented by these lower bands are the same as displayed by abietic acid.

Comparing the traditional tars

The traditional made tars numbered 20, 21, 22, 24, 25, and 26 all have the same bands in the fingerprints. The orange lines are draw parallel to the concentration line to create margin to clarify which bands appear with the same Rf value, thus within the same margin. The orange lines close to the yellow solvent line show that the top bands all fit within the band boundary. Especially samples 21, and 22 are alike, and samples 20, 25 and 26. This is based on the slight difference in the form of the bands between these two groups. The lower bands of the samples 20, 25, and 26 have bands that form slopes. The slopes for sample 25 and 26 are outlined with pink. Samples 20 and 25 have two slopes within one band; one of these slopes is larger than the other. Sample 26 also has the sloped band at the same height. However, this sample has four slopes, two small ones each followed by a larger slope. Tar sample 24 appears as an outsider in comparison to these traditional tars. The extra bands in this fingerprint are outlined with dark green. The bands that the samples have in common are luminous in a different degree than sample 24. Also the colours of the bands of sample 24 are of a different kind.

Comparing the industrial to the traditional produced

Sample 23, the tar from Alcro, has its major bands outlined with light green. The bands of this tar do not appear similar to any of the traditional tars, based on colour and form. Some parts of the band appear on the same location as the bands of the traditional tars. This has the effect that these bands have the same Rf value, but taking the colour and form into account it seems hardly likely that it is the same chemical compound.

Plate E

Table 11 the sample order of plate E Reference number Name

27 PR 2011

28 Rödtjära

29 LG 2011

30 FA 2011

31 PR 2009

32 1814

33 Dalbränd tjära 1814

34 Fintjära

Figure 29 Plate E a mixture of unknown tars, dalbränd Finnish tar, and dalbränd 1814

Plate E, displayed in Figure 29, shows unknown samples from the Riksantivarieämbetet, the samples from the 1814 tars that was found in a shipwreck, and a dalbränd fin tjära. The numbering of plate E is shown in Table 11.

Abietic acid bands

Even though abietic acid is not spotted on this plate, the previous four plates showed consistency in the fingerprint of abietic acid. The three bands of this standard are located low at the concentration line. All the samples have bands between the concentration line and the first light green line. Within this margin the bands of the abietic would have been present. Outlined in red are the bands that have a similar with the distance from the concentration line as the abietic bands had on the other plates.

Comparing the known tars

First, this section discusses the comparison between the tars of which some information is known. These tars are: rödtjara (28), 1814 (32), dalbränd tjära 1814 (33), and fintjara (34). Of the 1814 and the dalbränd tjära 1814 was presumed the samples came from the same tar. The bands appear to be at the same location, within a similar colour scheme, and have a likewise shape. Therefore it can be stated that based on the similarities in chemical properties these two tars are identical. The red tar (28) shows a different fingerprint in comparison to the known tars. Some chemical properties outlined in pink and at the first green line appear to be at the same location on the plate. However, the majority of the fingerprint does not seem parallel to the other fingerprints. The Finish tar (34) shows similarities with the 1814 samples (32 & 33). The major bands these three tars have in common are outlined in red, green, and pink. The primary band outline in purple is the band in which the Finnish tar shows to be different from the 1814 tars.

Comparing unknown tars to known tars

The main bands with red, green, purple, and pink occur in the fingerprints of the LG 2011 (29), FA 2011 (30), PR 2009 (31), and fintjära (34). The purple outlined band has a different colour for the LG 2011 (29) and FA 2011 (30) tars than for the PR 2009 (31) and the fintjära (34) tars. Taking all the bands into account, the samples 29 and 30 are most alike and the samples 31 and 34 are similar. The tar FA 2011 (30) does have a green outlined band that has the form of two slopes, which none of the other tars have. The pink band is in the fingerprint of LG 2011 and FA 2011 a little lower in comparison to the other tars on the plate. This also contributes to the statement that these two tars are most alike. In the comparison of samples PR 2009 (31) and fintjära (34) the pink band is closer to the solvent line than that of the PR 2009 sample. These four samples are comparable on the primary bands. Within the four tars it is clear that the LG 2011 an FA 2011 tars are equivalent of each other and PR 2009 (31) and

fintjära (34) of one and other. There are still among all of these tars slight difference and therefore it cannot be stated that these tars are identical based on the chemical properties.

The tars PR 2011 (27) and Rödtjara (28) both have completely different fingerprints in comparison with the other six tars on the plate. The red and pink bands the tars do have in common with the other samples on the plate. However, the bands in between the red and the pink bands are limited. There is a lighter green used to outline the lower bands, in which these two tars seem to have some overlap in the location of the bands. Though, these green bands are not similar in colour and shape. The green band of the rödtjara has two slopes in its shape. Above this green band there are small bands fluorescing very lightly. These smaller bands also appear in the fingerprint of PR 2011 (27). However, these bands are only located between the first green line and the second green line, whereas the bands of the rödtjara (28) appear even above the second green line. The two tars have quite similar chemical compounds that come forth in this fingerprint, but there are also clear markers that set these two apart.

Comparing tars of focus

Other tars that are of interest to compare were the two tars from Hemse, a small village on Gotland. The historical tar from Hemse (sample 35) came from a shingle of the Hemse church. The wooden structure dates back to the 12th century. The liquid tar sample is more recent and made by the locals of Hemse (sample 22). As both samples share the location of Hemse these two tars were compared to see any particular chemical properties that the samples have in common. The two samples are shown beside each other in Figure 30.

Figure 30 Tars from the Hemse area, both historical and contemporary

Within the lower bands, close to the concentration line, the two tars have potential for presenting the same chemical properties. For the top bands it is abundantly clear that there is no resemblance. For a proper comparison these two samples need to be spotted out on the same plate, to assess if there are chemical properties in common.

4.2.2. Visual Assessment of the Såide Tar Fractions

The såide fractions were run in two different solvent systems. Figure 31, the plate displayed on the left shows the plate run in ethyl acetate solution and the plate on the right the one that was run in dichloromethane solution. The later fractions, from fraction 20 onwards show an increase in the number of bands. This is visible on both images. After the 15th fraction the såide kiln started burning at a too high temperature. According to the literature this leads to the presence of dehydroabietic acid, dehydroabietin, and retene (Font et al., 2007, p.120). It is very likely that the bands that appear in the latter fractions correspond with these chemical

Figure 31 TLC plate of the Sande såide burned tar. A. Fractions in dichloromethane: hexane (2:3) solvent system, from left to right samples 1 - 35. B. Fractions in ethyl acetate: hexane (1:50) from left to right samples 1 – 35. compounds. The two solvent systems do show a different band pattern for the fractions. From this can be concluded that depending on the solvent system different chemical compounds are dragged up with the solvent.

In Figure 31 the fingerprint of the tar fractions are visible. Fraction 1 is the earliest fraction and together with fraction 5 were harvested on the first day. Fractions 10 – 30 were harvested the second day, and fraction 35 on the last day. During the burning of tar it is preferred to have the temperature around 300 °C (Kurt & Isik, 2012, p.78). Unfortunately during the first night there was a blow out, burning a lot of “tar wood” and increasing the temperature. The temperatures after this were all around 450 °C, which is too high. The first two fractions 1 and 5 were tapped when the temperature in the kiln was still reasonably low around 130 °C. Fractions 10 and 15 were close to 300 °C, a preferred temperature. It is most likely that this affect the chemical composition of the tar fractions. The next day the latest tar fractions did

not have the burned tar smell. This tar smell was present in the first few fractions. Looking at the fingerprints of the fractions, from fraction 25 there is a clear increase in bands in the middle. J. Font et al notes that retene is produced when the tar is produced at higher than the normal 300 °C temperature. Investigating if any of the bands, which appear in the later fractions, is retene is worth researching further. The fractions 20 to 35 all burned with a temperature around 450 °C. The tar samples seem to be more fluorescence on the image, this is due to the UV lamp being placed on that side and not lighting the TLC plate equally.

In the paper by Egenberg et al. “Characterization of traditionally kiln produced pine tar by gas chromatography-mass spectrometry” a notable difference between the chemical composition of the early fractions and the later fractions is found. The band patterns of the different fractions, 1 being the earliest fraction and 35 the last, show a significant difference. This difference might also be that temperature in the kiln had a blow out of fire during the first night, causing the temperature of the whole kiln to stay above 300 degrees after that.

Figure 31 allows the comparison between the two solvent systems. Plate A is the dichloromethane: hexane (2:3) solvent system and Plate B is the ethyl acetate: hexane (1:50) solvent system. The band structures that appear on both plates are very similar, and no major difference between the band structures can be noticed. However, the TLC plate B proved to show the bands in a bit more detail and more separated from other bands. It also shows better the fluorescent colours. The ethyl acetate solvent system takes longer to develop, but if the plate is placed in the right angle it does not have to take longer than half an hour for a small plate of 10 cm high. The ethyl acetate: hexane (1:50) solvent system is also less hazardous to work with.

Figure 32 TLC plate of the såide burned tar. Fractions in dichloromethane: hexane (2:3) (v/v) solvent system, from left to right samples 1 – 35 with band markings

Figure 32 shows the plate that was developed in dichloromethane: hexane (2:3) in a ratio volume by volume in which the major bands have been outlined and reference lines are drawn to make an accurate comparison of the location of the bands. Starting at the bottom bands close to the yellow concentration line, the latter fractions all have a band that is marked with orange. This band is not present in the earlier fractions. The early fractions seem to have a band that is marked with pink. The pink bands are located a bit lower than the orange ones.

At the green reference line all the fractions appear to have a band. This band’s location, colour, and shape seem identical for each fraction. Only the radiance of the latter fractions seems brighter than the early fractions. Also all the fractions have the purple marked band right above the green reference line and an identical band at the blue referencing line. The significant difference is made visible by the red marked bands that appear only in the fraction of 25 onwards. From all this can be stated that there is a difference in the fingerprint of a fraction, but there are chemical properties that are present in each fraction.

4.2.2. Tar Samples stacked in RGB For a more into depth comparison of the samples the RGB colour theory is applied to stack two to three samples. Based on the likeness of the tars in the visual assessment the following images were created in where the samples are stacked in RGB. All the samples that are

stacked are from the same plate, except for the stack where samples 3, 4 and 5 are stacked. This stack contains the two historic samples 17182 and 17189 and the liquid birch tar. The other samples were selected on the likeness based of the visual assessment. The RGB stacks are discussed under the image. The images show multiple stacks, each image shows stacks of one plate.

Figure 33 The tars of plate A stacked. On the left stacked samples 1, 2, and 35. On the right stacked samples 3, 4, and 12.

Plate A

Figure 33 shows on the left sample 1 as red, sample 2 as green, and sample 35 as blue. The white area is where the samples overlap. Sample 2 has the most number of bands. Both sample 1 and 2 have a shared band area at the bottom of the band structure bands in the form of a two-slope shape. The band for abietic acid is one of the lower bands. Samples 1 and 2 are known to be pine wood tar, thus abietic acid must be present. It is very likely that the overlapping area of the three samples is the band for abietic acid. The abietic acid band of that plate does appear on the same location. It does have a more concentrated band area. The spotting on the plate influenced the shape of the band, thus the shapes cannot be expected to

be identical. However, the location and estimate area of the band is of value for identifying identical bands. The in the right image are the bands of sample 3 red, sample 4 green, and sample 12 blue. There is a small cyan area meaning sample 4 and sample 12 have an overlapping band area. The image shows mainly that sample 3 and 4 have the same number,

Figure 34 Stacked images of plate B. Left image is samples 3, 4, and 5 stacked in RGB. Middle image is samples 7, 8, and 11 stacked in RGB. Right image is samples 9, 10, and 11 stacked in RGB. location, and luminous area of bands. This is visible by the green/red lines that are yellow in the middle. There is no clear indicator that abietic acid is present in sample 3 and 4.

Plate B

The first image in Figure 34 from the left shows the samples 3 and 4 from plate A stacked together in RGB with sample 5 from plate B. Sample 5 is the liquid birch tar and this was compared with the sample 3 and 4 because there was no clear indicator that abietic acid was present. The band structures of samples 3 and 4 seem to overlap, however, no matching areas are visible between these samples and sample 5. There is the issue that the samples were not on the same plate, which makes the comparison questionable. However, with the known Rf values it shows quite clearly that sample 5 has a very different band pattern from samples 3 and 4. The other images of figure 5 show stacked samples solely from the same plate. The middle image shows the bands of sample 7 in red, sample 8 in green, and sample 11 in blue. There are some white areas in at the bottom, however it seems like the bands mainly cover different areas. The magenta coloured area is where the bands of sample 7 and sample 11 overlap, the yellow areas is where sample 7 and 8 overlap, and the cyan areas is where sample 8 and 11 overlap. The green colour that corresponds with sample 8 covers most of the plate.

Figure 35 RGB stacked samples from plate C on the left samples 13, 17, and 12, the middle left shows sample 14 and 15, the middle right shows samples 16, 18, and 19, and on the right shows samples 16, and 18.

This is understandable as sample 8 covers a larger area with the lower band pattern, than the other two samples. Out of the three samples, samples 7 and 11 seem to be most alike. Both the magenta and the white areas appear as matching areas for the samples 7 and 11, and these colors are dominant on the image. The red bands in the right image are of sample 9, the green from sample 10, and the blue from sample 11. The images lack concrete white areas. The bands of sample 11 are covered by sample 10. It might be possible that the bands of sample 11 are also present in sample 10. This needs verification of the measured colour of the bands. Sample 9 and sample 10 show slight overlapping areas in the lower bands, but the fingerprint overall of the three tars is unique.

Plate C

The first image in Figure 35 shows on the left samples 13, 17, and 12. The bands of sample 13 are green, of sample 17 blue, and of sample 12 red. There is a small area of white of overlap at the concentration line of the plate. This is surrounded with cyan blue. The first band of sample 13 and 17 seems to overlap, and the top band overlaps slightly. Sample 12 that is in red seems to have other areas on the plate that do not seem to overlap with the two other bands. There seems no concrete area that is similar, it can therefore be stated that based

on the area analysis the samples 13 and 17 are considered different. The image next to it shows samples 14 and 15 stacked. Sample 14 is red and sample 15 is green. The overlapping areas colour yellow. The bottom bands of the plate are completely yellow. There is a difference in covered area in the top bands, as they do appear to have the same structure but they are placed next to each other instead of on top of each other. Sample 15 has more bands that continue after the last band of sample 14. Based on the area analysis the two samples are considered similar. The middle right image shows the samples 16, 18, and 19. The red coloured bands are of sample 16, the green of sample 18, and the blue sample 19. The bands on the images appear white, except for two areas of a slope in the first band. This means that the band shape of samples 16, 18, and 19 is similar. The band shape of samples 16 and 18

Figure 36 Samples from plate D RGB stacked. The left is samples 20 - 22, the middle is samples 23 and 24, and the right is samples 25 and 26. appear identical, as the yellow areas means that they overlap, and they overlap in the white areas. It is also visible in the image on the far most right where only sample 16 and 18 are stacked. Here the band areas are completely yellow.

Plate D

Samples 20, 21, and 22 displayed stacked together in RGB on the far most left image in Figure 36. The bands of sample 20 are red, of sample 21 green, and sample 22 blue. The image shows only white colour bands, thus the sample areas of 20, 21 and 22 are identical.

The middle image shows sample 23 and 24 together. Sample 23 shows its bands in red and 24 in green. The bands are shown in yellow, except for one band in red that appears above the yellow band structure. Based on the area analysis the two samples have similar band structures, but a difference can be made based on this extra appearing band of sample 23. The image on the right shows samples 25 and 26 together. The bands of sample 25 are red and those of 26 are green. The band areas align almost perfectly, since most of the band areas colour yellow. Only sample 25 has an extra slope in the middle of the band structure.

From all the samples stacked in RGB the samples displayed in Figure 36are by far the most identical. Especially the three tars stacked in the left image of Figure 36. The samples on plate D are all traditionally burned tars that come from the Gotland area, with the exception of sample 23, which is an industrial burned tar from the company Alcro. Sample 23 also appears to have an extra band in comparison with sample 24 a såide burned tar from 2009. The lower bands of which is known that the bands of abietic acid are there seem to be identical. It is thus most likely that the quality of the two tars is similar. The tars on this plate are high quality tars according to the RAA guidelines, because all the tars seem to contain abietic acid.

Figure 37 De samples of plate E, samples 27-34 stacked. The yellow shows overlapping area. From left to right, first image is sample 27 and 28 stacked, next is samples 29 and 30 stacked, following by 32 and 33 stacked, and on the far right 31 and 34 stacked

Plate E

Figure 37 shows the images of the stacked samples in RGB, since the samples based on the visual assessment looked less similar the images only show two samples stacked. The far left shows sample 27 with its bands in red together with sample 28 in green. These two samples are clearly very different since there are no overlapping areas. Sample 28 is an rödtjara, a red tar, to which pigments have been added. It is beneficial that is shows a completely different band pattern from sample 27, since sample 27 is a traditional burned tar from the town Lokrume. The middle left image shows sample 29 in red and sample 30 in green. The bands seem similar except for the top bands. Of these two samples was nothing besides an abbreviation was known. The middle right displays sample 32 with its bands in red and sample 33 in green. All the areas colour yellow. There is some shift more to the left for sample 32. Overall the bands appear on the same location and have a similar shape. Thus based on the area analysis these samples are similar. This matches with the expectations that the two tars come from the same source. Sample 32 is named 1814 and sample 33 was labelled dalbränd 1814. Through the overlapping band patterns it is very clear that the two samples are the same batch of tar. The last image on the right shows sample 31’s bands in red and those of sample 34 in green. This image shows clear yellow areas. The alignment of the bands is not perfect but enough to conclude that the areas are similar. Sample 31 is one of the unknown samples. Sample 34 is known to be a Finnish tar. Through the similarities it is very likely that sample 31 is also a Finnish tar.

4.3 ATR FTIR Results The ATR FTIR results are divided in two sections. The first section displays the spectra of the normalised tars and discusses the interpretation of these spectra. The second section shows and discusses the results of the PCA with the normalised tars. The normalisation in the first section had an extra step, as the values were marginalised to have all the values of the Z-score above zero.

4.3.1. ATR FTIR Results in Spectra

Graph 1 The spectra of the historic tars.

The historic tars of the Ingatorp church (sample 1), the Spån Röros church (sample 2), 17189 -1 (sample 3) and the Hemse church (sample 35) show a similar spectra from 3500 – 1380 nm , after 1380 nm-1 the spectra are completely different, visible in Graph 1. All the samples show distinctive peaks around 3000 nm-1 and 1690 nm-1, there it based on the 1690 nm-1 peak it can be presumed all are pine tar samples. In the fingerprint region between 1500 – 500 nm-1 all the tars appear to have a unique fingerprint.

Graph 2 The spectra of the Industrial tars

The spectra of the industrial tars that are shown side by side in Graph 2 all show a similar structure. Sample 15 and sample 8 have a peak around 1100 nm1 appears to be higher than the rest of the samples. For the rest the spectra are too similar to make a noticeable difference. Therefore it is of importance to do a further analysis on the fingerprint region, to determine to which extent the ATR FTIR is able to distinguish these tars.

Graph 4 The spectra of the tars from Gotland

Graph 3 The spectra of the dalbränd tars

The tars produced on Gotland, Graph 4, and the dalbränd tars, Graph 3, show the samples’ spectra as even more alike than the industrial spectra. Even in the fingerprint region the samples seems to show peaks at the same places.

Graph 5 The spectra of the tars with different raw material. Sample 5 is birch tar, sample 6 is coal tar, and sample 7 is pine tar.

Compared to the previous spectra, the samples of Graph 5 stand out. The samples 5 and 6 appear to have identical spectra. It is known that these tars were diluted. This explains the big slope around 3400 nm-1, which corresponds with the –OH stretching of the alcohol. The birch tar was diluted ratio 1:1 volume by volume with ethanol. It was unclear which alcohol was used for the coal tar. Based on the identical appearance of the spectra it is assumed that ethanol was also used for the coal tar. J. Font et al and Crawshaw state that there must be a peak around 1690 nm-1 for the tar to be wood derived. This peak is clearly missing at the coal -1 tar sample, the birch tar sample shows a peak around 1700 nm . The rest of the spectra of the coal and birch tars are still very different from the pine tars. The birch tar has it strongest peak around ± 1045 and ± 880 nm-1, and hardly any peaks between 2000-1500 nm-1. The coal tar has the strongest peaks between 1600 – 500, and no peaks around 3000 nm-1.

Graph 6 Spectra of the unknown tars, a Claessons Dalbränd tar, and a såide burned tar

Graph 6 shows the spectra of the tars with the least amount of information together with the spectrum of the Claesson dalbränd tar, and a såide burned tar from Gotland. The unknown tars spectra were placed along these known tars for a comparison with industrial and traditional produced tar. Outside the fingerprint region >1500 nm-1 the spectra of all the tars appear the same. Within the fingerprint region sample 28, the red tar, shows a different peak structure from the other tars. For a better comparison of this region the PCA of the fingerprint region is more helpful.

4.3.2. Principal Component Analysis of the ATR FTIR Results In the methods and materials chapter it was explained under which conditions the PCA was done. The principal component analysis was done with 33 samples; samples 4 and 12 were excluded. Through the z-score standardization the ATR FTIR values were usable. Only the values of the fingerprint region 1500 – 500 mn-1 were taken into account, since the other regions of the spectra were close to identical. The Kaiser-Meyer-Olkin test verified that the variety was satisfactory, as the KMO = 0,9333 (“marvellous” according to Hutcheson and Sofroniou (1999) (Field, 2013, p. 685). The KMO values for the samples individually, expressed as the proportion of common variance within a variable also known as communalities, are all above 0,76. The expectable limit is 0.5 thus this is an acceptable results (Field, 2013). First an analysis was done to find the eigenvalue for the different components. From this three components with a value greater than kaiser’s criterion of the eigenvalue that is greater than 1 were found. These three components together explain around 94,6 % of the variance between the samples. The screeplot shows an acceptable curve of the three components. The rotated component matrix, Table 12, shows which samples cluster on the

same component. The rotated component matrix is visualized in a component plot that is shown in Figure 38.

Table 12 The rotated component matrix, a summary of principal component analysis results for the ATR FTIR fingerprint spectra (N=34) Components

Contemporary and Historic and solid Not pine species liquid Component 1 Component 2 Component 3

Sample 7 .961 -.040 .226

Sample 8 .822 .035 .283

Sample 9 .979 .049 .123

Sample 10 .972 .058 .044

Sample 11 .941 .021 .270

Sample 13 .976 .016 .019

Sample 14 .926 .029 .244

Sample 15 .940 -.037 .238

Sample 16 .978 .059 .101

Sample 17 .980 .020 .120

Sample 18 .991 -.013 .048

Sample 19 .963 .015 .218

Sample 20 .982 .023 .041

Sample 21 .972 .080 .148

Sample 22 .941 -.029 .182

Sample 23 .922 .013 .263

Sample 24 .979 -.007 .107

Sample 25 .981 .068 .035

Sample 26 .989 .035 .056

Sample 27 .953 -.031 .185

Sample 28 .361 .829 .183

Sample 29 .965 .006 .224

Sample 30 .956 -.046 .231

Sample 31 .988 .003 .122

Sample 32 .975 .005 .170

Sample 33 .965 .084 .190

Sample 34 .965 -.026 .171

Sample 1 -.004 .950 .000

Sample 2 -.014 .975 -.013

Sample 3 -.201 .930 .059

Sample 5 .237 .088 .956

Sample 6 .237 .089 .956

Sample 35 .836 .322 -.082

Eigenvalues 25,81 3,56 1,846

% of variance 78,2 10,8 5,6

Cronbach's 0,997 0,876 1 alpha

Figure 38 The components with the sample clusters. Component 1 represents that variance of the liquid and contemporary, component 2 represents the variance of the historic and solid, and component 3 represents the non-pine variance.

Reliability

A reliability analysis was done to determine the consistency of the measurement. For each cluster the Cronbach’s alpha was measured. For first component, liquid contemporary tars had a reliability alpha of 0.997, which all the samples that clustered on this component met. The second component, historic tars had a reliability alpha of 0.876. The samples 1,2,3, and 28 had a Cronbach’s alpha around the same value. The sample 35 however was far above this value and needed to be excluded from this cluster. The last component, the non-pine tars, had a reliability value of 1. Both tars sample 5 and 6 had the same Cronbach’s alpha value.

5. Discussion

5.1 Discussion of the results In this subchapter, the results of the TLC and ATR FTIR are related back to the hypotheses and questions that were put forward in the introduction.

5.1.1. Discussion of the TLC results In the introduction, a set of criteria was listed that determines if the TLC technique with the dichloromethane: hexane (2:3) (v/v) can be assessed as satisfactory. This list of criteria determines if TLC can categorise tars that are identical, similar, or different. This classification is done in the previous chapter by comparing the tar fingerprints. The tars were grouped beforehand, and each group was spotted out on individual plates. During the comparison in the last section, it became clear that taking only the location of the band into account was ambiguous for the bands in the lower part of the plate that were attached to each other. This made the consideration of the colour, radiance, and shape of the bands of more importance.

Is the TLC method successful?

The answer to the question if the TLC technique was successful in differentiating between the tars made from different source material, can be found in the analysis of plate B. Plate B showed tars from the sources coal, birch, and pine. The abietic acid was chosen as a standard for this plate, as this acid is primarily found in pine tars. Through the red reference line, it was stated that the coal tar does not have any bands at the same location as abietic acid. Besides the coal fingerprint does not show any overlap of bands with the other tars, for it does not show any band. The birch tar, on the other hand, has a fingerprint with bands, and the bands in the lower part did show overlap with the abietic acid reference line. As stated in the analysis based on the other aspects of the band it was identified as a different chemical compound. Overall the fingerprint of the birch tar seemed to have little in common with the pine tars.

The TLC method does show the difference between these tar species. In comparison with unknown tars, it is advised to use a standard to compare the tar too. In case this standard is not available, the fingerprints of this research can be used for reference. However, in that case, it is essential to use the same solvent system. The såide fractions showed that the difference in solvent systems also creates different fingerprints.

Through the analyses of the plates C and D it is possible to assess the compatibility of the TLC technique in identifying the production methods. The tars on plate C had fingerprints that could be classified into three groups: the traditional tars, the Claessons dalbränd fin tars,

and the trätjära tars. Between these prints was a significant difference. Within the three categories, there were similar band structures to group them. Plate D contained one industrial produced tar that was vastly different from the traditional tars. The customarily made tars from Gotland and Lapland had very similar fingerprints. This created on plate D a clear difference between industrial and traditionally produced.

Difference between the industrial tars

These two plates provide supporting evidence that the difference between industrial and traditional made tars can be identified through the means of this TLC technique. Between the industrial tars, there is a variation in the fingerprints. This is very apparent on plate C where various industrial produced tars are spotted alongside each other. The leading bands of the fintjara are the bands that correspond to the bands of abietic acid, the only other bands found in this fingerprint is one close at the solvent line. Whereas the dalbränd tars from Claessons and Biltema, which are categorised as trätjära, use the term trätjära that according to the RAA refers to sound quality tar. The fingerprints of these tars contain much more bands than the other industrial tars on plate C. This means that industrial tars can be distinguished from each other based on chemical properties. Alongside this, the quality of these tars can be determined through the comparison of a known high quality tar or with standards like abietic acid, dehydroabietic acid, and retene on the plate. The unknown tar based on the location of the bands the tar can be identified as high quality or not.

Difference between the traditional tars

For evaluating the variance between the customary tars, the logical choice is to focus on the analysis of plate D. All the customary tars on this plate were made on Gotland, except for the Arvidsjaur tar (numbered 26), which was created in Lapland. The fingerprints of the samples 20, 21, 22, and 26 are almost identical. The only aspect where these prints differ is in the shape of the bands. The traditionally produced sojdetjära (24) and Lokrume tar (25) both have an extra band in comparison to the other traditional tars. Thus there are some differences with the traditionally made tars, even though these tars were made on Gotland with assumingly the same Gotlandic custom. Through the distinct fingerprints, it makes it possible to identify a traditionally made tar from an industrially produced tar. As far as the information is known about these tars, the Gotlandic tars were all made in the same traditional way, burned in a såide. There is either a slight difference in the custom of this burning for the sojdetjära and Lokrume tar to have an extra band, or during the burning something happened that influenced the difference in the fingerprint.

Dalbränd

The ambiguous term dalbränd was discussed in the literature chapter of this thesis. To determine to what extent this term is connected to the quality of tar, the fingerprints of the TLC technique can illustrate the similarities and difference between the tars carrying this name and the traditional tars that were burned in a dal (såide, kiln). This research counted six tars that bore the name dalbränd and five tars of which it was known by the name they were made in a traditional kiln. Table 13 shows the tars alongside each other with their corresponding number of this research. Under Table 13, an image of the fingerprints stitched together is displayed.

Table 13 Dalbränd tars classified as dalbränd and burned in kiln. Carried the name dalbränd Burned in traditional kiln 10. Dalbränd from Gotland 20. Bunge museum tar

11. Dalbränd from Claessons 21. Arde tjära

13. Dalbränd from Claessons 22. Fardhemstjâra

15. Dalbränd from Claessons 24. Sojdetjära

17. Dalbränd fintjära from Claessons 25. Lokrume tjära

33. Dalbränd fintjära

Figure 40 The tars that were burned in a dal Figure 39 The dalbränd tars alongside each other

Figure 39 and Figure 40 show that the dalbränd tars do not have a foundation of band patterns that can be classified as dalbränd. There is apparently a difference in the chemical composition of the tars. The tars burned in a dal have a similar chemical composition. In comparison with the tars named dalbränd, there is a little resemblance. The results of the TLC plates provide evidence that supports the statement that the dalbränd term is not a guarantee of the quality of the tar.

Historical tars from the same structure

Most of the historic tars created unique fingerprints with the exception of two samples. The samples 17182 and 17189 on plate A have a very similar print. Through the visual and area analysis, there is a slight difference noticeable in the lower bands. The names of these tars are numbers that are close together in value. The numbers could refer to a shingle. The Scandinavian churches are often covered in shingles, and if these are taken off a number system could be used to keep count of them. This makes it seems very likely that these tar samples are from the same wooden structure.

Tars with special focus

The tars 1814 (32) and Dalbränd 1814 (33) were suspected to be from the same tar barrel that was found in a shipwreck. The two samples were spotted alongside each other on plate E. From the visual comparison and area analysis with the RGB colour theory the fingerprints were a match based on the same location of the bands, colour, and shape. There was a slight

tilt in of one of the samples on the image of the area analysis because the aligning was done manually. Through this conclusion, it can be stated that it is possible to identify tars that are identical with this solvent system.

Reject or accept hypothesis 1?

With these results hypothesis 1, the thin layer chromatography (TLC) method successfully identifies tars that are identical, similar, and different, can be accepted under the specific conditions. These conditions are that the solvent system that is used in this research needs to be used for it to give acceptable results. Other solvent systems were explored, but for these systems, a hypothesis was not tested. Through identifying if a tar is identical, similar, or different based on its chemical properties the quality of the unknown tars can be determined.

5.1.2. Discusssion of the ATR FTIR results The ATR FTIR method has, as the TLC method, a list of criteria that needs to be met for hypothesis 2 to be accepted. Hypothesis 2 states: “The Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR FTIR) method successfully identifies tars that are identical, similar, and different.” The acceptance of this determines if the method is to be considered successful in the identification of the tars. The criteria that needs to be met to assess the method are the following points:

1. The ATR FTIR needs to create spectra that show similar peaks for all the pine tars. These peaks can be used to determine if a tar is made of pine or not.

2. The ATR FTIR needs to produce a spectrum with similar peaks for all the different production methods. So the tars can be identified based on production method.

3. Finally, show a unique marker that can distinguish tars that are from the same source material and have the same production method but are not form the same geographical area.

Is the ATR FTIR method successful in showing the difference between tar species (coal, birch, softwoods)?

The first point of criteria states that the FTIR needs to create a different spectrum for the different tar species. In the case of this research those species were coal, birch, and pine. In the previous chapter the spectra of these tars were placed alongside each other in Graph 5. The graph shows that the spectrum of the pine tar was significantly different from the coal and birch tar, as it had peaks at different places and the pine tar missed the –OH slope of the dilution solvent of the coal and birch tar. The spectra of the coal and birch were identical. The ATR FTIR showed no differences between these two tars that are known be fundamentally different in composition (Mills & Whites, 1994, p.58-59). The identical spectra do show the sign of the same solvent present, ethanol. It is possible that the solvent and the cleaning

process influenced the outcome of the spectra. The two tars were analysed after each other. Overall the ATR FTIR was only partly successful as it was able to display a difference only between the pine tar and the other tars.

Does ATR FTIR technique show a significant difference between the tars with different production methods? Thus tars with similar production methods, do these have identical fingerprints?

The PCA results of the fingerprint region are used to assess the second point of criteria on the list. The spectra of the pine tars solid and liquid tars showed between 400 and 1500 nm-1 peaks at the same places. Therefore to distinguish these tars the fingerprint region of the tars were analysed in the PCA to determine which factors explained most of the variance between the tars. This variance is equal to what the tars are known to be different for. The PCA showed three components that explained more than 95% of the variance in all the pine tar samples. The variance components were: the liquid and contemporary, the solid and historic, and the different raw material.

PCA attempts

There were multiple attempted variations for the PCA. The initial idea was to use the complete spectra, however, this resulted in the PCA only finding on component of which the eigenvalue was larger than 1. Proofing that the complete spectra was able to show that all the tars were identified as tars with the ATR FTIR, but no other variance was strong enough to be noticed. Another attempt was to use on the fingerprint of the pine tars, to see if there was a difference noticeable between the pine tars, like production method. Also this attempt only showed one component above the eigenvalue 1. This component showed that the most variance of the samples was explained that these samples were pine tars. The last attempt was to use only liquid tars. This attempt showed two components above the eigenvalue 1: the first component being explained by the liquid pine, and the second by the non-pine material. These components were present in the overall PCA that was shown in the results section. The tars can be distinguished on two things the state of matter there in, thus in solid or in liquid form, and the tar species. It fails however, to show a significant difference based on the production method and the geographical area it was produced.

Reject or accept hypothesis 2?

The ATR FTIR did not meet the requirements for hypothesis 2 to be accepted. It was only limited in the identification of the tars. This result corresponds with the findings of Crawshaw (1997) that determined a similar conclusion for the use of infrared spectroscopy (IR). The ATR FTIR is able to identify the tars as similar and different based on the state of matter and

the tar species. For a more into depth research on quality comparison between tars and similarities based on chemical composition a different method needs to be used.

5.2. Evaluation This research aimed to explore different analysing techniques to distinguish tars from each other. The TLC technique has multiple ways of extracting information from the plate. These multiple ways were also explored. The results determine the evaluation of the methods and the ways of extracting information of the methods results.

5.2.1. Critical Reflection of the SEM EDX method The SEM EDX was only used to provide extra elementary information about the historic tars. The results were as expected. Most of the elements suggested the presence of sand, which was also found by visually examining the historical samples. There were originally more samples that were assessed with the SEM EDX. Unfortunately, the data of these samples were lost. One of the tar samples to which the results of the SEM EDX would have been beneficial was sample 28 rödtjara. This technique would have been helpful to identify the red pigment. The analyses of the tars that are included in the thesis have most of the analyses done at the magnification of 200. Some tars have the magnification at 500 or even at 100. Overall it does not affect the results of what elements are found, as the elements were easily connected to the substances found in the visual assessment. However, it would have been more appropriate to have a set magnification for all the sites of interest.

Samples of liquid tars were prepared to be analysed with the SEM EDX. Unfortunately, the results of these tars were not properly transmitted to a USB stick. This was only discovered after I had left Sweden. One of the tars that was analysed was the rödtjara, a red tar. This tar would have been interesting to have an elementary analysis of for the identification of the red pigment. It would have been more accurate to research all the tars with the SEM EDX, as one never knows what additives are present in the tar. Due to lack of time and the complicity of the machine only a selected number of tars were analysed.

5.2.2. Critical Reflection of the TLC Method Selecting the Method

This research studied the use of the TLC method with the same intention as the previous studies, and was therefore set up in a similar matter. In the preliminary studies of the TLC method other equipment was used to explore the possibility of lowering the costs of the technique. Specifically the Wood Tar project created the criteria for the TLC method to be: low cost, easy to use, and the possibility to use it anywhere. This criterion was also up held in this research. The Wood Tar project explored the use of chalk, nail polish remover, and iodine vapor. For this research a close version of a “recipe” used by Anthony Crawshaw was used, as

in his article it appeared to be quite effective and a working TLC method was aimed for. A small change was made in the recipe, since the original used chloroform. Due to the hazardous properties this was replaced with a slightly milder variant dichloromethane. Resulting in a TLC method set up that is similar to the previous studies but slightly different.

There are some complications with the way the TLC method was executed in this research. The TLC method is meant to be portable since the idea is that this can be done on site. One of the complications with this requirement is the solvent that is used within this research. The use of dichloromethane gives no other option but to run this analysis in a laboratory. The safety measures a strict for a solvent like dichloromethane. Other solvents can be used, in the Wood Tar project some of these solvents are explored. However, so far the organic solvents are most successful in solving tar. Even with an organic solvent that is not harmful to the executor’s health, there a flammable risk is still present. This would not be an issue, if it were not for the fact that the aim of this analytical method is to identify tar to re-tar historical wooden structures. These wooden structures should have no to very little contact with these substances. This issue can be solved by carrying out the experiment away from the wooden structure, or by to keep exploring solvents with a far less flammable risk. Either way the complications make the TLC method as it is presented in this research unlikely to be executed on site.

Another complication that makes the TLC method difficult to execute on site is the capturing of the fingerprints with a UV light. In this research a dark room was used with a multi spectral camera to capture these prints. Luckily through the Wood Tar project it is known that it is possible to capture the fingerprints also with an ordinary smartphone. The UV light and the dark room are a bit trickier, as the site most probably does not provides these two things. One can purchase a UV light in advance. The dark room does not have to be an entire room. A small well darkened box with a small gap through which the phone can snap a picture would work just as good. Thus even though this seems a bit tricky, it is the least difficult to solve on site.

Creating TLC plates

The tar samples were solved in dichloromethane. Before the final TLC plates were made, small changes to the developing process were made to perfect the procedure. These changes were made over a time course of weeks, and during those weeks the tar samples of which ±0,2 grams was solved in 2 mL of dichloromethane had the problem that the dichloromethane evaporated with some tars entirely and others only partially. To solve this problem, more dichloromethane was added to create the same solution. Unfortunately after every attempt, a little of the sample was taken for the development of the TLC plate. Thus there was not a

constant concentration. Luckily with TLC, this technique separates the chemicals, and the quantity of the tars sample does not have to be continuous for this method to work. For the såide fractions, the sample preparation was done on feeling, and the TLC plates still created a band pattern for all the samples. The såide fractions had a different purpose for this research, and the exact measuring for these samples was not deemed necessary.

Independent variables that had some problems in staying constant were: the angle of which the plate was placed in the development chamber, the amount of tar sample that was spotted, the place where the sample was spotted, and documenting of the TLC samples. The angle of the plate was difficult for each plate to be precisely the same, for the plates were placed in the developing chamber with tweezers. Due to the hazardous properties of dichloromethane, the placing of the plate had to be done quickly to limit the time that the chamber was open in the fume hood for safety reasons. The place and the amount of tar sample that was spotted differed in small proportions every time. The measures to make it as constant as possible were the use of the capillary tube to measure the amount of sample, and on the plate small squares were drawn were the sample was to be placed. For some samples, the place of spotting and the angle of the plate had a direct influence on the band pattern, as it during the developing started to tilt to the left. This tilted fingerprint created some difficulties in the interpretation of the area analysis with RGB stacks.

Plate E

Plate E is noticeably different from the other plates. This plate was created later than the other plates, and at that point in the research it was more interesting to spot the two possibly identical tars 1814 and Dalbränd 1814 alongside each other. To still have enough space on the plate for the other tar samples it was decided to not spot abietic acid on the plate. On the other plates abietic was present and created a stable fingerprint that appeared on the plates every time the same, and therefore it was less noteworthy to have abietic acid on the plate than the 1814 tars. Besides the spotted samples the multispectral image of this plate is completely different in comparison with the other plates. The Artist camera had to be built up after it was used on another project. The distance from the plate to the camera was not the same as for the other plates. Alongside this the calibration with for the UVF channel was done with a different fluorescing chart, since the chart used for the other plates had gone missing. This created different calibration settings for this plate, and explains why the appearance of the plate on the images shows the bands in a completely different colour.

Documenting the TLC plate with MSI

The TLC plates were documented through the use of multispectral imaging. With the use of UV light the bands became visible and thus was it important to capture the band patters in this specific light. The Artist camera was used to do so. The camera had to be set up a few times,

which made it impossible to have the camera in the same location. The consequences of this were the camera calibration different per photo session. This is very clearly visible on the TLC plates, as the bands of plate I-IV appear bluer, those of plate V brownish, and the photos of the såide burning more greenish. The images of made with the Artist camera are merely to show the band structures of the samples but should not be considered accurate on the colour scheme of the bands.

In hindsight this complication might have been solved through the use of a colour chart. Unfortunately at the time the use of a colour chart was not explained to me, and therefore the possibility it brings to adjust the colours of the images later on a Photoshop to have all the same colour levels was not done. This explanation of why a colour chart is useful was only provided after the first version of the thesis was written. If this experiment was done again this is one of the changes that would be made for more accurate results.

Colours of the TLC plates

The colours were measured with the Qmini spectrometer. These colours were measured in the CIE Lab colour system and the intention for these values was to create a PCA based on the colour per Rf. Unfortunately the statically explorations of using a PCA has led to the conclusion that is not possible to cluster the samples based on their measured colour and Rf. There were too many missing values as the Rf's that do not have a band area missing value in this system. Filling the missing values with the mean of the colour value of the non-luminous part of the TLC plate creates a PCA that shows the variance of the samples based on the number of nonluminous Rf ranges. Thus not based on the band colour value, which was the original intent.

RGB Stacks

The alignment of the sample's fingerprints for the RGB stack analysis was done manually. The concentration line was taken to align the images. Mentioned before was the spotting of the samples and the plate angle was done as constant as possible. Unfortunately, some samples' band patterns tilted more to one side. During the alignment, this was not corrected. Only for the comparison of the samples 32 and 33, and 31 with 34, this complication comes forward in the image. In the RGB stack for the samples 32 and 33, there is a slight tilt for the left for the red coloured sample. There is still a significant area where the two overlap, so the interpretation that the Rf values of the bands are always accurate. For the samples 31 and 34 it is the green sample that tilts a little to the right, but once again the bands have overlapping areas on which the interpretation is based.

5.2.3. Critical Reflection of the ATR FTIR method The decision to use the ATR FTIR method for this research was based on existing literature on the use of infrared spectroscopy for tar identification. The main source of this was the study done by Anthony Crawshaw. The ATR FTIR machine was available in the laboratory where the research was conducted, and made it therefore a possible option to explore. It is known that the analysis with this machine is done fast and efficient with direct results.

The execution of the ATR FTIR analysis is described in this paragraph. The ATR FTIR analyzed the tars in the state of matter of which they were donated to the research. This meant that in between the liquid tars the sensor needed thorough cleaning. The tars were placed on the sensor with a spatula. The cleaning of the sensor and the spatula was done in some cases with ethyl acetate, and in other cases with acetone. This cleaning process, even done with care, still left some residue. The reason for using the two cleaning solvents was to experiment which solvent cleaned the machine in the best way. Acetone solved the tar faster, but also evaporates much quicker. This cleaning process could have been done with more precision and with one cleaning solvent that was used constantly. It is possible that the cleaning process influenced the ATR FTIR results.

There were some complications with capturing the spectra of some of the samples. The historical samples that were still attached to wood were too large to fit entirely under the pressure applicator. Therefore smaller pieces were taken from these samples, with the consequence that the solid tar crumbled down and was hard to be equally spread out over the crystal surface. Alongside this, the coal sample was restricted to the fume hood for health reasons. The ATR FTIR was not located in the fume hood. Therefore the measurement of the coal and birch that followed this analysis was done rather quickly. The effect was that the machine was not thoroughly cleaned in between the measuring. This might be an explanation why these samples are so much alike. Another reason is the influence of the cleaning solvent, the same solution the tars were solved in, influenced the spectra.

Editing spectra

After the spectra were collected in the software OPUS, there were some difficulties with saving the data. The operating system of my laptop is OS X, whereas the computer with the OPUS software was a Windows. Not only was my computer unable to open the spectra that were collected. The Windows computer was only able to open the data within the OPUS program. Creating a PDF image of the capture spectra was possible. It was possible to open the spectra as numbers in excel. This way it could be transported to my laptop. During the export of the file's sample 4 got lost. This is the reason why this sample is not included in any

of the ATR FTIR results. This loss was only noticed when the laptop that was connected to the ATR FTIR had disappeared from the research laboratory.

The editing of the ATR FTIR results gave some difficulties. During the capturing of the spectra there was no normalization done. This was realized once it was no longer possible to alter the captured data in the OPUS program, as the computer with program was in a different country, a different solution was found for the standardization of the data. For this reason he z-score normalization was done manually, as it made the data usable for interpretation. This was the best solution that was possible from afar. However, the results would have been more reliable if the normalization as done right away with OPUS software. Especially so much time went over it, and the tars were measured at different moments it was hard to determine if all the spectra lacked the normalization or if some were normalized with the OPUS software. For the sake of the research all the data was treated equally, but there was lack of accuracy in the notes on this matter.

A peak selection is helpful for interpretation of the FTIR spectra. The OPUS software used to capture the spectra had an auto peak selection. Unfortunately, the peak selection of this software only selected one peak in the spectra of the tars, and it did not give a lot of added value or give information that was needed to test the hypothesis. The aim of this method was to show the difference between the different tars, based on the form of the spectra. Since only one peak got selected, it was not possible to do this comparison with the means of the peak selection. Therefore, the visual assessment was used as a means of interpretation for the graphs and in addition the PCA plot.

The things that would have been done differently in hindsight are the following: First, the liquid tars would be solidified on a glass plate, so all the tars are analyzed in the same state of matter. Second, the OPUS software would do a normalization right after the data is captured. And last, the PCA would be used again, for it has shown to be a very reliable technique to interpret the results. The only thing different there would be the use of all the values of the data and not just the fingerprint region. Changing these three points would make the ATR FTIR most probably more reliable and effective.

5.2.4. Other Complications An overall complication was the lack of information about the tar samples’ production method and place of production. The tar samples donated from the RAA came with little to no information. The information was written on a label, and based on the information provided at the conference in Östergarn some assumptions of the tars were made (private communications, 2017). These assumptions were mainly about the production method based on the provided geographical location. An example, on sample 24 the label stated “ sojdetjära

2009 (prov11)”. This term sojde or såide is the word for kiln in the Gotlandic dialect. Therefore it was assumed that this tar was made on Gotland in 2009. The “prov 11” in brackets refers to a test number. This numbering was done for the research of the RAA. From the word “prov” on the sample vessels no assumptions could be made about the tar, as it did not add any information.

5.3. Future Research The future research that is suggested in this section is stated for the continuation and improvement of the tar identification with chemical analytical techniques. Due to the lack of time and resources these option could not be explored during this research.

Different stationary and mobility phases TLC

A possible continuation of the TLC method is by improving this technique with various stationary and mobile phases. This would be improved by changing out the dichloromethane solvent system as this caused the bands to be close together. With the såide fractions in this research another solvent system was explored. The ratio of the solvent systems can be explored and have the possibility of clearer band structures, which would make the visual assessments of the plates easier and more reliable. Another aspect that might improve the band structures on the TLC plate is letting the plate develop in two dimensions. This way the bands spread more over the plate.

Use besides abietic acid also, dehydroabietic acid, retene, methyl dehydroabietate

In the case of using the TLC technique for the identification of the quality of tar, it is advised to use the following chemicals as a standard to determine the quality: abietic acid, dehydroabietic acid, retene, and methyl dehydroabietate. Even though this research only contained abietic acid, the other chemicals are linked to the quality of the tar as was stated in the literature chapter. For a complete knowledge of the chemical composition of each band the FT Raman spectrometer can be used. The original idea of this research was to analyse each band with a Direct Sample Analysis Time of Flight Mass Spectometer (DSA/TOF MS). This machine became unavailable during the course this research was executed, changing ultimately the course and outcome of this research. However, it is still advised to preform such a research in the future.

Exploration of tar with Scio spectrometer

The SCiO spectrometer is a relatively new piece of equipement (Consumer physics, 2017). It is a near infrared (NIR) micro-spectrometer that is used for analysing dry matter (Cargill.com,

2017). The SCiO is a portable spectrometer that shows direct results of the measured material on a tablet or phone. The SCiO spectrometer can be used in combination with the TLC plates. The spectrometer can measure each TLC band to create a map of fingerprints with the chemical properties of each band. This way the database of the prints has additional information on where the band is found on the plate and with which chemical composition it corresponds when there is no standard present on the plate. Another option is to explore the SCiO spectrometer to analyse the historic and the solidified form of the liquid tars and create a database with this technique. With this latter option it is possible to link the dried tars to the chemical composition of the liquid tar for a more optimal identification in the future.

6. Conclusion

In the introduction guidelines on the quality of tar were discussed as these were presented in the article Trätära: edömning a kvalitet of the RAA. The RAA ranked the tars that were made from the stumps and traditionally burned in a kiln as the best quality and whole trunk tars, which is only used in industrially produced tars, as lesser quality tars. Alongside this, the tar quality depends on the amount of abietic acid present (Riksantivarieämbetet, 2016). This research included a traditionally burned tar from Östergarn, Gotland. This tar was known to be of low quality due to the blow out that happened during the tar burning session. This tar is an example of a traditionally burned tar that still does not meet the requirements of high- quality tar. Tars like the Östergarn tar that lack the information about the tar burning session then need to be assessed on the amount of abietic acid present. This assessment was researched alongside the exploration to find a possible industrial tar with similar chemical properties as a traditionally burned tar. This study was done through the use of two analytical methods: TLC and ATR FTIR, to analyse tars.

The TLC method showed results that were most successful in fingerprinting the tars. The TLC method explained the difference between the tars that carried the name dalbränd and the tars that were burned in a “dal” (traditional kiln). Through the TLC fingerprints, the difference in chemical composition of the tars was shown. The tars burned in an actual “dal” all seemed alike, whereas the dalbränd named tars did not seem to have that many similar chemical properties. The method also showed that the chemical composition of the historic tars was very different from the liquid tars. These tars had diverse states of matter, as all the historic tars were solid and the other tars were all in liquid form. Even though it seemed expected it was good to explore the difference in fingerprint for these tars so it can be concluded that the solid and liquid tars should be analysed separate from each other and only compared with tars of the same state of matter.

Coal and birch tar showed a very limited fingerprint with the TLC method. The developing solvent was chosen based on the chemical composition of the pine tars. Therefore it is logical that the coal and birch tar band structure showed fewer bands since the developing solvent had less influence on the mobility of the chemicals in these two tars. For researching these tars with the TLC technique, a different developing solvent needs to be designed to optimise the possible bands. In this research is explained that it was not a pine tar through the lack of bands.

The TLC method was easy to interpret, although it has room for improvement. Besides being able to identify the tars as identical, similar, or different, three other requirements were part of this research. Analytical techniques needed to be low cost, easy to use, and field deployable. This way the tars can be analysed directly on site. The way the TLC method was performed

with dichloromethane makes it still hazardous to use outside a laboratory. However, in the Wood Tar Project, the TLC was run with development solvent of ethyl acetate, which showed promising results. Within this project different stationary phases were used. Instead of a silica layered glass plate, a piece of chalk was used. The different stationary and mobility phases make this method the most likeable to become field deployable. The various phases will also lower the costs of this experiment. The real high expenses are the purchase of a UV lamp, protective goggles, and the stationary phases. Once these investments are the method is low cost, easy to use, and field deployable. The results can be captured with any camera since the comparison of the bands can be made with an area analysis as this research has shown.

The ATR FTIR method had a lesser success than the TLC method. This technique had difficulty distinguishing the tars based on the production methods and the geographical production area. It was able to create different spectra for the tar species, coal, birch, and pine. Also, it was able to show the difference between historical solid tars and liquid tars. The fingerprint area of the spectra was not diverse enough to explain the difference between the different dalbränd tars, which through the TLC methods were known to have a different chemical composition. The only conclusion for the unknown tars was that these were pine tars. What a researcher can learn without using an ATR FTIR.

The reason why the ATR FTIR is not very satisfactory, besides not meeting the requirements on distinguishing the tars, is also that it is not useable outside a laboratory and low cost. The ATR FTIR is still laboratory bound, as it needs electricity and a laptop. One of the advantages of the methods was that it is not difficult to use. The OPUS software is straightforward to use and explains precisely the steps of collecting the spectrum. Within seconds the spectra can be obtained and exported to a different program, such as excel. Another advantage is that the historic tars were not solved before analysed. All the tars were examined in their pure form. Even with these benefits this technique hardly has any possibilities to explore for improving tar identification besides the ones studied in this research and previous research.

In conclusion, this research puts forward one useful method for the identification of tar. The thesis has explored the possibility of two methods to assess the quality of tar based on its chemical properties, of which the TLC technique came out as satisfactory. The method TLC met most of the requirements for the technique to be seen as successful. It showed potential for the study of finding an industrial pine tar with similar chemical properties as a traditionally burned tar. Some fingerprints of the industrial and traditional tars bear a resemblance to each other. For a better assessment tars need to be spotted on the same plate. The other method, the ATR FTR, only met a few points of the criteria list and is therefore considered not the best technique for this study. For the additives analysis, it is advised first to do a visual assessment for the low cost, simple use and in field usage. In the case of need the SEM EDX can be used to determine the elements of additives in the tars.

7. Executive Summary

This thesis reports on the comparative study of analytical methods that can be used for tar identification. This research explores the possibility to find an industrially produced tar with similar chemical properties as the traditionally produced tar. The general view is that the traditionally produced tar is of a higher quality, based on its abundance of the abietine group that is present. During this research, two chemical analytical methods are assessed on the usability of tar identification. For the technique to be considered successful, it needs to meet a set of criteria. First of all the method needs to identify tars that are identical, similar, and different. Second, the technique requires allowing for an into depth chemical comparison between the tars. The last set of criteria is that it needs to be usable in a noncomplex way, field deployable, and be low cost. The two methods that were chosen based on these criteria in mind were: thin layer chromatography (TLC) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR). In addition to these two methods, the Scanning Electron Microscope-energy Dispersive X-ray (SEM EDX) was used to research additives that were possibly present in the solid tar samples.

The research contained 34 different tars. Of the 34 there were five samples historical tar samples in their solid phase, the other samples were all in liquid phase. The research contained one coal tar and one birch tar sample. The different samples were either pine tar or the source was unknown. The standard that was used for the TLC method was abietic acid, a chemical primarily found in pine tars. The historical samples for the SEM EDX were carbon coated. No preparation was needed for the samples for the ATR FTIR analysis. The tar samples for the TLC method were solved in dichloromethane. These samples were developed with the developing solvent dichloromethane: hexane (2:3) ratio by volume.

In addition to the 34 tar samples, an additional analysis was done with the TLC technique on a traditionally burned pine tar that was burned in såide, Gotlandic for kiln, at Östergarn May 2017. This pine tar was studied separately from the other tars. During the burning, the tar was captured in fractions. The seven fractions were kept separate and spotted alongside each other on a TLC plate. This extra analysis was done with the aim to investigate if TLC shows a different fingerprint for each fraction. The fractions had a series solved with dichloromethane and ethyl acetate. The fractions solved in dichloromethane were developed in the dichloromethane: hexane (2:3) ratio by volume and the ethyl acetate solved fractions were prepared in the developing solvent ethyl acetate: hexane (1:50) ratio by volume.

The fingerprints of the tar samples on the TLC plates were visible in ultraviolet (UV) light 366 nm-1. A comparative visual assessment was done. The plates were photographed with the Artist multispectral imaging camera in ultraviolet fluorescence (UVF). The images were used to measure the Rf of each band in Autodesk. With fluorescence spectroscopy, the colour of

each band was measured in (UV) light 366 nm-1. A comparison of the band areas on the plates was made with ImageJ.

The TLC method was successful in distinguishing the tar source material in the following categories: coal, hardwood birch, and softwood pine with the tree species Pinus Sylvestris. The following classifications were made based on the TLC results about the production method: industrial method, modern kiln, and traditionally burned. There was also a correlation between the traditionally burned tars from Gotland. The ATR FTIR method was able to distinguish the tars on the source materials: coal, hardwood birch, and softwood pine. This was visible in the spectra. Through the principal component analysis (PCA) it became clear that only the following components explained the variance between the tars: component 1 the liquid phase, component 2 the solid phase and thus historical, and component 3 the tar’s raw material. The ATR FTIR failed to give a fingerprint for each tar that has a peak that can be used as an identifier. The liquid pine tars were too similar to notice a significant difference.

In conclusion, the TLC method was most successful in identifying tars based on their chemical properties. The ATR FTIR method was most comfortable to use and got the fastest results. For a more into depth knowledge, the TLC method appeared to be most successful. TLC is the cheapest method and the one most likely to be taken outside the laboratory. The SEM EDX was successful in identifying the additives, but overall it did not add useful information in identifying tars. The TLC method as it was executed in this research is not field-deployable, due to the dichloromethane in the solvent system. Previous research shows there is a possibility to use a different mobile phase and making it not only cheaper as well as field-deployable.

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8. References

8.1. Non-printed Sources

Nordic Tar Network. (2017). Tjära. Presentation, Katthammarsvik, Gotland.

Östergarn såide burning notes and observations. (2017). Östergarn.

Syversin,, M. (2017). Traditional tar burning process. Östergarn.

8.2. Printed Literature

Åbruhammar, T. (2016). Method for thermal treatment of raw materials comprising lignocellulose. Sweden.

Aftalion, F. (2001). A history of the international chemical industry (2nd ed., pp. 102-195). Philadelphia: Chemical Heritage Press.

Berg, B., & McClaugherty, C. (2014). Plant Litter: Decomposition, Humus Formation, Carbon Sequestration (p. 23). Heidelberg: Springer Berlin Heidelberg.

Bergen, K., & Thomas, J. (2017). Low Cost Tar Analysis: a citizen science approach. In SEAHA. Brighton: SEAHA.

Bos, R., & Jongeneelen, F. (2017). Nonselective and selective methods for biological monitoring of exposure to coal-tar products. In H. Bartsch, K. Hemming & I. O’Neill, Methods for Detecting DNA Damaging Agents in Humans: Applications in Cancer Epi- demonology and Prevention (89th ed., pp. 389–395). Lyon, France: IARC Scientific Publications.

Budavari, S. (1998). The Merck Index, an encyclopedia of chemical drug, and biologicals. Merck, 540.016(B927).

Colombini, M., Giachi, G., Modugno, F., Pallecchi, P., & Ribechini, E. (2003). THE CHARACTERIZATION OF PAINTS AND WATERPROOFING MATERIALS FROM THE SHIPWRECKS FOUND AT THE ARCHAEOLOGICAL SITE OF THE ETRUSCAN AND ROMAN HARBOUR OF PISA (ITALY)*. Archaeometry, 45(4), 659-674. http://dx.doi.org/10.1046/j.1475-4754.2003.00135.x

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Connan, J., & Nissenbaum, A. (2003). Conifer tar on the keel and hull planking of the Ma'agan Mikhael Ship (Israel, 5th century BC): identification and comparison with natural products and artefacts employed in boat construction. Journal Of Archaeological Science, 30(6), 709-719. http://dx.doi.org/10.1016/s0305-4403(02)00243-1

Crawshaw, A. (1997). Low Technology Analyses of Tars and Pitches. In The First International Symposium on Wood Tar and Pitch (pp. 197-202). Warsaw: State Archaeological Museum.

Egenberg, I. (2003). Tarring Maintenance of Norwegian Medieval Stave Churches (Ph.D). University of Gothenburg.

Egenberg, I., & Glastrup, J. (1999). Composition of kiln-produced tar. ICOM Committee For Conservation, 2, 862-867.

Egenberg, I., Aasen, J., Holtekjølen, A., & Lundanes, E. (2002). Characterisation of traditionally kiln produced pine tar by gas chromatography-mass spectrometry. Journal Of Analytical And Applied Pyrolysis, 62(1), 143-155. http://dx.doi.org/10.1016/s0165- 2370(01)00112-7

Egenberg, I., Holtekjølen, A., & Lundanes, E. (2003). Characterisation of naturally and artificially weathered pine tar coatings by visual assessment and gas chromatography- mass spectrometry. Journal Of Cultural Heritage, 4(3), 221-241. http://dx.doi.org/10.1016/s1296-2074(03)00048-7

Evershed, R., Jerman, K., & Eglinton, G. (1985). Pine wood origin for pitch from the Mary Rose. Nature, 314(6011), 528-530. http://dx.doi.org/10.1038/314528a0

Field, A. (2012). Discovering statistics using SPSS (and sex and drugs and rock 'n' roll). Los Angeles [Calif.]: SAGE.

Font, J., Salvadó, N., Butí, S., & Enrich, J. (2007). Fourier transform infrared spectroscopy as a suitable technique in the study of the materials used in waterproofing of archaeological amphorae. Analytica Chimica Acta, 598(1), 119-127. http://dx.doi.org/10.1016/j.aca.2007.07.021

Gosselin, R., Smith, R., & Hodge, H. (1984). Clinical toxicology of commercial products. Baltimore: Williams & Wilkins.

Hayek, E., Krenmayr, P., Lohninger, H., Jordis, U., Moche, W., & Sauter, F. (1990). Identification of archaeological and recent wood tar pitches using gas chromatography/mass spectrometry and pattern recognition. Analytical Chemistry, 62(18), 2038-2043. http://dx.doi.org/10.1021/ac00217a026

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Hill, B., Roger, T., & Vorhagen, F. (1997). Comparative analysis of the quantization of color spaces on the basis of the CIELAB color-difference formula. ACM Transactions On Graphics, 16(2), 109-154. http://dx.doi.org/10.1145/248210.248212

Hjulström, B., Isaksson, S., & Hennius, A. (2006). Organic Geochemical Evidence for Pine Tar Production in Middle Eastern Sweden During the Roman Iron Age. Journal Of Archaeological Science, 33(2), 283-294. http://dx.doi.org/10.1016/j.jas.2005.06.017

Krasutsky, P. (2007). Birch Bark Research and Development. Cheminform, 38(17). http://dx.doi.org/10.1002/chin.200717262

Kurt, Y., & Isik, K. (2012). Comparison of Tar Produced by Traditional and Laboratory Methods. Studies On Ethno-Medicine, 6(2), 77-83.

Kurt, Y., Suleyman Kaçar, M., & Isik, K. (2008). Traditional Tar Production from Cedrus libani A. Rich on the Taurus Mountains in Southern Turkey. Economic Botany, 62(4), 615-620. http://dx.doi.org/10.1007/s12231-008-9023-x

Levell, N., & Peters, T. (2011). Care and punishment: a history of coal tar and wood tar in dermatology. In 91st Annual Meeting of the British-Association-of-the- Dermatologists (p. Poster). London: Norfolk and Norwich University Hospitals. Retrieved from http://www.bad.org.uk/shared/get- file.ashx?itemtype=document&id=1398

Mills, J., & White, R. (2002). The organic chemistry of museum objects. Hoboken: Taylor and Francis.

Regert, M., Alexandre, V., Thomas, N., & Lattuati-Derieux, A. (2006). Molecular characterisation of birch bark tar by headspace solid-phase microextraction gas chromatography–mass spectrometry: A new way for identifying archaeological glues. Journal Of Chromatography A, 1101(1-2), 245-253. http://dx.doi.org/10.1016/j.chroma.2005.09.070

Reunanen, M., Ekaman, R., & Hafizoglu, H. (1996). Composition of Tars from Softwoods and Birch. Holzforschung, 50(2), 118-120.

Ribechini, E., Bacchiocchi, M., Deviese, T., & Colombini, M. (2011). Analytical pyrolysis with in situ thermally assisted derivatisation, Py(HMDS)-GC/MS, for the chemical characterization of archaeological birch bark tar. Journal Of Analytical And Applied Pyrolysis, 91(1), 219-223. http://dx.doi.org/10.1016/j.jaap.2011.02.011

Rosin/Colophony. (2017). Oxford Dictionary of English.

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Stuart, B. (2007). Analytical techniques in materials conservation. Chichester, England: John Wiley & Sons.

Tar. (2017). Oxford Dictionary of English.

Torsten, A. (1923). Nägra tjärbränningsmetoder i västra Sverige. Fataburen.

U.S. Department of Health and Human Services Public Health Service. (1995). Toxicological Profile for Polycyclic Aromatic Hydrocarbons. Washington D.C.: Agency for Toxic Substances and Disease Registry.

8.3. Electronic Sources

Aveling, E., & Heron, C. (1998). Identification of Birch Bark Tar at the Mesolithic Site of Star Carr. The Harwood Academic Publisher Imprint. Retrieved from https://www.researchgate.net/publication/247936420_Identification_of_Birch_Bark_Tar _at_the_Mesolithic_Site_of_Star_Carr

Baumgartner, A., Sampol-Lopez, M., Cemeli, E., Schmid, T., Evans, A., Donahue, R., & Anderson, D. (2012). Genotoxicity Assessment of Birch-Bark Tar—A Most Versatile Prehistoric Adhesive. Advances In Anthropology, 02(02), 49-56. http://dx.doi.org/10.4236/aa.2012.22006

Boreal Forests of the World - FINLAND - FORESTS AND FORESTRY. (2017). Borealforest.org. Retrieved 9 October 2017, from http://www.borealforest.org/world/world_finland.htm

Bungemuseet AB. (2017). Efter lite tråkiga nyheter försöker vi istället fokusera på bättre! Efter en fantastiskt trevlig kväll igår då vi tände sojdet har det nu börjat sippra ut tjära. Ta chansen och se det på plats i några dagar till. Häftigt. Retrieved from https://www.facebook.com/bungemuseet/videos/916892751782096/

Chemical Substances Bureau. (2003). COAL TAR PITCH, HIGH TEMPERATURE. Bilthoven: European Communities. Retrieved from https://echa.europa.eu/documents/10162/13630/trd_rar_hh_netherlands_pitch_en.pdf/2ba 26f8a-97d3-436d-81d5-307ee0ad3f61

CNRS Chemical Risk Prevention Unit (PRC). (2009). CARCINOGENS, MUTAGENS, REPRODUCTIVE TOXICANTS. Paris: The National Center for Scientific Research. Retrieved from http://www.prc.cnrs.fr/IMG/pdf/cmr-criteria-clp.pdf

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Deeshka Tab Destructive distillation of coal. (2013). YouTube. Retrieved 11 April 2017, from https://www.youtube.com/watch?v=P1ebNgtUwAo

Field, A. (2013). Factor Analysis/PCA. https://www.youtube.com/watch?v=UWP9OEoaNnE&t=663s.

Fossum, M., & Hustad, J. (2013). Biomass gasification for industrial production of tar and charcoal. In A. Bridgwater, Advances in Thermochemical Biomass Conversion (pp. 1242-1256). Springer Science & Business Media. Retrieved from https://books.google.nl/books?id=ji3pCAAAQBAJ&pg=PA1243&lpg=PA1243&dq=pro totype+plant+trondheim+norway&source=bl&ots=P9tOUZou3q&sig=RtQLtxrM0_JcC KVOrLMeYTm7qUs&hl=en&sa=X&ved=0ahUKEwjFjs7xo8_WAhWHXBoKHb0FBjI Q6AEIPDAF#v=onepage&q=prototype%20plant%20trondheim%20norway&f=false

Marchand-Geneste, N., & Carpy, A. (2003). Theoretical study of the thermal degradation pathways of abietane skeleton diterpenoids: aromatization to retene. Journal Of Molecular Structure: THEOCHEM, 635(1-3), 55-82. http://dx.doi.org/10.1016/s0166- 1280(03)00401-9

Mendeleyev, D., & Pope, T. (1969). The principles of chemistry. New York: Kraus Reprint Co.

Reveal Forage Analysis | Cargill. (2017). Cargill.com. Retrieved 9 November 2017, from https://www.cargill.com/animal-nutrition/innovation/reveal-forage-analysis

RÖDTJÄRA. (2017). Claessons.com. Retrieved 13 October 2017, from https://claessons.com/internetbutik/tratjaror/rodtjara

Sarifuddin, M., & Missaoui, R. (2005). A new perceptually uniform color space with associated color similarity measure for content-based image and video retrieval. In ACM SIGIR 2005 workshop on multimedia information retrieval (MMIR). Quebec , Canada: Research Gate. Retrieved from https://www.researchgate.net/profile/Sarifuddin_Madenda/publication/228906385_A_ne w_perceptually_uniform_color_space_with_associated_color_similarity_measure_for_c ontent-based_image_and_video_retrieval/links/562a20a308ae04c2aeb1551a.pdf

SCiO - The World's First Pocket Sized Molecular Sensor. (2017). Consumer Physics. Retrieved 9 November 2017, from https://www.consumerphysics.com/

Shenet - Tjära och tjärolja. (2017). Shenet.se. Retrieved 1 October 2017, from http://www.shenet.se/ravaror/tjara.html

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Swedish Primary Timber Trees | Nordic Timber. (2017). Nordictimber.org. Retrieved 9 October 2017, from https://www.nordictimber.org/sweden-primary-timber-trees

8.4. Figures

Figure 1 Flow of coal tar productions and by-products of the process. Derived from Agency for Toxic Substances and Disease Registry, 2002, p. 18.

Agency for Toxic Substances and Disease Registry. (2002). https://www.atsdr.cdc.gov/toxprofiles/tp85.pdf (p. 18). Washington D.C.: U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES. Retrieved from https://www.atsdr.cdc.gov/toxprofiles/tp85.pdf

Figure 4 Different traditional tar kilns with different drainage systems drawing from Farbregd 1989 p.10-11 (Egenberg, 2003, p. 2006)

Farbregd, O. (1989). Variety of technical devices for Pine tar production in Norway. In I.M. Egenberg "Tarring Maintenance of Norwegian Medieval Stave Churches" (2003) in Print, p. 62.

Figure 5 The construction of the kiln of Egenberg's research. "The FNN96 pile of wood under construction, like a three-dimensional puzzle" (Egenberg, 2003, p. 85)

Egenberg, I. M. (2003). Tarring Maintenance of Norwegian Medieval Stave Churches (Ph.D). University of Gothenburg, p. 85.

Figure 7 Vintage retort with condensation tube that is cooled by water (Mendeleyev, 1897)

Mendeleyev, D., Lawson, T., & Kamensky, G. (2016). Distillation from a glass retort. The neck of the retort fits into the inner tube of the Liebig's condenser. The space between the inner and outer tube of the condenser is filled with cold water, which enters by the tube g and flows out at f.. Retrieved from https://www.gutenberg.org/files/51326/51326- h/51326-h.htm

Figure 8 Isoprene structure (Wikipedia "Isoprene Structure", 2005)

Wikipedia. (2005). Isoprene Structure. Retrieved from https://en.wikipedia.org/wiki/Isoprene#/media/File:Isoprene-Structure.png

Figure 9 Reactions during a tar burning process. Abietic acid undergoes dehydrogenation and isomerization of the double bonds that forms dehydroabietatic acid. This acid is followed

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by carboxylation, the carboxyl is present through the presences of methanol, and this creates methyl dehydroabietate (Hjulström et al., 2006, p. 284).

107 Tjära på Gotland Januari – december -2017 På jakt efter ny kunskap och gotländsk tjärtradition Maj – december- 2018

Förra året -2017

- Arkiv sökning i gamla kyrkböcker

- Fältundersökningar med tjärprover från ex. Garde kyrka, Vall kyrka mfl.

- Vilken kunskap finns i muntlig tradition? Möten med såidesbrännande hembygdsföreningar. I samarbete med Gotlands Hembygdsförbund.

- Samarbete kring temperaturmätning i Sojdesbränning i Ardre 1930-tal. såide med Östergarns - Gammelgarns Foto Johan Klintberg. Hembygdsförening Sande såjde

Tjärbränning i Östergarn med seminarium för Nordic Tar Network

Tjärbränning är en åter- kommande verksamhet i många hembygdsföreningars regi.

Trevlig folkfest, ca. 14 såiden (tjärdalar) bränns regelbundet, men inte varje år.

Tjäran förbrukas lokalt.

Ardre Såjde

Mätresultat Ardre Mätresultat Sande såjde 36 22 hinkar hinkar

Sista hinken 103 Tjäran börjar rinna Efter 93 hinkar avtog flödet

Tjäran börjar rinna 1 hink / 30 min

Temperaturmedelvärde över tid för Sande och Ardre såjde och mätvärden från Norge

Ardre FNN 96 Skjåk Sande

Nordreisa

Åsnes

Tjära i förhållande till ved och brinntid

Sojde Staplad ved i kbm L tjära totalt L tjära /kbm Brinntid h

Sande 9 400 44 42

Ardre 10 700 70 64,5

Skjåk 34 1200 35 40

Nordreisa 8 300 37.5 44

FNN 96 (Øverbygd) 35 1050 30 31

Åsnes 9 200 22 45 Resultatet i sin helhet indikerar att det gotländska furuvirket utmärker sig som Resultatet visar också att ett virke med högre densitet jämfört med furuvirke från andra delar av Sverige, förekomsten av höga halter samt att den uppenbarliga tillgången på gamla träd med hög kärnvedandel extraktivämnen inte kan korreleras erbjuder bra möjligheter för utvinning av virke med hög andel kärnved eller till bonitet men att det kan finnas virke bestående av 100 % kärnved. områden där sådana träd kan hittas på. Temperaturmedelvärde över tid för Sande och Ardre såjde och mätvärden från Norge

Ardre FNN 96 Skjåk Sande

Nordreisa

Åsnes

Tjära i förhållande till ved och brinntid Nytt projekt från maj 2018

Projektstart: 1 maj 2018 Avslut : 31 december 2018 I samarbete med Visby stift, egendomsnämnden och samfälligheten Gotlands kyrkor.

Syfte: - Öka kvalitén på den gotländska tjäran gällande metoder för bränning och applicering.

Delmål: - Utveckla appliceringsmetoder tillsammans med tjärsmörjare

- Hitta metoder för bättre råvaruförsörjningen till tjärbränning.

- Undersöka retort (ungsbränning) som industriell teknik för framställning av lågbränt tjära.

- Tillgängligöra kunskaper om tjära genom permanent informationstavla på Kulturreservatet Norrbys.

- Fortsätta nätverksarbetet mot såjdeslag skogsfolk och tjärbrännare samt Nordic tar Network. Katning /randbarkning (slinnebarking) av skog

I samarbete med ALMI Fetvedens Vänner och AB Gotlänskt Kärnvirke

Reflektioner

- Det finns flera olika uppgifter om hur mycket tjära som använts.

- Vi har sett ett mönster i att man tjärsmorde i intervaller om 4-5 år och att man sedan hade uppehåll på 10 -15 år.

- Möjligen kan man också i räkenskaperna få reda på när på året man smörjde taken.

- Vi har inte sett någon form av förtjockningsmedel som kol eller sand. Vare sig som inköp i räkenskapsböckerna eller vid fältstudierna. Det har förkommit att man blandat i kimrök och rödfärg.

- De branta taken, i synnerhet på tornen borde ha krävt någon Utdrag ur Rone kyrkas form av förtjockning. räkenskaper 1766 Taket på Rone kyrka

Ex.Rone kyrka: 1766 köptes det in drygt 7 tunnor till tornets strykning.

Om man räknar med en tunnvolym på 125 liter blir det nästan 2 liter per kvadratmeter. Vilket borde ge en filmtjocklek på nästan 2 mm.

Vid flera tjärsmörjningstillfällen har man hyrt en gryta för att koka tjäran. Tjärsmorning i dag

Gotländska kyrktak får i genomsnitt en strykning med tjära vart 6:e år. Några ex:

Tofta ka: ca 824 m2 / 380 l = 0,46 l/m2 När ka: ca. 1285 m2 / 550 l = 0,42 l/m2 Eskelhem ka: ca.1092 m2/ 500l = 0,5 l/m2

Med andra ord ligger man på en knapp halvliter per kvadratmeter i medeltal när man tjärstryker kyrktaken idag. (I siffrorna ingår också strykning av portar och trävirke i fasad. ca 10-20 l per kyrka. ) Recept med inblandning av kol, kimrök och sand har hämtats från renoveringen av tiondeboden i Ingatorp, Småland , Sverige och Kvikne kyrka, Hedemark, Norge Grundläggande tjärblandningar

• Orginalrecept 1790 Orginalrecept för tjärsmörjning av tak för Kvikne kyrka i Norge. • Kungliga vetenskaps- akademien Forbruk ca 0,8 liter kull og 1,3 • liter tjære/m² takflate. • Ca 10 liter tjära från Hjärtasjön 2014 Halvparten av kullet skal blandes • 5 liter kimrök wibo inn før tjærebreing mens den • 1 liter krossat kol från siste halvparten kan benyttes til kolmila Ingatorp påkasting. • 0,5 liter brun umbra Kull blandes inn ett døgn i • 200 gram hartz. forkant av bruk i forholdet 2:5 Kull/tjære (ca 2 liter kull pr 5 liter tjære).

Oppvarming til 60 grader før tjurrubreing, Kaste på kull, ca 0,4 liter pr m². . Kaste på sand, ca 0,4 liter/m² Koka beck 180 – 200° i 30 minuter Reflektioner

- Det finns uppgifter som tyder på att man kokat tjäran till beck. men det är svårt att utläsa om syftet med grytan är för att becka tjäran eller för att endast värma den.

- Fraktionsuppdelning har säkerligen förekommit eftersom man tidigt ger den första fraktionen namn som jungfrutjäran, blomman mm. och tillskriver de olika tjärtyperna olika egenskaper.

- Att tappa upp tjäran på mindre trätunnor gav också en naturlig uppdelning. Förmodligen så självklart att ingen brydde sig om att skriva ned vikten av fraktionsuppdelning.

1. 2.a. 2.b 3. Befintlig gotländsk metod. Serbisk Inkokt Inkokt dalbränd tjära, Serbisk Furutjära-A ströks vid 45 °. Dalbränd Retortbränd tjära rollat på gammalt trä 1. Bägge värmdes till 145° i Befintlig gotländsk metod. Serbisk dalbränd tjära, 10 min och ströks vid 55° ströks vid 45 °. Orginalrecept 1790 Kunliga vetenskaps-akademien. 2.l. gotländsk såjdesbränd tjära Blandad med 2dl kol + 1 dl kimrök Ströks vid 55° 4. 5.

Orginalrecept 1790

Kungliga vetenskaps-akademien.

2. l. gotländskOrginalrecept såjdesbränd tjära 1790 blandad medKungliga 1 dl kimrök. vetenskaps-akademien. Recept för Kvikne kyrka i Norge.

Ströks vid 55° 2. l. gotländsk såjdesbränd tjära 2. l. gotländsk dalbränd tjära blandad med 1 dl kimrök. Blandat med 4 dl kol, ströks vid 55° 4 dl kol och 4 dl sand påkastat Ströks vid 55° efter strykning. . 6. 7.

2. l. inkokt Gotländsk såjdesbränd tjära.

145° i 10 min.

Recept för Kvikne kyrka i Norge, Uppblandad2. l. medinkokt järnoxidrött Gotländsk dalbränd 1-2 delar till 8 delar tjära men utan sand. tjära, 145° i 10 min.

Ströks vid 55° 2. l. gotländsk såjdesbränd tjära Uppblandad med järnoxidrött Blandat med 4 dl kol 1-2 delar till 8 delar tjära + 4 dl kol påkastat efter strykning.

Ströks vid 55° Ströks vid 55° 8. 9.a 9.b

Serbisk Gotländsk Recept för Kvikne kyrka i Norge dalbränd dalbränd med inkokad gotländsk tjära tjära inkokt dalbränd tjära, 145° i 10 Recept för Kvikne kyrka i Norge inkokt till till 145° i minuter. med inkokad gotländsk 145° 10 min. dalbränd tjära, 145° i 10 minuter. i 10 min. 2. l. gotländsk såjdesbränd tjära Rollat på nytt trä Blandat2. l. gotländsk med 4 såjdesbränddl kol tjära +Blandat 4 dl kol med och 44 dldl kolsand + 4 dl kol Bägge ströks vid S påkastatoch 4 dl eftersand påkastatstrykning. efter strykning. 55° 55° 10. 11.

Beckad gotländsk dalbränd tjära Uppvärmd till 200 ° i 30 minuter. Ströks vid 60° Furutjära A. inkokt till 145° i 10 minuter. Ströks vid 55° Kommentarer från Tjärsmörjare Johan Byh

Alla blandningar var strykbara med roller. Även de med inblandad kol. Den beckade ytan rollades också utan större svårigheter, även om den var segare att arbeta med. Denna blandning skulle kanske kunna sprutas vid 70°? Påkastning av kol eller sand kändes svårt utifrån de förutsättningar vi arbetar med på kyrktaken, då vi ofta arbetar från sky-lift med liten plats och dessutom är ganska vindutsatta. Att stryka på inkokt tjära med inblandning av kol med roller var däremot inget problem. Tilgang på og bruk av milebrent tjære på stavkirker

Nordic Tar Network, Tønsberg 09.10.2018

Merete Winness Leder museum og eiendom

Inger Marie Egenberg snakket om tjære i går

Ola Fjeldheim snakket om Tjærebanken i Uppsala i 2016

Jeg skal ikke snakke om kjennetegn for milebrent tjære, innkoking og påføring, slik at jeg ikke gjentar for mye av det dere allerede har hørt og lest

Jeg vil heller gi en kortfattet historikk for samarbeidet om å samle kunnskap om kvalitet og bruk og for å opprettholde tradisjonen og produksjon av milebrent tjære i Norge. Dette fordi jeg mener at man gjensidig deling av kunnskap og erfaringer mellom produsenter, brukere og forvaltere er nødvendig ikke bare for å få gode resultater, men også for å videreføre tradisjonen med milebrenning.

1 1980-tallet Tradisjonen med å produsere tjære i miler var nesten borte i Norge. Steinkulltjære var vanlig i bruk på fredete bygg, inklusive stavkirke.

1990-tallet Bevisstheten rundt materialbruk økte, dels på grunn av bevissthet rundt skader, dels på grunn av økt fokus på tradisjon og miljø.

Riksantikvaren krever at det skal brukes milebrent tjære på stavkirkene, fordi man mener at de opprinnelig ble tjærebredd og fordi man ønsker … å bruke tradisjonelle materialer og håndverksmetoder ved restaurering, istandsetting og vedlikehold. Da fremmer man samtidig bevaringen av håndverket og av den tradisjonelle materialforståelsen.

(Riksantikvarens informasjonsark 3.9.12, 2002) 2

… Av de 28 stavkirkene våre fra middelalderen (1050-1537) som er bevart, tjærebres fortsatt 23, helt eller delvis. (NINA-NIKU faktatark nr 14 – 2001)

… Men siden skulle Bønderne tiære Deres Kirke hver 3 vinter (Magnus Lagabøters Gulatingsliv, nevnt i Riksantikvarens informasjonsark 3.9.11 sist oppdatert i 2005.

2 1990-tallet Riksantikvaren, Norsk institutt for kulturminneforskning (NIKU) og Fortidsminneforeningen samarbeidet om å samle kunnskap om kvalitet og bruk.

Tjærebanken ble opprettet for å sikre tilgangen på milebrent tjære, og for å gi produsentene mulighet for avsetning. Tjærebanken drives av Fortidsminneforeningen som tar i mot og selger milebrent tjære.

3 1993 Godkjenningsnorm for milebrent tjære (Egenberg, 1993)

1993 Produksjonsskjema

1993 Rapporteringsskjema for tjærebreing

1994 Riksantikvarens informasjonsblad om produksjon av tjære

1994 Riksantikvarens informasjonsblad om tjærebreing

1993 På grunnlag av undersøkelser i laboratoriet av prøveserier fra tjæremilene, pluss prøver samlet inn fra andre produksjoner ble det utarbeidet en godkjenningsnorm for milebrent tjære. (Egenberg, FMF årbok, 129-130)

Det ble utarbeidet et produksjonsskjema for produsentene å fylle ut med opplysninger om tid og sted for brenningen, tyrikvalitet, mengde tyri og voksested for stubbene, milens konstruksjon, brenningens forløp, værforhold underveis, utbytte etc. Skjemaet sendes inn sammen med tjæreprøver til Riksantikvaren eller NIKU, hvis produsenten ønsker å selge tjære til bruk for stavkirkene. Hvis tjæren og tilhørende dokumentasjon godkjennes, får Fortidsminneforeningen beskjed om dette, slik at de kan foreta kjøp og salg (Egenberg, FMF årbok 2004, side 130)

4 1993 Godkjenningsnorm for milebrent tjære (Egenberg, 1993)

1993 Produksjonsskjema. Senere oppdatert i 2003

1993 Rapporteringsskjema for tjærebreing Senere oppdatert i 2009

1994 Riksantikvarens informasjonsblad om produksjon av tjære Senere oppdatert i 2005

1994 Riksantikvarens informasjonsblad om tjærebreing Senere oppdatert i 2002

I forbindelse med Egenbergs doktorgradsarbeid ble Produksjonsskjema og informasjonsblad om tjærebreing oppdatert. Der står det blant annet at … Tjærebreing av automatisk fredete kulturminner (stavkirker) eller andre bygninger av stor antikvarisk verdi skal dokumenteres og rapporteres ifølge retningslinjer fra Riksantikvaren (Riksantikvarens informasjonsark 3.9.12, 2002.)

5 • Produsentene leverer milebrent tjære til Tjærebanken når de vil. • Tjæren leveres til lager på Tangen i Hedmark. • Sortering skjer hos produsenten og på lager. • Pr i dag 3-5 produsenter, de fleste i Gudbrandsdalen

6 Produksjon, salg og beholdning av milebrent tjære, 2015-2018

År Mottatt Solgt Beholdning pr. 31.12. 2015 2150 2300 1680 2016 1400 900 2180 2017 1275 3600 - 145 2018 1200 975 80

Mottak gjennomsnitt pr år i perioden er 1500 liter.

Solgt gjennomsnitt pr år i perioden ca 2000 liter

1500 liter er omtrent utbytte av 1 mile, men jeg ser av tallene at hver av produsentene bare har levert 300 eller 500 liter. Hvorfor det skal jeg komme tilbake til litt senere.

Hvis man bruker 500 liter tjære på en stavkirke, ville årlig gjennomsnittlig mottak holde til 3 stavkirker årlig.

23 av de 28 stavkirkene er helt eller har deler tjærebredd, så med disse tallene ville det gå nesten 8 år mellom hver gang.

7 … Det er kun blitt mottatt og analysert prøver fra en enkelt milebrenning i 2008. … Rapporteringen milebrennerne mottar gir ikke detaljert informasjon om analyseresultatene, kun om innsendt prøver er innenfor normen eller ikke og eventuelt betraktninger rundt milebrenningsprosessen eller resultatet. De innsendt prøvene er altså ikke rangert med hensyn på kvalitet. NIKU har fått signaler fra tjæreprodusentene om at de ønsker noe mer detaljert tilbakemelding.

(NIKU rapport nr 1/2009, Tjæreprosjektet 2008, s.3)

Samme år, 2008, var beholdningen likevel 5000 liter. Salget/ forbruket samme år var ca.1500 liter, det vil si samme gjennomsnitt som siste periode (2015-2018). I årsrapporten for 2008 står det at Reidar Syverinsen i Tjærebanken mente at man burde ha ca 3000 liter på lageret hver høst for å dekke etterspørsel, i hvert fall ikke mindre enn 1500

Nå, høsten 2018, er Tjærebanken nesten tom slik den var vinteren 2002. Da sendte min forgjenger Fien ut brev til produsentene med ønske om kjøp av tjære. Jeg fant dokumenter fra 2008 der Fien nevnte 4 sikre leverandører, og heldigvis produserer 2 av dem.

8 Utfordringer og muligheter

• Pris, økonomi • Faglige miljøer • Kunnskapsdeling • Kvalitetssikring. Effektivisering? • Revidere produksjonsskjema og rapporteringsskjema. Nedlastbare? • Revidere Riksantikvarens informasjonsblad for produksjon av tjære og Riksantikvarens informasjonsblad om tjærebreing

9 10

10 Uvdal stavkirke, samling oktober 2017. Folk fra Fortidsminneforeningen, Maihaugen, Bygningsvernsenteret på Røros og Norsk folkemuseum 11

11 Uvdal stavkirke. Tjærebreing september – oktober 2018 utført av Meusburger AS. Foto: M.Winness 12

12 Nore stavkirke. Tjærebreing, september - oktober 2018, utført av Meusburger AS. Foto: Tor Meusburger 13