MSc Conservation and Restoration of Cultural Heritage Conservation Science
Master Thesis
HISTORICAL FORMULATIONS OF LAC LAKE PIGMENTS AND DYES: A STUDY OF THE COMPOSITIONAL VARIABILITY
By
Sanne Berbers 10193030
May 2018
Supervisors: Examiner: Dr. J. Dyer Dhr. Prof. Dr. ing. Dr. D. Tamburini M. R. van Bommel
Department of Scientific Research at the British Museum in London
Figure 1 Oinochoe of Canosa di Puglia, 3rd century BC, British museum, 1846,0925.26.A Lac sources in Hellenistic pigments
Samenvatting: Historische recepten van lac pigmenten en kleurstoffen, een studie naar de chemische samenstelling mei 2018 Sanne Berbers
Lac is een organische roze paarse kleurstof die onder andere gebruikt kan worden als textiel en leer verf of neergeslagen op een substraat als pigment. De belangrijkste kleurstof moleculen zijn laccaci acid A en B. De kleurstof wordt gewonnen uit de harsachtige secreties (stoklak) van de zogenaamde lakschildluis, (Kerria lacca kerr) een luisachtige die leeft op bomen in India, Cambodia en Thaiand. Van deze secreties wordt ook de hars schellak gemaakt. De stoklak bestaat uit kleurstoffen (4-8%) en schellak componenten (was 6-7% en hars 70-80%) om deze verschillende componenten van elkaar te scheiden wordt gebruikt gemaakt van de wateroplosbaarheid van de kleurstoffen en de onoplosbaarheid van de schellak componenten. Als gekeken wordt naar historische productie methodes is het aannemelijk dat een deel van de schellak componenten mee kwam in de kleurstof matrix tijdens de productie. Historische recepten geven aanwijzingen dat dit een bekend en ongewenst probleem was tijdens de productie van lak voor het verven van textiel. Er zijn echter ook aanwijzingen dat dit een gewenst fenomeen was bij de productie van pigmenten aangezien het kan bijdragen aan verfeigenschappen.
Om de mate van inclusie van schellak componenten in lak pigmenten en kleurstoffen te onderzoeken zijn test-monsters gemaakt. Hiervoor zijn eerst historische recepten afkomstig uit Europa bestudeerd, gedateerd van af het vroegst bekende recept uit de 9de eeuw tot aan recepten uit de 18de eeuw, waaruit de parameters met de grootste invloed op het productie proces werden gehaald, de pH en temperatuur. Aan de hand van deze informatie werden drie groepen monsters geproduceerd: i) pigmenten met kleurstoffen geëxtraheerd uit stoklak ii) textiel geverfd met kleurstoffen geëxtraheerd uit stoklak, en iii) pigmenten gemaakt door de extractie van textiel geverfd met lac. Het extraheren van kleurstoffen uit textiel voor de productie van pigmenten was veelvoorkomend in Europa van de 14de tot de 17de eeuw, en is daarom meegenomen binnen dit onderzoek.
Voor de analyse van de monsters is gebruik gemaakt van multispectrale fotografie en de analytische techniek HPLC-DAD-ESI-Q-ToF die recentelijk ook gebruikt is voor de chemische karakterisering van schellak. Aan de hand van deze resultaten kon geconcludeerd worden dat in het productie proces van lac altijd schellak componenten meekomen, zelfs als wordt gekeken naar de meest milde extractie condities namelijk kamer temperatuur en neutrale pH. De pigmenten die direct gemaakt waren van stoklak hadden de hoogste concentratie kleurstof moleculen en schellak componenten, variërend van vrije zuren tot penta-esters. De textielmonsters bevatten minder polyesters maar een grote verscheidenheid aan vrij zuren en diesters afkomstig uit schellak. Deze componenten werden voor het overgrote gedeelte overgedragen naar de pigmenten gemaakt uit de textiel. Hieruit werd geconcludeerd dat het onvermijdelijk is om tijdens de pigment of kleurstof productie schellak componenten mee te extraheren uit stoklak, tenzij gebruikt wordt gemaakt van moderne zuiveringstechnieken. Het voordeel van HPLC-MS als onderzoek methode ten opzichte van HPLC-DAD is met dit onderzoek geïllustreerd door de mogelijkheid van MS om ook niet of zwak gekleurde moleculen te kunnen detecteren die geen karakteristiek DAD spectrum hebben. De resultaten van dit onderzoek kunnen gebruikt worden bij de interpretatie van de analyse van een roze lake pigment gevonden op een hellenistisch terracotta oinochoe beeld (3de eeuw v. Chr.), waarin en laccaic acid A en schellak componenten waren gevonden.
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Abstract: Historical formulations of lac lake pigments and dyes, a study of the compositional variability May 2018
Sanne Berbers
Lac is an organic insect-derived pink-purple colourant which can be used as a dye for textiles and leather or precipitated onto an inert substrate as a lake pigment. The main colourant molecules are Laccaic Acids A and B. It originates from the resinous secretion of the oriental insect Kerria lacca kerr which is called sticklac, the same material from which shellac is made. A separation between the colourants (4-8%) and the shellac components (wax 6-7% and resin 70-80%) is generally obtained by an aqueous extraction of the water soluble laccaic acids while assuming the non- solubility of shellac in water. However, considering cruder historical production methods, it is plausible that shellac components are transferred into the colourant matrix, when attempting the separation. Historical recipes indicate that the inclusion of resinous components was a known unwelcome phenomenon in dyeing practices, whereas by contrast it might have been a desirable feature in pigments for manuscript illumination, as this afforded improved binding properties.
To study the significance of shellac inclusion within lac lake pigments and dyes, mock-up samples were made by reproducing a range of different historical recipes from Europe dating from 9th to 18th century. Particular attention was paid to some key parameters in pigment and dye production, such as temperature and pH. These parameters were used to create three different sample groups: i) pigments made with colourants extracted from sticklac, ii) textiles dyed with colourants extracted from sticklac, and iii) pigments made by extracting colourants from the dyed textiles. This last sample group was included as the production of lake pigments from textile clippings was a common practice in Europe from the 14th to the 17th century.
Multispectral imaging was carried out on all the samples which were also analysed by HPLC- DAD-ESI-Q-ToF, the latter being recently applied to the chemical characterisation of shellac. From these results it was concluded that shellac components were always present to some degree in the colourant matrix, even when considering the mildest colourant extraction conditions (room temperature and neutral pH). The pigments made directly from sticklac showed the highest amount of colourant molecules and the presence of shellac components, ranging from free acids to penta- esters. The textiles contained less polyesters but a wide range of free acids and diesters, which were transferred to a large extent into the pigments made from these textiles, due to the relative harsh extraction methods commonly used to extract pigments from textiles. From this it was concluded that the inclusion of shellac components within any lac pigment or dyed textile can be considered unavoidable unless more advanced refinement techniques are used. HPLC-MS has also shown its potential in comparison to HPLC-DAD due to its capability to detect non- or weakly coloured molecules that have no characteristic DAD spectrum. These data are finally useful to interpret the results obtained by analysing the pink lake pigment on a Hellenistic terracotta oinochoe (3rd century BC), where evidence of both laccaic acid A and shellac components was found.
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Table of Contents
Samenvatting ...... 2 Abstract ...... 3 1. Introduction ...... 5 2. Current scientific knowledge ...... 8 3. Research Methodology ...... 10 Historical recipes ...... 10 Mock-up samples ...... 13 Technical examination samples ...... 15 4. Results and discussion ...... 21 5. Concluding remarks ...... 34 6. Acknowledgements ...... 34 Bibliography ...... 35 Appendix I: Historical recipes ...... 39 Lac lake pigments ...... 40 Dyeing with lac ...... 44 Extracting lac from dyed textiles ...... 48 Miscellaneous other useful recipes and references ...... 51 Appendix II: Experimental information ...... 52 Appendix III: Multispectral Images ...... 55 Appendix IV: SEM images ...... 62 Appendix V: PCA of extended dataset ...... 65
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1. Introduction
A recent study into pigment use on Hellenistic terracotta’s at the British museum led to the examination of a decorative oinochoe wine jug, on which, among others, lac pigment was identified.1 This is a remarkable find considering that there are no contemporary uses of this pigment known to this date within Europe, the earliest currently reported European find of lac can be attributed to 7th-8th century lac dyed Merovingian textiles.2 One of the colourant molecules (laccaic acid A) and shellac components were found using HPLC-DAD-ESI-Q-ToF. Conventional organic pigment analysis using DAD as a detection method is limited because of its capability of detecting only coloured molecules. The addition of the mass spectrometer allowed for identification of the non- or weakly coloured components, such as the ones that originate from shellac, in the colour matrix. This can be specifically crucial for a pigment such as lac where the colorant molecules are prone to degradation but other- non colourant- residual components from the original material might remain detectable. This is dependent on the degree in which shellac components are transferred into the colour matrix during the pigment or dye production. More insights into pigment preparation, degradation and the molecular composition could aid in the further identification and knowledge about lac use throughout history.
Sticklac is the resinous secretion of the oriental insect Kerria lacca kerr, indigenous to India, Thailand and Cambodia, from which lac and shellac are produced. Lac is comprised of a group of anthraquinone colourant molecules: laccaic A and B in major quanites, and laccaic acids C, D and E in minor quantities. The hydroxyanthraquinonees erythrolaccin and deoxyerythrolaccin are colorant molecules which are also present in sticklac, but are considered part of the shellac matrix as they have a reduced solubility in water. Shellac can be characterised as a complex mixture of monoesters, polyesters of hydroxyl aliphatic and sesquiterpenoid acids. The exact composition of the resin is dependent on environmental factors such as the insect’s life, tree species it was growing on, the tree’s environment. A separation between the colourants (4-8%) and the shellac components (wax 6-7% and resin 70-80%) is generally obtained by an aqueous extraction of the water soluble laccaic acids while assuming the non-solubility of shellac in water.3,4 However, considering cruder historical production methods, it is plausible that shellac components are transferred into the colourant matrix when attempting the separation. Historical recipes indicate that the inclusion of resinous components was a known unwelcome phenomenon in dyeing practices, whereas by contrast it might have been a desirable feature in pigments for manuscript illumination, as this afforded improved binding properties.5 The possible presence of shellac pigments has also been noted in several studies on organic lake pigments.6
This master thesis will study the degree in compositional variability of lac as a result of changes in key parameters in the production process. Through an extensive survey of historical lac dye and pigment recipes, ranging from the earliest recipe found dating from the 9th century to the beginning of industrialisation in the 18th century in Europe, fundamental recipes were derived which allowed the study of different production parameters. This was utilised to produce three different mock-up sample groups: i) pigments made with colourants extracted from sticklac, ii) textiles dyed with colourants extracted from sticklac, and iii) pigments made by extracting colourants from the dyed textiles. Analysis with, among other techniques, multispectral imaging and HPLC-DAD-ESI-Q- ToF was employed to investigate the relationship between the production method and the molecular composition of the resulting lac pigments and dyes.
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The oinochoe vase which served as the starting point of this research is made from terracotta, has polychrome paint layer which is largely preserved and originates from the Hellenistic Greek period (323 – 31 BC) in Canosa di Puglia. A photographic reproduction of the vase can be found in Figure 1. Parts of the pink-purple paint layer remain present on part so the dress of the female figure standing on the top part of the vase. Analysis was done by J. Dyer and D. Tamburini at the British Museum on five samples taken from different areas of the dress.1 Microscopic analysis indicated a very underbound mixture of Egyptian blue and a pink lake physically mixed together, which was a common practice of the period.7 Analysis of the pink lake by HPLC-DAD-ESI-Q-ToF led to the identification of a mixture containing madder, coccid dye, shellac and tannin markers. From this the main colorant of the lake pigment was be identified as madder (Rubia spp.), the other markers led to the identification of insect-derived colourants from polish cochineal (Porphyrophora spp.) and lac (Kerria Lacca Kerr).
The markers for shellac included the colourant molecules erythrolaccin and deoxyerythrolaccin, and resinous components such as free acids and esters. The these colourant molecules have reduced solubility in water and their presence in lac pigment is considered to be indicative of a alkaline extraction of raw sticklac.6,8–10 The presence of resinous shellac components due to use as a consolidant during a conservation treatment was excluded by microscopic examination of the paint surface of the object. The markers for tannin can be indicative of a colourant which has been extracted from coloured textiles.6 The production of red lake pigments from coloured textiles was common in the 14th to 17th century throughout Europe, but has not been documented for Antiquity. The high value of colourants as a commodity does make it plausible that an effort might have been made to reuse colourants from clippings or worn down textiles. The presence of both shellac resin and tannins might be explained by the alkaline extraction of a textile source of lac, if the resinous component are transferred on a lac-dyed textile in the dyeing process and are then sequentially extracted with the colourant to form a pigment. It is known that resinous components can be transferred to textiles, historical recipes give warnings about the difficulty of dyeing with lac due to the high chances of resin transfer onto the textile.
It is often considered that lac was widely introduced into Europe with the invasion of the Iberian peninsula in the 8th century by the Umayyad Caliphate.10,11 This reinstated direct trading routes with the middle east which had been unreliable due to the turbulent period in Europe after the fall of the Roman Empire. An increase in archaeological evidence of extensive trading in recent years has created a shift towards the notion that these geographical limitations on trading were far less strict, and widespread trading with the middle east was continuous throughout history. Only limited number of texts survive from antiquity and information on craft practices was usually not deemed important enough to write about, instead it was disseminated through oral practice. However, circumstantial evidence can be found which supports the likely importation of lac from India to Greece during the Hellenistic period. The earliest written mention of lac as a dye can be found in India in the late Vedi period which corresponds to 1100-500 BC.12 Lac dye has been reported to be an export article from the city of Barygaza (Bharuch) in India which is mentioned by Pliny in the second century AD to be a source of pearl for well to do Roman ladies.13,14 This city is described in Periplus of the Erythraean Sea, a Greek – Roman text ascribed to the 1st century AD which describes navigation and trading opportunities of the time. The earliest references to lac found in ancient text are thought to be written by Aelian (ca. 175-235 AD), a Roman writer who wrote in Greek. His ‘de natura animalium’ is a collection of texts about animals where he describes, among others, the lac insect and the high value garments coloured with lac have. According to the text they are worn even by the Persian King.15 Although the precise date and origin of the text is
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difficult to determine due to the fragmented early Christian copies that survive today, it illustrates the likeliness that lac was known as a colourant in ancient times.16
The overall structure of this thesis takes the form of four chapters, including first a brief overview of previous findings of lac pigment and dye within literature. Then the research methodology will be discussed which is comprised of three sections, starting with a discussion on the historical recipes used and how they can be interpreted. Followed by presenting the mock-up samples and how they were made, and concluding with an introduction into the analytical techniques and why they were chosen to examine the mock-up samples. The next chapter is comprised of the results of the analytical examination of the mock-up samples and a discussion into the meaning of these results. The last chapter will conclude by reviewing the findings made in this research and how this could aid the future detection of lac on historical samples.
O
OH N H HO O HO O O O OH O O OH
HO HO OH OH HO OH HO OH O OH O OH Laccaic acid B Laccaic acid A
NH2 O
HO O OH O CH3 O OH O O OH
HO HO
OH HO OH HO OH O O OH Laccaic acid D Laccaic acid C
NH2
HO O O OH O O OH
HO
OH HO OH HO OH OH O O OH Erythrolaccin Laccaic acid E O OH
HO OH
O Deoxyerythrolaccin
Figure 2 Molecular structures of the colourant molecules present in sticklac
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2. Current scientific knowledge
This chapter will discuss different findings of Lac in historical pigments and dyes which have been reported by literature. Lac appears to remain an elusive pigment, although lac is mentioned as a colourant in historical texts from earlier dates, when consulting literature it appears to be found on objects in Europe ranging from the 8th century onwards.17,18 A discrepancy can also be seen between the occurrence of historical findings of lac as a pigment and lac as a textile dye. The earliest European textile finds which contain lac can be attributed to the 7th century whereas until recently the earliest known uses of lac pigment in Europe can be attributed to 11th century Portuguese illuminated manuscripts. The historical recipes used to manufacture mock-up samples which are discussed in the next chapter further complicate the lac timeline, the earliest recipe found by the author describing dyeing with lac originates from the seventeenth century opposed by the first recipe for a lac pigment dating from the 11th century.
There are two possible explanations for why the history of Lac remains complicated. First of all, the colourant had to be imported from India to Europe, the scale of this remains largely unknown and has not been studied in detail. It is possible that pigments and textiles made their way to Europe much earlier than the unprocessed stick lac which could have started at a later date, in this case it might even be possible the exact source of the colourant was unknown to the user. A second reason might be found in the detection methods for lac pigments. Laccaic acids have proven to be very vulnerable to acid hydrolysis, which occurs during the commonly used dye extraction method with hydrogen chloride.2,19 More recently a two-step extraction was introduced a soft extraction followed by a slightly more aggressive extraction with a small concentration of oxalic acid in order to obtain all possible colourants without causing degradation.20–23 The first step extracts all direct and vat dyes, and the second step the mordant dyes. This ensures that all possible colourant components are extracted intact to be analysed and possible glycoside decomposition is avoided.24 In conjunction with this development analytical methods have become more sensitive allowing better detection of small concentrations of compounds from very small samples. This creates possibilities for the detection of lac where it might have been missed in the past.
The earliest known samples of lac in Europe to date which can be found consist of historic textiles. Wouters et al. found lac on a Merovingian silk textile dated to the 7th-8th century where it is mixed with madder.2 And more recently Lac was identified on Coptic textiles dating from the 30 BC to 7th century together with madder.25 Lac was also documented to be found on Coptic textiles dating around 900 A.D. where it was identified as the single colourant on wool.18 Pfister and Verhecken suggest that Indian lac was introduced in Egypt after it was conquered by the Arabs in the 7th century, where it was then used as a rival to madder in red colouring.26 However recent believe is that trade was much more fluent than original thought and only an increase in trade occurred due to easier trading routs, making the east more accessible and therefore cheaper, which is why it is found more after the 7th century. Eastwood found Roman textiles at Quseir al Qadim , double dyes blue and red – 1st/2nd AD indigotin + madder, which considering the mixture of dyes might be a suspect for undetected lac pigment.27 From the same site, later 13th – 16th century samples containing lac AD on wool were also found. Most lac dyed textiles appear to be silk, this could be due to the expensive nature of the dye which would most commonly be used on expensive materials, especially when these textiles would be exported.28,29
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Lac is often not found as the single textile dye but in combination with madder.2,18,25,30 Madder was possibly used to obtain a certain hue together with lac, either as a mixture in the same dye bath or by overdyeing in sequential dyebaths. Madder could also have been used as an adulterant, to supplement the more expensive and exotic lac dye. Another explanation might be that in these historical textiles the warp which is not visible was dyed with madder and only the visible weft was dyed with the more expensive lac. Thought could be given to the revaluation of some historical textiles on which madder was found during old analysis to see if lac could be found with the new standards of analysis available now. Research by Petroviciu et al indicates that the combination of lac and madder was the primary red dye in the supporting silk fabric for 15th and 16th century Romanian religious textiles.31 They propose an oriental origin for these materials because of the apparent absence of large scale lac dyeing in Europe. Together with the growing understanding that lac is often found in combination with madder gives reason to suspect that there might be more evidence of the use of lac dye on dyed textiles which have been identified as madder dyed. Interestingly this apparently common practice of dyeing lac together with madder is not reported in any historical recipes for dyeing with lac.
Outside of Europe Gleba et al report the identification of lac pigment in combination with munjeet on a wool sample originating from the 5th-7th century in Nepal.32 On this sample resin components were identified which could indicate the presence of shellac. Since it is known that lac was used for dyeing in India since around 1500 BC it would be expected to find historical findings of lac dyed textiles. However this is not reflected by literature as no scientific analysis of ancient lac dyed Indian textiles could be found, if this is due to linguistic barriers remains unclear.
The first known European finds of lac lake pigments seems to be originating in the Iberian Peninsula. Melo identified lac paint in the illustrations of ‘the book of birds’ 1183-1184, no5, ff. 6 and 73v from Lorvão manuscripts from Portugal.33 They were made in St Mamede of Lorvãdo (São Mamede do Lorvão) currently at the Arquivo Nacional da Trore do Tombo (ANTT). Portugal was then under Islamic rule, lac came to the Mediterranean in the 11th century through Arab commercial trading routes with local Jewish partners.11,34,35 Lac was also found in the red paint layers on two different icons, both red lake paints bound in egg, from different cities originating from around the 12th century Cyprus orthodox tradition.36 On one Icon the lac was found as a pure pigment in a paint layer and in the other icon it was found together with redwood. These finds might reflect trade routes of the Arabic world into Europe but the authors note that more research need to be done into icons from this early period for confirmation. Kirby et all describe lac lake being used in a number of European easel paintings, with the earliest example being found in a false enamel decoration on the Westminster Retable (London, Westminster Abbey) dated to around 1260-80.6 These and other samples in later paintings all contain traces of shellac components, indicating an alkaline extraction of the pigment from sticklac.
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3. Research Methodology
The methodological approach taken in this thesis research is a combination of historical recipe research, the creation of mock-up samples based on these recipes, and the technical examination of these samples using several different analytical techniques. These three different research strategies will be discussed separately below.
Historical recipes Careful consideration has to be taken when reviewing historical recipes for lac pigments or dyes. When organic colorants are precipitated on a substrate to create pigments they are called lake pigments, the terminology regarding red lake pigments presumably has its origin in Sanskrit word for lac, laksha, which was simultaneously used for both lac, shellac and sticklac. The distinction between a red lake pigment made from other sources (such as the plant material madder, and the insect sources Kermes and cochineal) and a lake pigment made from lac is often difficult to discern in historical sources because the word lac and lak are used intermingled, some of which can be found in Table 1. Table 1 Common names for lac throughout history
The earliest reference known today Common Dutch Laklak 22,27,37–39 which alludes to the use of lac can be found in names English Lac dye, lac lake Finish Lakka India, where it is mentioned for its medical French Gomme Laque, lac lac purposes. India had been the centre of lac German Lic-lac production and use since the Vedic period Italian Lacca which is 1500-600 BC.12 None of these early Spanish Laca Persian Lak Indian manuscripts describe dyeing recipes, Hindu Lakh, Lakha nor are there surviving recipes from this time Sanskrit lākshā (������) period from other parts of the world. The Synonyms Bengal lac, cake lac, caked lac, recipes used in this thesis come from various gummilack, grained lac, kadi lakh, seed- lac, rangbatti, sources, such as manuscripts and dyers manuals, with dates ranging from around the 9th century to the 18th century. These generally have complicated origins as the surviving texts are often known to be copies of earlier texts which are now lost. An overview of recipes and their text used can be found in Appendix I. A summary of the recipes and their most important parameters is listed in Table 2.
There are different historical recipes that mention the production of a pigment/dye from sticklac. They can be considered in three categories: the lac colorants are extracted and precipitated on Al3+ to form a lake pigment, the lac colorant is extracted from the sticklac source and left in solution as a colorant or the lac colorant is extracted and used to dye textiles. Although the use of textile clippings for the production of lake pigments was common practice between the 14th and the 17th century in Europe, it seems to be used primarily for kermes, cochineals and madder. It is thought that lac and brazilwood lakes were more often made from the raw dyestuff source.22 This is corroborated by the fact that none of the recipes for making lake pigment from textile clippings specifically mention lac dyed textiles. Cennini even advised against the use of lac lake made from textile clippings, this is an indication that lac pigment was being made from textile clippings but considered as bad practice.40
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Table 2 An overview of the different recipes, their main ingredients and important observations as recorded in the recipes. The complete recipes and their sources can be found in Appendix I
Recipe Type Date Urine Ley Colorant Precipitation Notes extraction J. Le Begue Lake 1431 boiled Urine or ley Boiled Roche alum and After §12 pigment Sal gem with ley precipitation 15 boiling days in urine/ley J. Le Begue Lake free 1431 Very old, - With raw lac And alumina §36 colourant then boiled 4:1 zuccarino J. Le Begue Lake free 1431 3 days old - Keep lac in Roman vitriol – §37 colourant urine 3 days sulphuric acid then boil Bolognese Lake 15th Week old Create ley Warm Roche alum cold §129 pigment then boiled from that urine Bolognese Lake 15th 20 days old - In boiling old Precipitation §130 pigment then boiled urine with direct during roche alum extraction Natural Lake Modern - Potassium Simmering Potash, 50 °C Ley is replaced by colorants pigment adoptation carbonate potassium and dyes solution carbonate Ibn Badis Lac c. 1025 - Borax and Boiled Used free in colourant sodium solution free in carbonate solution Mappae Lake 12th or 9th Urine boiled Boiled Alum Clavicual pigment to reduce Ziegler Dyed with 1677 - Tartar and Boiled Yarn in bath for brazil alum 30 min when still wood hot bath Plichto Dyeing silk 1548 - - Warm water, Tarter, alum Boil silk with italian extract 2 times mordanted silk, black soap, roche boil for 1 hour alum 2 days Cardon india Dyeing silk - - Overnight cold Alum dyeing, water cold/hot? Hellot Dyeing 1789 - - In linen sack, Boiling Bad because it wool boiled includes the resins through the boiling Hellot Dyeing 1789 - - Boil, cool Let After wool particles sink concentration to bottom dye with it, boiling with alum and tartar Hellot Dyeing 1789 - - - - Several methods wool to incorporate less resin, which use other types of ingredients J Le begue Lake from 1431 - Ley from ashes Boil ley with More ley, with Not specifically §11 clippings clippings alum, add liquid for lac , scarlet rubea de grana J Le begue Lake from 1431 Urine (no Clippings in No alum, from §13 clippings time urine for some scarlet of rubea specified) days de grana Nuremburg Lake from 15th - Ley from Boiling ley Grind with alum Paris red from Kunstbuch clippings ashes, boiling with clippings Boil agian red clippings Bolognese Lake from 15th - Ley of ashes Boil clippings Adding roche Rosato clippings §110 clippings strong with ley alum until precipitated, stirring until cool Bolognese Lake from 15th - Ley from ashes Boil clippings Add roche alumn §111 clippings and quicklime with ley and boil (CaO)
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When using recipes from historical manuscripts it is necessary to keep in mind that the recipes are usually very subjective to interpretation. Often translations of the original text are used, and it is often known that the original text is also a copy from an earlier text. The recipes vary in detail; most do not give quantities or time scales and assume things are common knowledge which they are no longer. Further considerations have to be made regarding the materials referred to in the recipes and how they relate to modern materials. This can also be related to the fact that these recipes were often not written by craftsmen but by scholars observing the practices of craftsmen. It is known that these types of recipes often contain some omission of essential parameters, which are either unknown to the author of the recipe, a secret or thought to be common knowledge and therefore omitted. Especially in dyeing practises the recipes were carefully guarded, craft secrets, only transferred verbally and through people directly associated with a dyeing workshop. There are two ways to approach the reconstructions resulting from the recipes as discussed above, one is to exactly follow the historical recipes and see how they result in different types of pigments. But these recipes allow for a large amount of interpretation on important parameters such as amounts and times. The other option is to use the important parameters in each recipe and from this create more analytical reproducible recipes with controlled parameters, as was introduced by Kirby et all in the book ‘Natural Colourants’.22 In the three sections below these important parameters for each type of recipe will be identified. Lac pigment Most recipes which describe the production of lake pigments directly from the sticklac pigment sources consist of two essential steps which can be considered general for all lake pigments. The first step is the addition of an alkaline solution to extract the colourant from the resin (often accompanied by heating) followed in a second step by the addition of alum to precipitate the pigment.
Both these steps require an alkaline solution, although most of the colourant molecules are water soluble, the extraction process is much more effective and faster in an alkaline environment. The precipitation of the lac colorant molecules on Al3+ by the addition of alum to form an insoluble metal–dye complex needs an neutral to alkaline environment to achieve good precipitation. Laccaic
acid has three pKa values at 5.6, 7.0 and 9.8 which are corresponding to different shades of lac pigment so the pH can also be adjusted to the requirements of the resulting pigment.5 The use of urine to create an alkaline environment is a common practice throughout history. By heating the urine together with ashes a very alkaline solution called ley could be obtained. It is unknown if there is an added value to the other additives which are present in urine. It was used in dyeing practices to scour the wool, remove the grease and clean the wool as preparation for the dyeing process.41 In this process the ammonia, which is formed when heating the urine, plays an important role. When the solution is too alkaline it can damage the wool fibres.
Dyeing with lac Dyeing with lac was done in a three stage process where the colourants were extracted from the sticklac, the textile was mordanted and the textile was consequently dyed with the extracted colourants. There are three factors which vary between the different recipes; extraction temperature, the dyeing time (which is a variable parameter for every dyestuff), and the addition of potash to the dyeing pot. Often the colorants are extracted in a neutral environment, with cold water over a longer period of time. Extraction of the dye under higher temperatures contributes to the inclusion of resinous components in the dyebath. The sub-sequential dyeing is then done with alum mordanted textiles in several dye baths, sometimes the textiles are mordanted repeatedly in
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between the dyebaths. The recipes do not indicate alkaline solutions were being used for the extraction of the colourant. This could have several reasons, it might be the different colours which can be obtained from lac at different pH are not maintained due to the pH environment on the textile. Or perhaps dyeing with lac at high pH is not feasible, there seems to be no indication that dyeing with slight alkaline pH is damaging to the silk fibres, whereas it is damaging for wool.42 In other dye recipes potash is often added to the dyebath which increases the pH and sometime the colour of the resulting dyed fabric. Many dyes show a shift in colour when the pH of the dyebath is changed, but this does not always result in a different colour on the textile, as might be the case for lac. There is one recipe by Plichto (§118 see Appendix I) which mentions the addition of cream of tartar to the dye bath; changes the pH of the solution but was added to remove calcium from water which is not necessary when using demineralised water.22,39 This is general for all the recipes, some note to use the cleanest water possible, or only from a fast streaming river. It is assumed that the use of soft water with a minimal amount of minerals was considered common practise. Lac pigment from textile clippings Recipes for the production of pigment from textile clippings consists of two steps: the extraction of colourants from the clippings, and the addition of alum to precipitate the colourant molecules. The recipes to extract lake pigment from textile clippings used here are meant for the extraction of madder or cochineal. These were used because the lack of recipes specifically for the extraction of lac pigment from clippings. The textile extractions are usually done in an highly alkaline environment, with variations in temperature and time. Dyed silk requires less aggressive extraction methods than dyed wool because the silk binds less strongly to the dyestuff.22 In some recipes the fibres are disintegrated by the alkaline extraction and material is incorporated into the final pigment. This is more likely to occur when using wool clippings which contain a higher amount of sulphur that dissolved causing the protein structure of the wool to disintegrate.6 Mock-up samples Following the considerations described above, three different mock-up sample groups were made: i) pigments made with colourants extracted from sticklac, ii) textiles dyed with colourants extracted from sticklac, and iii) pigments made by extracting colourants from the dyed textiles.
There are two genera lac-dye insects, Kerria and Paratachardina, but research by Santos et al has shown that only the Kerria type contains sufficient red colorants molecules to be used.8 Within Kerria lacca several different species can be identified which are used as dye: laccifer lacca, Carteria lacca, Tachardia lacca and Lakshadia lacca.43 According to the supplier, Kremer Pigmente GmbH & Co. (Aichstetten, Germany), the sticklac used in this research originates from the species Tachardia lacca.
Research has shown that there are three important factors that determine the solubility of shellac, and thus the amount of resin which is incorporated into the final pigment: the temperature and pH used during manufacturing and the age of the raw sticklac. These are also factors which are often left open to interpretation in historical recipes. The resin fraction becomes more soluble as the pH and the temperature during the extraction of the colourants go up. Heating the sticklac to above 60⁰C when it starts melting, and a pH above 8 for extraction promotes the incorporation of resin.10,44 Research by Farag et al has shown that there is a significant decrease in the solubility of shellac resin when one year old resin is compared to 5 year old resin due to the polymerisation of the resin network.45 The raw sticklac available at the British Museum was 10 years old, for that reason new sticklac was ordered from Kremer Pigmente GmbH & Co. (Aichstetten, Germany). They report the acquirement of the batch of sticklac currently sold in March 2017, which allows for the assumption
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that the sticklac used is around 1 year old. The increased solubility of the shellac fraction is likely to contribute to an increase in the amount of colourant molecules extracted from the sticklac and releases them from the polymer network in which they might been encapsulated. When the polymer network is not broken down the extraction of the colourant molecules from the polymer network is dependent on the solubility and diffusion of these molecules through the shellac polymer network. Extraction then becomes dependent on the age of the shellac and the extraction time, this is reflected in the historical recipes where cold colourant extractions are often done over long periods of time.
It is known that lac does not bind well to plant fibres, excluding cotton and linen for substrate fibres, but ancient examples can be found of silk and wool dyed with lac.38 There is a high likelihood that only expensive fabrics such as silk were transported from India to Greece in the Hellenistic period. The presence of tannins in the paint samples from the terracotta oinochoe vase is an indication that silk clippings were used as source for the pigment.1,6 Silk was often weighted using tannins which, if silk clippings are used as a source for colourants, are consequently extracted together with the colourant molecules and end up in the resulting pigment.
In view of these consideration and an attempt to limit the scope of this research it was decided to only focus on silk as textile clipping source and exclude wool. Assuming that the silk is degummed no further pre-treatment of the silk is necessary except for the mordanting which is discussed further onwards. Although the presence of tannins influenced this research in the direction of silks and pigments made from clippings, the silks used in the mock samples are not weighted. There is little information known about the weighting of silks, research by Hacke shows that the earliest areference of weighted silks in Europe can be found in court records of 1606.46 There is no documentation to be found on earlier historic weighing practices or oriental weighting practices. In conjunction to the weighting of silk, tannins could also be used as a type of mordanting.38 Sources of tannins include a wide variety of materials: sumach, gambier, chesnut, alder bark, gall nuts, catechu, myrabolams, valonia, acacias and divi divi.38,46 Stick lac naturally contains pieces of bark from the tree where it originates from as the material is deposited on the bark, which can also be seen as a possible source of tannins. Within this research is was decided to use unweighted silks to limited the scope of the research and to evaluate the possibility of the introduction of tannins through pieces of tree bark in the sticklac. The silk was dyed as a plain woven textile, as this was the material readily available within the British Museum.
Lac is a mordant dye, and the mordant used in each of the historical recipes is alum. It is more common to uses alum in European dyeing practices for insect based dyes; however in Asia iron was also often used. Iron mordanting was often used in combination with tannin weighting for dark colours through which even larger amounts weighting could be achieved.38,46 Because the scope of this research is constricted to Europe it was chosen to solely use an alum based mordanted textile. The mordant changes the colour of the dye, aluminium gives a crimson colour and iron a more purple colour (tin gives a scarlet colour but was not used until the 17th century).38 Silk should never be in a bath with a temperature above 70°C which was taken into consideration when dyeing47.
Taking into consideration the important experimental factors determined from the historical recipes, standard procedures for mock-up samples were made, by adapting the standard recipes for organic lake pigments by Kirby at all as published in their book Natural Colorants for Dyeing and Lake Pigments.22 This resulted experimental procedures which can be found in Appendix II and the resulting samples of which a list as can be seen in Table 3 and 4 . Extractions at high temperature indicate boiling point for 10 min, whereas room temperature signifies an extraction of three days. A distinction is made between the samples which are presented in the two tables, Table 3 shows the
14 Berbers, Uva 2018 Lac sources in Hellenistic pigments main sample group which were made by varying only the temperature and the pH of extraction. Table 4 represents other samples which were made during the course of this research and investigate other experimental parameters of the manufacturing process. The pigments made from textile clippings are called textile pigments, whereas the pigments made directly from the sticklac are called direct pigments.
Table 3 List of samples and names, the abbreviation in the sample names stand for: P) pigment ;DP) direct pigment made from sticklac; TP) textile pigment, a pigment made through extraction of colourants from a dyed textile; Tu) dyed textile unaged; Ta) dyed textile aged; H) hot extraction of colourants at boiling point; C) cold extraction of colourants at room temperature; N) at a neutral pH of 7; A) at an alkaline pH of 11; 1) textile dyed once; 3) textile dyed 3 times with mordanting in between.
Sample Name Description of the main experimental parameters in the production of the sample P Lac dye, Kremer pigmente, 36020 pure colourant DP_H_N High T, pH 7 extraction DP_C_A Room T, pH 11 extraction DP_H_A High T, pH 11 extraction TP_C1_C Pigment made from textile Tu_C1 by room T and high pH extraction TP_C1_H Pigment made from textile Tu_C1 by high T and high pH extraction TP_C3_C Pigment made from textile Tu_C3 by room T and high pH extraction TP_C3_H Pigment made from textile Tu_C3 by high T and high pH extraction TP_H1_C Pigment made from textile Tu_H1 by room T extraction and high pH TP_H1_H Pigment made from textile Tu_H1 by high T and high pH extraction TP_H3_C Pigment made from textile Tu_H3 by room T extraction and high pH TP_H3_H Pigment made from textile Tu_H3 by high T and high pH extraction Tu Undyed silk Tu_C1 Room T extraction, dyed once rd rd Tu_C3 Room T extraction, after 3 mordanting and 3 dyebath Tu_H1 High T extraction, dyed once rd rd Tu_H3 High T extraction, after 3 mordanting and 3 dyebath Ta Undyed silk Tu aged one month Ta_C1 Dyed silk Tu_C1 aged one month Ta_C3 Dyed silk Tu_C3 aged one month Ta_H1 Dyed silk Tu_H1 aged one month Ta_H3 Dyed silk Tu_H3 aged one month
Table 4 List of samples and names, the abbreviation in de sample names stand for: P) pigment ;DP) direct pigment made from sticklac; TP) textile pigment, a pigment made through extraction of colourants from a dyed textile; Tu) dyed textile unaged; Ta) dyed textile aged; H) hot extraction of colourants at boiling point; C) cold extraction of colourants at room temperature; N) neutral pH; A) alkaline pH; 3.1/3.2/3.3) the same dye bath in which three consecutive pieces of silk are dyed.
Sample Name Description of the main experimental parameters in the production of the sample
DP_H_A_T Extracted pigment, after unsuccessful dyeing of silk TU_H_A at high pH and high T DP_H_U Urine, high T extraction TP_H3.1_C Pigment made from textile TU_H3.1 by room T extraction and high pH TP_H3.1_H Pigment made from textile TU_H3.1 by high T and high pH extraction TP_H3.2_C Pigment made from textile TU_H3.2 by room T extraction and high pH TP_H3.2_C Pigment made from textile TU_H3.2 by high T and high pH extraction st Tu_H3.1 High T extraction, 1 silk dyed in dyebath nd Tu_H3.2 High T extraction, 2 silk dyed in same dyebath rd Tu_H3.3 High T extraction, 3 silk dyed in same dyebath Tu_H_A High T and high pH extraction Ta_H3.1 Dyed silk Tu_H3.1 aged one month Ta_H3.2 Dyed silk Tu_H3.2 aged one month
Technical examination samples
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Many different techniques were used to examine the samples after they were made. This section will briefly introduce those techniques and explain why they were used and to what means. The specific technical details of each technique can be found in the experimental section of Appendix II. Care must be taken when comparing the different samples to each other with each of the described techniques. Analysis of the textiles should be viewed separately from the pigments because of the medium difference. Although care was taken the same quantities were used to produce each sample within each sample group, this is was impossible between the sample groups. This creates difficulties when comparing the textile pigments with the direct pigments. It is impossible to estimate the concentration of colourant molecules extracted from the textiles and how this relates to the concentration of colourants extracted to create the direct pigments. However the relative ratios of compounds can be used as a comparative feature as this remain the same when the total concentration is altered. Multispectral imaging Multispectral imaging is the term used to describe the employment of different sections of the electromagnetic spectrum to visualise the characteristics of materials under these types of light. In this case a modified camera, filters and different light sources were used to capture this. By using standardised photography settings, colour calibration and post processing these images can be used to deduce scientific results. In this research the settings standardised by the CHARISMA working group have been used.48 Often false colour images are used to highlight these differences and make the information more comprehensible. The visible reflectance images (VIS) are made by blocking all the ultraviolet (UV) and infrared (IR) light from entering the camera detector, resulting in an image that records the wavelengths between 400-700 nm. The ultraviolet reflectance (UVR) is made by using UV lamps resulting in the capturing of the reflected UV radiation (200-400 nm) by blocking the VIS and IR parts of the spectrum . The resulting image captures the ability of the subject material to reflect the UV light. Ultraviolet induced luminescence (UVL) uses UV radiation and records the resulting VIS light (400-700 nm) induced luminescence. Reflectance infrared (IIR) uses a filter to block all UV and VIS light and visualises the IR light which is reflected (700-1100 nm). Visible induced visible luminescence (VIVL) records the emission of light in the visible region (500-700 nm) induced by a different part of the visible light spectrum (400-500 nm). Colourimetry When studying samples of which colour is a parameter of interest, a way needs to be found to quantify and describe the way the colours are perceived by humans. This is called colourimetry and can be done in multiple ways, usually by recording the colour spectrum and translating this to values in a colour space. There are special spectrophotometers which have a day light lamp that emit a specific known colour spectrum. From this the calibrated colours in a specific colour space can be calculated. The downside of this is that the colour needs to be on a homogeneous flat surface, making it impossible to measure loose pigments. Another way to calculate colour values is to usespace colour calibrated images and average the colour values using a processing tool. These values are obtained under less controlled conditions and less accurate because they do not take into account the irregularities in the surface of the subject. But this feature is also what makes it possible to get an indication for the colour values of samples such as loose pigments. The colour space used was the CIE L*a*b* (CIELAB) introduced by the international commission on illumination. It uses three different coordinates to describe colour: L* represents lightness with 0 being black and 100 diffuse white, a* green for negative values and magenta for positive values, b* blue for negative values and yellow for positive values. To evaluate the colours irrespective of the lightness only the a* and b* values are often used in two-dimensional model. The lightness values can be neglected
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because they are determined by the colourant concentration and can thus only be viewed per sample group. HPLC-DAD-ESI-Q-ToF High-performance liquid chromatography – diode-array detection - electrospray ionisation – quadrupole – time-of-flight (HPLC-DAD-ESI-Q-ToF) comprises of three different components. First is the chromatographic separation technique (HPLC) which separates a liquid sample according to the molecular structure of the different analytes present in the sample. Then two sequential detection techniques, DAD is a non-destructive method that uses light to measure the absorption of the eluent coming from the HPLC. Followed by a mass spectrometer (MS) which couples quadrupole magnets with a time-of-flight set-up to detect the mass to charge ratio (m/z) of each molecular species present in the eluent as it enters the machine. This can be translated to an accurate mass for the molecules. The ionisation method used is electro spray which is considered a soft ionisation mode that allows the molecules to be ionised without breaking the molecular structures. The MS has a double function with two parts, it can be used with both parts functioning as an MS which is called MS/MS mode. The quadrupole then works as a selective ion filter after which the selected molecules are detected by the ToF. This function is useful when dealing with unknown compounds, the molecules break down from which the original molecular structure can be deduced. However thanks to the work done on the molecular composition of shellac by Tamburini et al. this proved unnecessary.49 The quadrupole was used to focus the molecular ions and the ToF was used to record the m/z values.
DAD can be considered as a quantitative technique due to the linear relationship between the intensity of the signal and the concentration of analytes responsible for the signal over a range of concentrations, as proven by the law of Lambert-Beer.50 It has its limitations in the fact that it can only detect coloured molecules in non-absorbent mobile phases and the sensitivity for low concentration of analytes is problematic as deviations from linearity occur.
The DAD measurement was recorded at 491nm as this corresponds to a high intensity area for laccaic acid A and B. The peaks were integrated and adjusted to their possible dilution factor and the sample weight used in the extraction. The difference in substrate unfortunately makes it impossible to normalise the textile samples to the pigment samples. The average of the normalised integrated peak area of the measurements in triplo was used in the final results. For some measurements no significant DAD signal was obtained. This can be attributed to so called hyphenation problem of coupling a MS detector to a DAD detector. Both detectors have different requirements of the HPLC system and analytes. The DAD detector requires relative high concentrations of analytes and volumes (which can be translated to high flow rates). MS systems require the opposite, low concentrations of analytes as they are very sensitive, and low flow rates to obtain complete ionisation. The ESI ionisation technique is one of the few which can be used in combination with a DAD detector as it can function with higher flow rates. However all analytical conditions from the sample preparation to the system were optimised for MS functionality and not DAD.
Mass spectrometry, as used during this research, is not a quantitative technique due to ionisation discrimination. Not all molecules are ionized by the ESI and some molecules ionise more easily than others which results in those molecules being detected at a higher intensity than others. Quantification can only be achieved when know reference standards can be used of each analyte of interest, which are not available for all molecules of interest in this research. Although the intensity of the signal is not quantitative, it can be consistent across a sample and be used as an indication of the relative ratios within compounds. The systematic error caused by the instrument was evaluated
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by measuring each extracted sample in triplo. If the peak areas remain within statistical agreeable limits this can confirm that although the ionisation is discriminative, it is consistent across the samples and can be compared for this system. The random error caused by possible inhomogeneity within the mock-up samples and the experimental conditions was not evaluated. The triplo HPLC measurements were all done from an extract taken from one sample taken from the corresponding mock-up sample. Although this can create uncertainty within the results, this is consistent with general museum practise. Due to the value of historical objects and their function inside museums samples are only taken in a very limited manner, it is very rare to have enough samples to obtain statistically sound results. Each mock-up sample was only made once, making it impossible to evaluate the variation causes by the production method.
In order to effectively compare the MS spectra of the different samples a selection of sixteen molecular species was made that represents the different free acids, esters and polyesters present in shellac as well as the colourant molecules Laccaic Acid A and B, Erythrolaccin and Deoxyerythrolaccin. They were chosen by considering the molecular composition of shellac and their abundance within the sticklac matrix. A list of these molecules and their exact m/z value can be found in Table 5. The separate MS spectra of each sample were evaluated separately as there are a lot more different molecules present in the sample matrix than the sixteen presented in Table 5. However a complete characterisation of these spectra did not proof to be feasible in the scope of this research as it did not aid in answering the research questions. From previous research the elution time of the molecules of interest was known, which was used in combination with the accurate m/z value to determine the molecular ion peak within the total ion current (TIC).49 The integrated peak areas of all detected molecules per sample were summed from which they were normalised to 100%. Each sample was measured three times, the percentages were calculated for the separate measurements, after which an average of the relative peak area was taken. The standard deviation was calculated over the three relative peak areas calculated per measurement. The total standard deviation was calculated by averaging the standard deviations over all samples per molecule of interest. PCA Principle component analysis was used to interpret the MS data. It uses a statistical approach to create a different visualisation of the data which makes it easier to identify the variations and similarities that exist within the dataset. It does this by converting the data into so called principle components, directions in which the data shows the most variance. Then, these become the new axis on which the data are projected instead of the x and y axis. This is mathematically done by deconstructing the data set into eigenvalues and eigenvectors. These represent the respective degree of variance and the direction of the variance, the eigenvector with the highest eigenvalue becomes the first principle component – the x axis. The number of eigenvalues – vectors corresponds to the amount of variables exist in the original dataset. But the PCA identifies and quantifies the variables which contain the most variation, and thus the most interesting information. This becomes especially useful when the dataset contains a large amount of variables, as is the case in the dataset obtained from the HPLC-DAD-ESI-Q-ToF measurements. The PCA calculations were done using EXSTAT extension of Microsoft excel, information on the calculations can be found in the experimental section of Appendix II. An important last step in the PCA is identifying which variables are represented in principle components and what kind of variation (positive or negative) they represent. To visualise the difference between colourants from lac (Laccaic Acid A and B) and the often shellac associated colourants (Erythrolaccin and Deoxyerythrolaccin) these were summed for the PCA analysis. It was also decided to sum all the polyesters to create a more comprehensible PCA. The tannin source Ellagic Acid was excluded from
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the PCA as it distorted the PCA due to being uncorrelated to the other variables and clear to interpret. FTIR Fourier transform infrared spectroscopy was used as an preliminary research tool. It is a technique that measures the vibrational spectrum of molecular bonds by the characteristic absorption of IR radiation. This can give information about the molecules and their molecular environment. When looking at more composite materials such as the samples in this research this can become more complicated, as some materials such as the silk textile might give a very high intensity signal causing other signals to become more difficult to see and interpret. Scanning electron microscopy Scanning electron microscopy (SEM) was employed to evaluate the condition of the textile fibres before and after the dyeing process and the extraction of colourants. By looking at the fibres under high magnification and high resolution any damage that might occur during the production process can be seen. Ageing Ageing experiments were done on the textile samples. Because the textile surface does not require binding medium, it allows for a preliminary indication of the behaviour of the lac colourants and any shellac components which might be present and the possible difference in degradation between them. The original samples from the Hellenistic terracotta sculpture were so under bound that it was not possible to determine the binding medium. Evaluating the pigments in binding media would have required more research and unfortunately proved to be out of the scope of this research. Ageing was done under visible light, without UV, at temperature of 40°C and a relative humidity of 50%.
Table 5 The molecular species investigated using HPLC- DAD-ESI-Q-ToF and their accurate m/z value.
M/z Name Component type PCA data manipulation 243.1996 Butolic acid Free acid from shellac 263.1298 Laccijalaric acid Free acid from shellac 269.0455 Deoxyerythrolaccin Colorant from shellac Summed with Erythrolaccin for PCA 279.1238 Jalaric acid Free acid from shellac 285.0405 Erythrolaccin Colorant from shellac Summed with Deoxyerythrolaccin for PCA 300.99 Ellagic acid Tannin Excluded from PCA 303.2177 Aleuritic acid Free acid from shellac 495.0569 Laccaic B Colorant from lac Summed for PCA 536.0834 Laccaic A Colourant from lac 549.3433 Aleuritic-Laccijalaric Ester from shellac 565.3352 Aleuritic-Jalaric Ester from shellac 791.5315 Jalaric-Aleuritic-Butolic Diester from shellac Summed for PCA 827.4587 Jalaric-Aleuritic-Jalaric Diester from shellac 1113.673 Jalaric-Aleuritic-Aleuritic-Jalaric Triester from shellac 1339.866 Jalaric-Aleuritic-Butolic-Aleuritic-Jalaric Tetraester from shellac 1662.008 Jalaric - Jalaric - Jalaric – Aleuritic- Pentaester from shellac Aleuritic- Aleuritic
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Figure 3 Visible light image of all pigments mock-up samples and their names. Also shown here are alum, an orange shellac and a contemporary industrially made rose madder lake from kremer pigmente.
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4. Results and discussion
As discussed in the last chapter a total of 33 samples was made which will be discussed here divided into two sample groups. The main sample group can be found in Table 3 and contains all the samples which were made by variations in the temperature and pH of extraction. These samples will be the main focus of this discussion and result section as they represent the fundamental experimental parameters in lac production. The other samples which were produced, as shown in Table 4, contain samples that represent variations in different parameters, this group will be discussed separately at the end of this chapter. After discussing some observations which were made during the production of the mock up samples the main sample group will be discussed per analysis technique.
The main sample group contains three direct pigments, eight textile pigments and four textiles (unaged and aged). There originally were supposed to be four direct pigments, but lac colourants will only precipitate on alum under alkaline conditions. When the colourants were extracted under cold and neutral conditions no pigment was obtained, under neutral and hot conditions some pigment precipitated although not in comparison to the pigments precipitated in alkaline conditions. All colourants for dyeing were extracted at neutral pH, dyeing is unsuccessful at a high pH, which gives an indication of the amount of shellac that can possibly be extracted under cold and neutral conditions.
From the sticklac residue after the colourant extraction an initial evaluation of the possible degree of shellac inclusion in the final product can be made. Under cold and neutral conditions the sticklac appears the same after extraction. When heat is applied the residue melts and forms a sticky lump. When the colourants are extracted in alkaline condition at room temperature, some of the shellac appears to dissolve but a residue remains. When alkaline conditions and heat is applied, the sticklac dissolves completely and only a few bits of wood remain after the extraction. The colourants extracted for dyeing appear the same, and result in similarly coloured silks. Some are unevenly dyed which is caused by insufficient stirring, and the silk texture has changed to slightly more rough after dyeing. This could be caused by a shellac coating deposited on the silk fibres. From the textile clippings from which the textile pigments were made a clear distinction can be seen between the hot and cold extraction methods (both under alkaline conditions). When heat is applied the clippings are back to their undyed colour, whereas when the extraction is done at room temperature a pink colour remains on the silk after the extraction. The resulting pigments show a lot more variation in colour than their original textiles, indicating that perhaps the colour saturation of the silk was reached during dyeing. One last interesting observation about the production of these samples is that some parts of the historical recipes are more logical after having reproduced them. Recipes for direct pigments often mention that a clean bowl should be used after extraction to precipitate the pigments in, which is probably related to the melted shellac residues which stick to the vessel after extraction. Imaging A set of multispectral images was made of the pigments and dyed textiles (unaged and aged). The visible light image of the pigments can be found in Figure 3, the other images can be found in Appendix II. These images can provide a lot of insights which can be corroborated by other techniques which will be discussed further on. In the visible light image of the pigments twenty one samples are presented. On the top alum and shellac can be seen and the top left the Indian lac obtained from Kremer Pigmente, this colourant was proven to be pure laccaic acid A and B (not precipitated on a substrate) by FTIR, DAD-ESI-Q-ToF and the fact that it readily dissolves in water.
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Together these three form a reference to determine their individual influence on the mock-up samples. Rose madder lake is included as an example to show the properties of a commonly used lake pigment. There is a lot of difference in colour between the pigments. The most striking difference is between the Kremer pigments and the pigments made during this research. This difference can be attributed to the three pka values of the laccaic acids. From this it can be concluded that the Kremer colourant was produced in an acid environment, and when dissolved in water it becomes a similar shade as other pigments. The difference in colour of the mock-up pigments might be attributed to a number of factors such as: pH, concentration of colourants, inclusion of shellac or other production method related factors. The two direct pigments made in an alkaline environment are darker in colour than the majority of the textile pigments, which are somewhat more pink in tone.
All pigments show a degree of infrared reflectance. Some of the bright pink pigments (TP_C3_C; TP_H1_C; TP_H3_C) show a reflectance similar to the reference Kremer pigment. The darker pigments (DP_C_A; TP_H1_H) show the least reflectance. Note that the reflectance of shellac is difficult to measure because of the flaky characteristics of this sample it is reflecting on its own, non IR induced reflectance. In the UV reflectance image the reference pigment shows no reflectance under UV while alum is highly reflecting (shellac difficult because own reflectance). The darker pigments show no reflectance, they absorb similarly to the reference pigment. The light pink pigment (DP_H_N) shows a higher reflectance, similar to the alum. This shows that UVR is mainly due to the alum present, while reflectance is reduced by a high concentration of pigment which absorbs the UV. The UV luminescence shows that the alum and reference pigment do not luminescence under UV, but the shellac does, indicating that any luminescence in the pigments must come from shellac. The rose madder is very different under UV. Also to be noted is that the 2nd column and 4th column of pigments in Figure 3 luminesce more than the other two. These correspond to the pigments made through a hot extraction, in the case of the textile pigments hot extracted from the silk disregarding the original extraction method of the dye for the silk. This could be an indication for a higher concentration of shellac.
There is little difference to be observed between the textiles in the multispectral images. Inhomogeneity in the dye can be seen throughout the images on most of the samples indicating that the dyebath was not stirred enough. The aged silks show little change in the multispectral images except for a change in colour intensity corresponding to a probable fading and thus degradation of the colourant molecules.
22 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Colourimetry data By using the multispectral images an indication of the colour of the different samples can made. These values are plotted in Figure 4 and only give an indication of the colours present and not the intensity. All samples show values in the positive a* red values and negative b* blue values which is consistent with the purple colour of the pigments and dyed silks. The textiles are close together in their colour values and all show a similar shift upon ageing which can be confirmed by the . This corroborates the observation from the multispectral imaging that there is no large variation between these textiles even though their production method is different. Their resulting pigments∆𝐸𝐸 show a lot more variation than can be seen between the textiles they originate from and the production method. The pigments extracted at room temperature show a shift to the right on the a* axis, indicating more red, compared to the ones extracted at boiling point. HPLC - DAD The results from the HPLC-DAD measurements were collected at 491 nm and normalised to their sample weight and dilution. Due to the two different types of samples, pigments and textiles, the DAD signal intensities of the pigments and textiles need to be considered separately. The signal for the combined peak of Laccaic Acid A and Laccaic Acid B was taken as these molecules give the largest contribution to the colourant matrix and have an overlapping spectrum. The linear relationship between the concentration and the signal intensity allows for this to be taken as a relative quantification of colourant concentrations between the different samples. The HPLC-DAD- MS system was not optimised for DAD measurements which can be noted in the absence of signal for the samples TP_C1_H and TP_H3_H.
The direct pigments show a large difference in signal intensity, as can be seen in Figure 5. The pigment with the highest concentration appears to be the direct pigment made at alkaline (pH 11) and cold (room temperature) conditions (DP_C_A). The signal is 28 times greater than the signal for the direct pigment made at neutral cold conditions (DP_H_N), and 3 times greater than the signal made at hot (100°C) alkaline conditions (DP_H_A). From this it can be deducted that the most important factor determining the final concentration of colourants is the alkalinity of the extraction solution. The resinous components start to dissolve at a pH of around 8 but apparently this is not the only factor influencing the solubility of shellac. Due to the cold conditions used to create pigment DP_C_A, the amount of resinous components dissolved is limited compared to the conditions of DP_H_A. However complete dissolution is obtained only when high temperatures are used. This
180 140 160 120 140
120 100 100 80 80 60
Signal (mAU) 60 Signal (mAU) 40 40 20 20 0 0 Tu_C1 Tu_C3 Tu_H1 Tu_H3 Sample Sample Figure 4 The colourimetry data for the pigments on the left and the textiles on the right. In red are the direct pigments, blue the textile pigments, yellow the unaged textiles and green the aged textiles. Figure 5 HPLC-DAD results for the peak area of the pigment samples on the left and the textile samples on the right 23 Berbers, Uva 2018 Lac sources in Hellenistic pigments
shows that all of the resinous components were dissolved in the extraction process and possibly incorporated into the final pigment. A result of this might be that the final concentration of colourant molecules per mg of pigment is lower due to the high amount of resinous components.
This is corroborated by the full colour images of the pigments (Figure 3) and the plotted colourimetry values, DP_C_A can be considered as the pigment with the most intense colour. The DAD results indicate that the colour intensity can be attributed to a great extent to the high amount of colourant that is extracted when the polymer network of shellac is broken down due to the high pH. The DP_H_A shows a smaller amount of colourant molecules, even though the sticklac was completely dissolved after the extraction. Indicating that not all of the colourant molecules were precipitated on the pigment, perhaps the dissolved shellac created a more favourable environment for the colourant molecules to stay in solution.
The pigments extracted from textiles show a similar or lower DAD signal than DP_H_A. Tp_C3_C has the highest signal, and corresponds to the brightest colour of the textile pigments. There appears to be a discrepancy for the pigment TP_H1_H, which has a low signal intensity for the DAD but appears very dark in colour. Textile pigments are all extracted at alkaline conditions, higher concentrations seem to be obtained when the temperature is not raised. Although the samples are normalised according to the sample size, it is difficult to compare the concentration of the direct pigments with the textile pigments, as the concentration of the latter is dependent on the amount of textile clippings used and the concentration of colourants on the textile.
Although visually little difference could be seen between the dyed textiles, significant
differences can be seen through the DAD results. The Tu_H3 has a signal intensity almost four times
higher than Tu_C3, which is the textile with the apparent lowest colourant concentration. The textiles were not dyed under alkaline conditions, an attempt at this was done but this did not result in a successful dyeing. The textiles which were dyed with hot extracted colourants show the highest concentrations of colourants. There is no comparison available for a pigment made in neutral and cold extraction conditions as this did not result in a successful pigment. The multiple dyeing process seems to have a positive effect on the colourant concentration only in the case of the hot extracted pigments. It could be that the amount of colourant molecules extracted by the cold extraction was not high enough to produce a significant increase in concentration on the textile. There is no consistency to be seen between the textile with the highest concentration of colourants and the pigments extracted from the same textiles. The textile with the lowest signal intensity for the colourant molecules resulted in the pigments with the highest signal intensity. HPLC-ESI-Q-ToF As described in the previous chapter, in view of the high number of different molecular components, samples and the variety within the samples, Principle Component Analysis (PCA) was used to identify and highlight similarities and differences between the samples and sample groups, in correlation with the variables using the data obtained through the analysis of the MS spectra. A list of these components and their molecular masses can be found in Table 5. The complete dataset per sample can be found in Table 6 for the textile samples and Table 7 for all the pigment samples.
The score plot for the PC1 and PC2 can be found in Figure 6 and accounts for 71.31% of the total variance. The contributions of the different variables across these PC’s can be found in Figure 7. The score plot for PC1 and PC3 can be found in Figure 8, accounting for 57.40% of the total variance, the variables across the PC in Figure 9. In PC1 the variables giving a positive loading are all the free and (poly)-esters except for butolic acid. Both the lac and the shellac colourants and the butolic acid have a negative loading for PC1. In PC2 only the two esters aleurtic-laccijalaric and aleuritic-jalaric
24 Berbers, Uva 2018 Lac sources in Hellenistic pigments
have a negative loading, all other components have a positive loading. PC3 has a negative loading for the free acids butolic acid, aleurtic acid, and the aleuritic-jalaric ester, and positive loadings for all the rest of the variables. In the PCA plot the samples are coloured according to the type of samples grouped in: i) direct pigments; ii) textile pigments; iii) unaged textiles; iiii) aged textiles. There are three groups that can be distinguished on the score plot: the textile pigments; the textiles dyed with colourants extracted at room temperature and the textiles dyed with colourants extracted at boiling point.
For the direct pigments a large spread through the score plot can be seen. This can be attributed to the larger variation in production method compared to the other samples. All three direct pigments have a positive loading PC1, the highest for DP_H_A and smallest for DP_H_N. This indicates DP_H_A has the largest contribution of shellac components compared to all other samples. The negative correlation of the colourant molecules and butolic acid could be caused by the total possible theoretical amount of colourants molecules which contributes to maximally 8% of the total composition of sticklac and account for two variables in the PCA, compared to up to 87% for shellac components and eight PCA variables. If all the colourant molecules are incorporated into the pigment, the contribution of shellac could quickly become more important due to the high relative amount present in the sticklac and the larger number of different components. The large distance on the score plot between DP_C_A; DP_H_N and DP_H_A pigments indicates that the combination of both heat and alkalinity is needed to fully incorporate the shellac components into the pigment matrix. When looking at the second PC for DP_H_A there is a negative correlation for the esters, but a positive correlation for all the free acids and polyesters. The situation is reversed for the other two direct pigments. This suggests that the high pH and alkalinity break down the polymer network so the larger polyesters are released but simultaneously causes a breakdown of the mono esters into free fatty acids.
The dyed textile samples seem to be divided on the PCA score plot into two groups with the distinction originating from the colourant extraction temperature. The textiles dyed with colourants extracted at boiling point lie close on the score plot to DP_H_N which has identical extraction conditions, and indicated a positive correlation for the less water-soluble compounds which can be expected when the higher temperature increases the solvability of compounds. The textiles dyed with colourants extracted at room temperature have a negative correlation with the colorant molecules and butolic acid. This is interesting as these are the water soluble compounds which should have a positive correlation as they are the compounds most likely to be extracted at these conditions. The relative amounts of compounds extracted at these mild extraction conditions might cause this unexpected result, the water soluble compounds only make up a small percentage compared to the total sticklac composition. For PC2 both the textiles groups have the same negative correlation on the score plot, which can be connected to the mono esters. From the PCA its seems that there is often a distinction between the mono-esters and the free acids and polyesters, possibly to do with a dissociation rate where the polyesters turn in to mono esters which turn into free acids.
The pigments made from textiles are clearly distinguishable from the other samples in the score plot describing PC1 and PC2 (Figure 6). They have a negative loading for PC1, which can be associated to the water soluble compounds. Due to the multiple extraction steps that take place in water before the final pigment is obtained it could be imaginable that some of the water-soluble components are lost. For PC2 there is a positive loading, indicating a degradation of the monoesters. The score plot with PC1 and PC3 is more interesting for the textile pigments, as a clear distinction can be seen between the pigments originating from the textiles dyed with colourants extracted at room temperature, and those extracted from textiles dyed with colourants extracted at boiling point
25 Berbers, Uva 2018 Lac sources in Hellenistic pigments
(Figure 8). The textiles they originate from are close to the pigments on the score plot in both instances, but shifted to the right.
When looking at the complete data set other things can be noted about the samples. Laccijalaric acid is only present in the pigments and in the textiles dyed with colorants extracted boiling point, and is not detected in any of the textile pigments. The aleuritic-jalaric ester is the only ester (and polyester) that can consistently be found in all the textile pigments, indicating its durability against degradation under heating and high pH. There is also an interesting observation to be made about the free acids, laccijalaric acid and jalaric acid, which are only present in the textiles dyed with colourants extracted at boiling point and not in any of the textile pigments. The free acids butolic acid and aleuritic acids can be found in all of the samples. The textiles dyed with colourants extracted at boiling point contain a considerable higher amount of polyesters than ones dyed with colourants at room temperature which only contain monoesters. One of the markers for tannins, ellagic acid, was found in the direct pigments, and in all of the unaged textiles (not in the aged textiles). This indicates that the wood residue present in the sticklac indeed contributes some tannins to the colourant matrix.
26 Berbers, Uva 2018 Lac sources in Hellenistic pigments
4
3 DP_H_A TP_H3_H 2 TP_H1_H
TP_C1_C TP_H1_C 1 TP_C3_H TP_C1_H TP_H3_C TP_C3_C 0
PC2 (26.19 %) Tu_C3 Tu_C1
-1 Ta_C1 Tu_H3 Tu_H1 Ta_C3 DP_C_A Ta_H3 -2 Ta_H1
DP_H_N -3 -4 -2 0 2 4 6 8 PC1 (45.12 %)
1 Figure 6 PCA score plot of the first and second loading Aleuritic acid 0,75 Butolic acid Jalaric acid 0,5 Lac Laccijalaric colourants acid 0,25 Polyesters Shellac colourants 0
PC2 (26.19 %) -0,25
-0,5 Al-Lac -0,75 Al-Jal
-1 Figure 7 Variables for PC1 and PC2 -1 -0,75 -0,5 -0,25 0 0,25 0,5 0,75 1 PC1 (45.12 %)
27 Berbers, Uva 2018 Lac sources in Hellenistic pigments
28 Berbers, Uva 2018 Lac sources in Hellenistic pigments
2 TP_C3_H 1,5 TP_C3_C Tu_C3 DP_H_A 1 DP_C_A TP_C1_C Tu_C1 Ta_C3 0,5 Ta_C1 Tu_H1 TP_C1_H 0
TP_H1_C Tu_H3 -0,5 DP_H_N Ta_H1
PC3 (12.28 %) -1 TP_H1_H Ta_H3 -1,5 TP_H3_C
-2 TP_H3_H -2,5
-3 -4 -2 0 2 4 6 8 PC1 (45.12 %)
Figure 8 PCA score plot of the first and third loading 1
0,75 Shellac colourants
0,5 Lac colourants
Jalaric acid 0,25 Al-Lac Polyesters Laccijalaric 0 acid
-0,25 PC3 (12.28 %) Aleuritic acid Al-Jal -0,5 Butolic acid
-0,75
-1 -1 -0,75 -0,5 -0,25 0 0,25 0,5 0,75 1 PC1 (45.12 %) Figure 9 Variables for PC1 and PC3
SEM
Fibres of undyed silk, dyed silk (Tu_C1; Tu_H1) and the same silk after colourant extraction (TP_C1_H; TP_C1_C; TP_H1_H; TP_H1_C) were examined using scanning electron microscopy (SEM). These samples were chosen because they represent both hot and room temperature extractions for the dyeing and extraction steps. The magnification and resolution provided by SEM enables an evaluation of the fibre condition. The textile fibres were examined at different degrees of magnification, the resulting images can be found in Appendix IV. The high pH and temperatures applied during the extraction process have been known to result in fibre degradation and protein
29 Berbers, Uva 2018 Lac sources in Hellenistic pigments
residues have been identified in such pigments.6 There is no apparent change or degradation visible in any of the samples. It should be noted that wool is known to be more susceptible to degradation under these colourant extraction conditions than silk but this lies outside the scope of this research.
FTIR The FTIR spectrum obtained from the Kremer Pigmente Indian lac pigment did not show evidence of the presence a lake substrate or the presence of resinous shellac components.6 From reference spectra available in the FTIR reference database of the British museum the sole presence of Laccaic Acid A and B could be confirmed. The direct pigment samples show characteristic bands for shellac, but the bands characteristic of laccaic acid a and b could not be discerned because of the high intensity shellac bands. A peak at 1560 cm-1 is the most distinguishable difference between the known spectrum of shellac and the measured lac lake, which might be attributed to the amorphous aluminium hydroxide lake substrate. [ref vibrational and electronic properties of paintings lakes] The dyed silks showed no indication in the spectra of the presence of lac colourants or shellac components due to the high intensity peaks of the silk proteins in the region 1700-800 cm-1 where the characteristic peaks for the colourant molecules and shellac molecules are also based. The extraction of dyestuff from the silk did not have an effect on the FTIR spectrum of the silk. The spectrum produced by the textile pigments provides little information and only features a couple of broad peaks, this could indicate that the samples contained to much water at the time of the measurements and no conclusions can be drawn from the spectra. Aging The textile samples were artificially aged for one month after which they were analysed by multispectral imaging and HPLC-DAD-ESI-Q-ToF. The results have been included in the PCA plots as shown in Figure 6 and 8. The PCA plots do not indicate a large difference between the aged and the unaged samples, they remain in the same area of the PCA plot as their unaged counterparts. When looking at the DAD results a significant decrease in signal intensity for the Laccaic Acids A and B can be seen. It is difficult to determine from these results if there is a difference in degradation between the colourant molecules and the shellac components as there are no quantitative measurements for the shellac components. However if degradation of shellac components had occurred it would be expected to find a change in the poly- ester compositions as these degrade to free acids. This being not the case it is likely only the colourant molecules have degraded and not the shellac components. It is also clear from the HPLC-DAD-ESI-Q-ToF data that the Ellagic acid , a tannin in this case originating from wood contamination in the sticklac, only remained detectable in one aged sample. Indicating the sensitivity of Ellagic acid to aging. Addition samples The samples described in Table 4 have not yet been discussed, they represent samples which lie slightly outside the main scope of the research. The parameters involved are for example the effect of urine as a source of an alkaline solution and the susceptibility of silk for the shellac components. All these samples will be individually briefly discussed in this section.
The two additional direct pigments which were made are DP_H_U and DP_U_A_T. The first pigment was made by using an alkaline solution of 20 day old urine, and boiled to reduce to halve the volume as an alkaline solution, this was taken from the historical recipe §130 from the Bolognese Manuscript.51 The historical recipes for almost all lac pigments use urine as a source of alkalinity, either direct or by making ley from urine. Urine is a complex mixture of human waste products, and this pigment was made to investigate if this has an influence on the resulting pigment.
30 Berbers, Uva 2018 Lac sources in Hellenistic pigments
The pre-treatment of the urine resulted in a significant darkening, although more care during the urine reduction might have limited this effect slightly. This is already an influential on its own, compared to the analytical grade colourless solutions used in the other mock-up samples. The resulting pH was around 8.5, making a ley from urine would have resulted in a pH of around 11 but this was outside the scope of this research. As expected the resulting pigment is one of the darkest pigments, but lower in colourant concentration than DP_H_A and DP_C_A. When looking at the MS results, and the PCA with all samples included (Appendix V) it can be noted that the pigment is similar to the DP_H_N. This indicates that a higher pH is needed to fully dissolve the sticklac polymer network. The DP_H_A_T was made after the unsuccessful dyeing at a pH of 11 and a hot colorant extraction. The solution was kept as a dye bath at 70 °C for an hour with silk, afterwards alum was added to a small fraction of the solution resulting in the pigment. The concentration of colourants as shown by the DAD results is very low, similar to the DP_H_N pigment. When looking at the PCA plot it is clear that this pigment is very different from the other pigments, but similar to the textile after the unsuccessful dyeing. This could be the result of the much more extended heating of the colourant solution compared to the other pigments. The pigment and the textile are very close to each other on the PCA plot and this can indicate that the molecular composition is very similar.
The textiles and resulting extracted textile pigments that have not yet been discussed are
Tu_H3.1, Tu_H3.2, Tu_H3.3. These investigate the difference in affinity of the silk for the colourant molecules and the shellac components by consecutively dyeing three pieces of silk in the same dye bath. From the multispectral images it can be seen that there is a significant decrease in colour intensity on the silk dyed secondly, the thirdly dyed silk was not included in the image set and not further studied as it showed almost no colour. The Tu_H3.2 looks similar to the undyed silk, both the IIR and the UVR appears more yellow (although these are false colour images, so the yellow indicates a difference in reflectance not actual colour) which indicates there is something on the silk compared to the undyed silk. This is further revealed in the UVL images, where silk Tu_H3.2 is considerably less luminescing than the undyed silk. This could be caused by the small amount of lac colourants present, which from the pigment images are known to absorb UV, as the presence of shellac components should increase the luminescence. The silk in these images looks remarkably
similar to the corresponding pigments. When looking at the two pigments made from Tu_H3.2, they show the highest luminescence, which appears to look similar to the textile Tu_H3.2. Analysis by
HPLC-DAD-ESI-Q-ToF showed that textile Tu_H3.2 showed half the signal intensity as textile dyed in
the first dyebath, Tu_H3.1. There was no change apparent in the type of shellac components between the two textiles and they close together on the PCA plot as can be seen in Appendix V. This indicates that there is no competition between shellac components and the colourant molecules on the silk. There are no shellac components which have more affinity to the silk, if this would have been the case they would have been extracted from the dye bath by the first silk and the molecular composition of the secondly dyed silk would not be similar to the first. The pigments resulting from
textile Tu_H3.2 are slightly different than the other textile pigments, for the hot extracted pigment Laccaic Acid B was not detected, only laccaic acid A. The second PCA plot shows these pigments as outliers, which is connected to a negative correlation for butolic acid.
31 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Table 6 Complete dataset for the HPLC-DAD-ESI-Q-ToF data of all textile samples
M/z Generic Tu_C1 Tu_C3 Tu_H1 Tu_H3 Tu_H3 Tu_H3 Ta_C1 Ta_C3 Ta_H1 Ta_H3 Ta_H3 Ta_H3 average name .1 .2 .1 .2 std 243.19 Butolic 14.23 11.80 16.39 8.26 12.71 8.28 17.07 15.53 11.97 11.30 14.75 13.55 0.40 96 acid 263.12 Laccijal - - 0.26 0.32 0.31 0.57 - - 0.31 0.40 0.38 0.97 0.01 98 aric acid 269.04 Deoxye 0.77 0.85 0.35 0.14 0.26 0.12 0.81 1.45 0.16 0.10 0.17 - 0.07 55 rythrola ccin 279.12 Jalaric - - - 0.24 0.18 0.41 - - - 0.26 0.18 0.64 0.02 38 acid 285.04 Erythrol 1.55 2.40 0.66 0.35 0.43 0.26 1.99 3.82 0.32 0.23 0.36 - 0.08 05 accin 300.99 Ellagic 0.05 0.12 0.07 0.13 0.26 0.15 - - - - 0.14 - 0.01 acid 303.21 Aleuriti 0.62 0.44 1.11 1.26 1.46 2.41 1.25 2.03 3.03 3.32 2.88 5.20 0.12 77 c acid 495.05 Laccaic 18.36 21.18 4.18 10.85 11.21 4.76 15.25 10.34 3.62 1.69 3.51 0.40 0.13 69 B 536.08 Laccaic 37.67 39.56 7.29 20.39 20.44 9.18 32.08 20.58 7.28 3.57 6.76 0.76 0.28 34 A 549.34 Al-Lac 10.42 9.93 16.34 5.88 7.80 8.20 12.65 20.43 8.14 6.62 8.14 4.65 0.14 33 565.33 Al-Jal 16.34 13.57 35.80 51.24 44.94 64.56 18.88 25.82 64.76 71.75 62.31 73.84 0.23 52 791.53 Jal-Al- - - 2.64 0.06 ------0.08 15 But 827.45 Jal-Al- - - 1.04 0.38 - - - - 0.41 0.37 0.42 - 0.02 87 Jal
1113.6 Jal-Al- - 0.14 10.69 0.50 - 1.10 - - - 0.39 - - 0.24 73 Al-Jal 1339.8 Jal-Al- - - 0.51 ------0.03 66 But-Al- Jal 1662.0 Jal-Jal- - - 2.66 ------0.08 08 Jal-Al- Al-Al DAD Laccaic 49.1 32.2 65.3 130.5 57.73 29.73 35.6 11.1 35.6 16.7 30.23 - 4.23 491 nm B and A
32 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Table 7 Complete dataset for the HPLC-DAD-ESI-Q-ToF data of all pigment samples
M/z Generic DP_ DP_ DP_ DP_ DP_ TP_C TP_C TP_C TP_C TP_ TP_ TP_ TP_ TP_ TP_ TP_ TP_ Average name H_N C_A H_A H_A H_U 1_C 1_H 3_C 3_H H1_ H1_ H3_ H3_ H3.1 H3.1 H3.2 H3.2 std _T C H C H _C _H _C _H 243.1996 Butolic 12.0 13.0 10.3 12.2 16.0 25.4 41.4 12.5 20.1 24.8 41.4 38.1 53.1 48.8 37.5 60.5 80.6 0.40 acid 0 4 7 7 5 2 0 9 1 7 3 9 4 3 5 4 3 263.1298 Laccijalar 0.09 0.55 3.26 6.57 0.12 ------0.01 ic acid 269.0455 Deoxyer 0.16 0.89 0.46 0.22 0.13 3.25 3.44 1.96 2.41 - 1.23 ------0.07 ythrolacc in 279.1238 Jalaric 0.03 0.57 3.85 10.8 0.04 ------0.02 acid 7 285.0405 Erythrola 0.30 1.66 0.56 0.49 0.38 3.11 6.59 4.14 7.16 - 1.66 ------ccin 300.99 Ellagic 0.07 0.07 0.05 0.00 0.09 ------0.01 acid 303.2177 Aleuritic 0.27 1.52 14.7 35.2 0.47 3.66 3.68 1.43 1.76 5.06 3.80 5.89 8.41 3.22 3.60 6.46 3.43 0.12 acid 2 4 495.0569 Laccaic B 0.86 2.13 0.52 0.77 2.34 16.5 8.16 22.9 18.9 19.8 16.9 8.31 13.1 10.6 18.1 - - 0.13 2 3 8 6 0 4 4 7 536.0834 Laccaic A 1.92 4.73 1.03 1.54 4.80 45.8 19.1 56.2 42.0 47.7 33.1 19.2 25.3 26.1 35.0 33.0 3.98 0.28 0 8 2 2 7 3 4 1 2 6 0 549.3433 Al-Lac 17.3 23.2 11.5 2.63 18.3 ------5.71 - 8.28 5.63 - 3.48 0.14 6 4 7 9 565.3352 Al-Jal 62.8 29.2 25.8 19.8 49.2 2.25 17.5 0.73 7.56 2.45 1.85 17.3 - 2.91 - - 8.48 0.23 8 2 1 8 3 4 2 791.5315 Jal-Al- 0.14 4.74 4.22 1.94 0.67 ------5.35 - - - - - 0.08 But 827.4587 Jal-Al-Jal 0.68 0.66 6.06 1.91 0.54 ------0.02
1113.673 Jal-Al-Al- 3.24 13.4 13.5 4.51 6.00 ------0.24 Jal 0 3 1339.866 Jal-Al- - 0.81 0.73 0.30 0.06 ------0.03 But-Al- Jal 1662.008 Jal-Jal- - 2.77 3.26 0.86 0.69 ------0.08 Jal-Al-Al- Al DAD 491 Laccaic B 5.9 164. 54.8 6.88 18.7 32.1 - 49.2 15.3 14.9 5.2 13.1 - - - - - 4.23 nm and A 8 6
33 Berbers, Uva 2018 Lac sources in Hellenistic pigments
5. Concluding remarks
This research has aimed to investigate historical formulations of lac lake pigments and dyes by studying the compositional variability. In order to asses this three different steps were undertaken: i) studying historical recipes, ii) making mock-up samples, iii) technical examination of the mock-up samples. This resulted in the identification of the most important parameters in the production process of lac lake pigments and dyes: pH and temperature. The technical examination of the mock- up samples resulted in the conclusion that even if these parameters are very mild, inclusion of shellac components into the colorant matrix is unavoidable unless more refined chemical techniques are used which are not described in any of the historical recipes. The type of shellac components that are transferred to the resulting pigment or dyed textile is dependent on the production method and can vary greatly dependent on the experimental parameters. As expected due to the numerous steps in the production, the pigments made by the extraction of colourants from a lac dyed textile showed the least variety in shellac components. From this it can be concluded that until the industrial revolution and more refined production methods came into practice, shellac components can be expected to be found together with lac colourants.
For restoration practices and historical research into dyes and pigments this knowledge might aid the future detection of lac. It corroborates the conclusions made by Dyer et al when they identified lac on a Hellenistic terracotta oinochoe due to the presence of shellac components.1 Essential in this was the use of mass spectrometry for means of detection as it allowed the detection of the non-coloured shellac components. Due to the use of shellac historically and in conservation practice care must always be taken to exclude this before contributing the presence of shellac components to a lac pigment or dye.
The scope of this research was limited in terms of parameter variability and textile substrate. A future study could asses the effects of a more moderate alkaline pH, and moderate temperature being used during the extraction of colourants. It would be interesting to investigate if there is a difference in affinity of shellac components for wool compared to silk when dyeing with lac. A start was made to study the effect of aging on the degradation of the different colourant and shellac components. Continuing this also with pigments in different binding media would provide interesting insights into both the working properties of lac pigments (direct and extracted from textiles), and the possible difference in degradation between the colourant and shellac components.
6. Acknowledgements Working at British Museum has been an amazing experience, and I would like to thank the whole scientific research department for helping me and involving me in their work. Specifically Joanne Dyer and Diego Tamburini for their supervision and guidance during this project. Furthermore I would like to thank professor M. van Bommel for all the fruitful discussions about this research and the supervision given by him through the University of Amsterdam.
34 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Bibliography
(1) Dyer, J.; Tamburini, D.; Sotiropoulou, S. The Identification of Lac as a Pigment in Ancient Greek Polychromy - The Case of a Hellenistic Oinochoe from Canosa Di Puglia. Dye. Pigment. 2017, 149, 122–132. (2) Wouters, J.; Verhecken, A. The Coccid Insect Dyes : HPLC and Computerized Diode-Array Analysis of Dyed Yarns Author ( s ): Jan Wouters and André Verhecken Source : Studies in Conservation , Vol . 34 , No . 4 ( Nov ., 1989 ), Pp . 189-200 Published by : Taylor & Francis , Ltd . on B. Stud. Conserv. 1989, 34 (4), 189–200. (3) Brown, K. S. The Chemistry of Aphids and Scale Insects. Chem. Soc. Rev. 1975, No. 4, 263–288. (4) Wadia, M. S.; Khurana, R. G.; Mhaskar, V. V; Dev, S. The Chemistry Lac Resin - I: Lac Acids (Part 1): Butolic, Jalaric and Laksholic Acids Nsects. Tetrahedron 1969, No. 25, 3841–3853. (5) Castro, R.; Miranda, A.; Melo, M. J. Interpreting Lac Dye in Medieval Written Sources : New Knowledge from the Reconstruction of Recipes Relating to Illuminations in Portuguese Manuscripts. 2015, 1918 (October), 88–99. (6) Kirby, J.; Spring, M.; Higgitt, C. The Technology of Red Lake Pigment Manufacture: Study of the Dyestuff Substrate. Natl. Gall. Tech. Bull. 2005, 26, 71–87. (7) Jeammette, V.; Knecht, C.; Pages-Camagna, S. The Polychrome Decoration on Hellenistic Terracottas : Figurines from Tanagra and Myrina in the Collection of the Musee Du Louvre. In Tanagras: Figurines for life and eternity; Valencia: Fundacion Bancaja, 2010; pp 245–249. (8) Santos, R.; Hallett, J.; Oliveira, M. C.; Sousa, M. M.; Sarraguça, J.; Simmonds, M. S. J.; Nesbitt, M. HPLC-DAD-MS Analysis of Colorant and Resinous Components of Lac-Dye: A Comparison between Kerria and Paratachardina Genera. Dye. Pigment. 2015, 118, 129–136. (9) Burwood, R.; Read, G.; Schofield, K. The Pigments of Stick Lac. Part II. The Structure of Laccaic Acid A. J. Chem. Soc. 1967, 842–851. (10) Castro, R.; Pozzi, F.; Leona, M.; Melo, M. J. Combining SERS and Microspectrofluorimetry with Historically Accurate Reconstructions for the Characterization of Lac Dye Paints in Medieval Manuscript Illuminations. J. Raman Spectrosc. 2014, 45 (11–12), 1172–1179. (11) Constable, O. R. Trade and Traders in Muslim Spain: The Commercial Realignment of the Iberian Peninsula, 900-1500; Cambridge University Press: Cambridge, 1994. (12) Roy, M. Dyes in Ancient and Medieval India.Pdf. 1977, 13 (2). (13) Pliny. Naturalis Historica. (14) Warmington, E. H. The Commerce between the Roman Empire and India; Cambridge University Press , 1928. (15) Scholfield, A. F. Aelian On the Nature of Animals. In I; William Heinemann and Harvard university press: London, Cambridge Massachusetts, 1958; pp 266–267. (16) Martelli, M. Alchemical Textiles: Colourful Garments, Recipes and Dyeing Techniques in Graeco-Roman Egypt. In Greek and Roman textiles and dress: an interdisciplinary anthology; Harlow, M., Nosch, M. L., Eds.; Oxbow, 2014; pp 111–129. (17) Rosenberg, E. Characterisation of Historical Organic Dyestuffs by Liquid Chromatography- Mass Spectrometry. Anal. Bioanal. Chem. 2008, 391 (1), 33–57.
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(18) Wouters, J. Dye Analysis in a Broad Perspective: A Study of 3rd- to 10th-Century Coptic Textiles from Belgian Private Collections. Dye. Hist. Archaeol. 1994, 13, 38–45. (19) Wouters, J. High Performance Liquid Chromatography of Anthraquinones: Analysis of Plant and Insect Extracts and Dyed Textiles. Stud. Conserv. 1985, 3, 119–128. (20) Zhang, X.; Laursen, R. A. Development of Mild Extraction Methods for the Analysis of Natural Dyes in Textiles of Historical Interest Using LC-Diode Array Detector-MS. Anal. Chem. 2005, 77 (7), 2022–2025. (21) Valianou, L.; Karapanagiotis, I.; Chryssoulakis, Y. Comparison of Extraction Methods for the Analysis of Natural Dyes in Historical Textiles by High-Performance Liquid Chromatography. Anal. Bioanal. Chem. 2009, 395 (7), 2175–2189. (22) Kirby, J.; van Bommel, M.; Verhecken, A. Natural Colorants for Dyeing and Lake Pigments Practical Recipes and Their Historical Sources; Archtype Publications Ltd, 2014. (23) Lech, K.; Jarosz, M. Novel Methodology for the Extraction and Identification of Natural Dyestuffs in Historical Textiles by HPLC – UV – Vis – ESI MS. Case Study : Chasubles from the Wawel Cathedral Collection. Anal. Bioanal. Chem. 2011, 399, 3241–3251. (24) Marques, R.; Sousa, M. M.; Oliveira, M. C.; Melo, M. J. Characterization of Weld (Reseda Luteola L.) and Spurge Flax (Daphne Gnidium L.) by High-Performance Liquid Chromatography-Diode Array Detection-Mass Spectrometry in Arraiolos Historical Textiles. J. Chromatogr. A 2009, 1216 (9), 1395–1402. (25) Gulmini, M.; Idone, A.; Davit, P.; Moi, M.; Carrillo, M.; Ricci, C.; Bello, F. D.; Borla, M.; Oliva, C.; Greco, C.; et al. The “Coptic” Textiles of the “Museo Egizio” in Torino (Italy): A Focus on Dyes through a Multi-Technique Approach. Archaeol. Anthropol. Sci. 2017, 9 (4), 485–497. (26) Pfisters, R. Teinture et Alchimie Dans l’Orient Hellénistiqueitle. Semin. Kondakovianum 1935, 7 (VII), 1–59. (27) Eastwood, G. M. Egyptian Dyes and Colours. Dye. Hist. Archaeol. Text. 1984, 3, 9–19. (28) Trojanowicz, M.; Orska-Gawryœ, J.; Surowiec, I.; Szostek, B.; Urbaniak-Walczak, K.; Kehl, J.; Wróbel, M. Chromatographic Investigation of Dyes Extracted from Coptic Textiles from the National Museum in Warsaw. (29) Karapanagiotis, I.; Karadag, R. Dyes in Post-Byzantine and Ottoman Textiles: A Comparative HPLC Study. Mediterr. Archaeol. Archaeom. 2015, 15 (1), 1–13. (30) Petroviciu, I.; Albu, F.; Cretu, I.; Virgolici, M.; Medvedovici, A. Investigation of Natural Dyes in 15th c. Documents Seal Threads from the Romanian Academy Library, by LC-DAD-MS (Triple Quadrupole). J. Cult. Herit. 2017, 1296–2074. (31) Petroviciu, I.; Vanden Berghe, I.; Cretu, I.; Albu, F.; Medvedovici, A. Identification of Natural Dyes in Historical Textiles from Romanian Collections by LC-DAD and LC-MS (Single Stage and Tandem MS). J. Cult. Herit. 2012, 13 (1), 89–97. (32) Gleba, M.; Berghe, I. Vanden; Aldenderfer, M. Textile Technology in Nepal in the 5th-7th Centuries CE : The Case of Samdzong. Sci. Technol. Archaeol. Res. 2016, 2 (1), 25–35. (33) Melo, M. J.; Claro, A. Bright Light: Microspectrofluorimetry for the Characterization of Lake Pigments and Dyes in Works of Art. Acc. Chem. Res. 2010, 43 (6), 857–866. (34) Donkin, R. A. Spanish Red: An Ethnogeographical Study of Cochineal and the Opuntia Cactus; 1977; Vol. 67.
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(35) Donkin, R. A. The Insect Dyes of Western and West-Central Asia Insect Dyes of Western and West-Central Asia. Arthropos 1977, 72 (1977), 847–880. (36) Lluveras-Tenorio, A.; Parlanti, F.; Degano, I.; Lorenzetti, G.; Demosthenous, D.; Colombini, M. P.; Rasmussen, K. L. Spectroscopic and Mass Spectrometric Approach to Define the Cyprus Orthodox Icon Tradition - The First Known Occurrence of Indian Lac in Greece/Europe. Microchem. J. 2017, 131, 112–119. (37) Forbes, R. J. Studies in Ancient Technology Volume IV: Dyes and Dyeing; Leiden, 1956. (38) Cardon, D. Natural Dyes, Sources, Tradition, Technology and Science; Archtype Publications Ltd, 2007. (39) Edelstein, S.; Borghetty, H. C. The Plictho of Gioanventura Rosetti Instructions in the Art of the Dyers Which Teaches the Dyeing of Woolen Cloths, Linens, Cottons, and Silk by the Great Art as Well as by the Common Translation of the First Edition of 1548; The M.I.T. Press, 1969. (40) Thompson Jr., D. V. The Craftsman’s Handbook “Il Libro Dell’Arte” Cennino d’Andrea Cennini, 2014 repri.; Dover Publications: New York, 1933. (41) Partridge, W. A Practical Treatise on Dying Woolen, Cotton, and Silk; Published by the author: New York, 1834. (42) Jessup, D. A. The Effect of P H on the Photochemical Decom-. 1927, 5, 745–749. (43) Bechtold, T.; Mussak, R. Handbook of Natural Colorants; 2009. (44) Limmatvapirat, S.; Limmatvapirat, C.; Puttipipatkhachorn, S.; Nuntanid, J.; Luangtana-anan, M. Enhanced Enteric Properties and Stability of Shellac Films through Composite Salts Formation. Eur. J. Pharm. adn Biopharmaceautics 2007, 67, 690–698. (45) Farag, Y.; Leopold, C. S. Physicochemical Properties of Various Shellac Types. Dissolution Technol. 2009, 33–39. (46) Hacke, M. Weighted Silk: History, Analysis and Conservation. Stud. Conserv. 2008, 9, 3–15. (47) Schweppe, H. Handbuch Der Naturfarbstoffe: Vorkommen, Verwendung, Nachweis; Ecomed, 1993. (48) Dyer, J.; Verri, G.; Cupitt, J. Multispectral Imaging in Reflectance and Photo-Induced Luminescence Modes: A User Manual; Charisma, 2013. (49) Tamburini, D.; Dyer, J.; Bonaduce, I. The Characterisation of Shellac Resin by Flow Injection and Liquid Chromatography Coupled with Electrospray Ionisation and Mass Spectrometry. Sci. Rep. 2017, 7 (1), 1–15. (50) Harris, D. C. Quantitative Chemical Analysis, 8th ed.; W. H. Freeman and Company: New York, 2010. (51) Mrs Merrifield, M. P. Original Treatises in the Arts of Painting, Dating from the XIIth to XVIIIth Centuries; John Murray, Albemarle street: London, 1849. (52) Levey. Mediaeval Arabic Bookmaking and Its Relation to Early Chemistry and Pharmacology. 1962, 121 (1), 46–69. (53) Smith, C. S.; Hawthorne, J. G. Mappae Clavicula a Little Key to the World of Medieval Techniques. Trans. Am. Philos. Soc. 1974, 64 (4). (54) Hilts, P. The Weavers Art Revealed: Facsimile, Translation, and Study of the First Two
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Published Books on Weaving : Marx Ziegler’s Weber Kunst Und Bild Buch (1677) and Nathaniel Lumscher’s Neu Eingerichtetes Weber Kunst Und Bild Buch (1708); Charles Babbage Research Centre, 1990. (55) Clothroads.com natural dyes lac https://www.clothroads.com/natural-dyes-lac/ (accessed Oct 22, 2017). (56) Hellot, M.; Macquer, M.; Le Pileur D’Apligny, M. The Art of Dying Wool, Silk and Cotton, Translation from the French; Printed for R. Baldwin, Rather-Noster-Row: London. (57) Ploss, E. E. Ein Buch von Alten Farben: Techno-Logie Der Textilfarben Im Mittelalter Mit Einem Ausblich Auf Die Festen Farben; Heidelberg and Berlin, 1962.
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Appendix I Historical recipes
Table of Contents
Lac lake pigments ...... 40 Jehan le Begue, Merrifield volume I ...... 40 Bolognese manuscript, Merrifield volume II ...... 41 Natural colorants for dyeing and lake pigments ...... 42 Manuscript of ibn Bādīs ...... 43 Mappae clavicula ...... 43 Dyeing with lac ...... 44 Ziegler, Kunst und bild buch...... 44 Dye Technique ...... 44 Natural colorants for dyeing and lake pigments ...... 44 Plichto, of Gioanventura Rosetti ...... 44 Cardon – Natural dyes Old india ...... 45 Hellot, The art of dyeing wool, silk and cotton ...... 45 Extracting lac from dyed textiles ...... 48 Jehan le Begue, Merrifield volume I ...... 48 Nuremburg Kunstbuch ...... 49 Bolognese manuscript...... 49 Miscellaneous other useful recipes and references ...... 51 Cennini ...... 51
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Lac lake pigments
Jehan le Begue, Merrifield volume I in the Experimenta de coloribus, Experiments upon colours.
The original manuscript is dated to 1431, written in French. The translation used here is by Mrs 51 Merrifield is from 1849. §12. Also to make lake - Take 1 ox. Of lac, which is a certain gum called lac, or take some of the grana with which scarlet cloths are dyed, and steep it in ley, or in urine, so as to cover the lac, or the grana, and let it boil for half an hour on a moderate fire without smoke, namely, with smith’s charcoal, stirring it continually with a stick whilst it boils. Afterwards take ½ an oz. of roche alum and ½ an oz of sal gem, and grind them well with ley, and put them into the vase before it ceases to boil. Then remove the vase from the fiber, and let it cool. Afterwards take a glazed jar, and a little urine, or strong ley, and empty the before-mentioned jar into it, and stir or shake it every evening and every morning, and after 15 days strain it by means of a linen bag placed upon a new tile, which will immediately dry the lake, which will remain in the bag, and which you may keep for use, and when you wish to use it, grind it well upon a slab, and work with it. And if you like strain the water again, as before directed; and, if you wish to make more lake, boil the said water, and take more of the before-mentioned ingredients, and do as before, and it will be finer than the first mentioned above.
Idem ad faciendum lacham. – Tolle unciam unam lache, que est quedam gumma dicta lacha, vel accipe de grana de qua tinguntur scarlate, et pone in lissivio vel urina viri, tanta que coperiat lacham seu granam, et fac bullire per mediamhoram ad ingem temperatum, absque fumo, videlicet cumcarbonibus fabrorum, deducendo cum baculo sempre dum built. Postea tolle onciam ½ aluminis roche, et onciam ½ salis geme, et mole bene cum lexivio, et postea pone in vase suprascripto antequam cesset bulire. Postea leva vas ab igne, et unum paucum urini hominis, vel de lessivio fortissimo, et mitte simul de super vase, et deduc vel agita omni sero et omni mane, et post xvcim dies cola cum saculo telle lini, posito super tegula nova, que subito siccabit lacham, que remansit in saculo, quam serva ad usum; et cum voles uti, mole bene super lapide, et operare. Et, si vis, recola dictam aquam, prout dictum est; et si plus volueris facere, fac bulire dictam aquam, et accipe de nove de rebus supradictis, et fa cut prius, e terit ista finior quam suprascripta.
De diversis coloribus, A treatise upon various colours §309 To make a very good lake. – Take an ounce of lake3 and rasp finely a little Brazil wood, put it into a clean vessel, then add to the Brazil wood some clean beaten white of egg, and a little alum water. Grind the late with that water and dry it in the sun, and when you wish to use it, distemper it with this water, especially on parchment; and the more you grind it up with this Brazilwood water, the better it will be.
§36. To make lake. – Take urine, and keep it for a long while, and afterwards make it boil until half of it is evaporated upon a slow and clear fire, skimming it continually, until it is perfectly purified. Then strain it through a linen cloth, and put 4 lbs. of it into a glazed jar of the said urin, and 1 lb. of raw lac well ground, and add to it a sufficient quantity of alumine zuccarino, and put it by and keep it for use.
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Ut facias lacham. – accipe uranam hominis bibentis bonum vinum, et diu serva, et postea bullire facias usque ad consumpcionem medietatis, semper despumendo, super lentum et clarum ignem, donec sit optime purgata; postea cola per telam, et pone in vase vitriato libras iiii or dicte urine, et libram unam lache crude, bene trite, et pone de alumina Zucarino quantum sufficient, et repone Servando ad opus.
§37. For the same purpose. – Take gum lac, ground very fine, as much as you like, and put into clear urine for three days, afterwards make it boil on the fire, and skim it. Add a little Roman vitriol to it, and strain it through a linen cloth of loose texture; then add some urine, and make it boil, always stirring it with the ladle, until one fourth part or more is evaporated; then put it in the sun and let it dry, and keep it for use. Ad idem. – Aciipe gumam lache quantum vis tritam subtiliter, et pone in urina nitada per tres dies; postea fac bulire ad ignem, et spuma, postea pone in ipsa parum vitrioli romani, postea cola per pannum lineum rarum. Postea adde de urina, et fac bulire agitando semper cum spatula, donec consumatur circa quarta pars vel plus. Postea pone ad solem, et dimittas siccari, et serva ad usum.
Bolognese manuscript, Merrifield volume II The Bolognese manuscript is dated to the 15th century Bologna in Italy, the translation by Mrs 51 Merrifield is from 1849. Chapter 5, to make lake and pavonazo colours and verzino, De laccis et pavonatijs fiendis in diversis modis et verzinis. Here begins the heading of the fifth chapter, on the making of lakes, purples, and verzino in various manners, and firstly §129. To make good lake. - Take of urine as much as you like, and put it into a vase for the space of a week; then pour it into a pipkin and make it boil until no more scum arises. Then make it into a ley with strong ashes. Next take raw gum lac and pound it as small as panic, put it into a new glazed pipkin, and add to it some of the ley of urine, which must be quite clear, and mix it well with a stick; let the urine or ley be warm when it is poured upon the gum, and when it is well mixed, pour of gently the ley so coloured, and put it into a glazed jar. Then take roche alum in fine powder and mix it with the water; then put some of this alum water into the shell containing the ley coloured with the lac, and when you see that it begins to froth, do not put any more. Then put that which has coagulated into a piece of linen like a strainer, hang it up high, and let the water run off; then take the drainings and put them back into the pipkin where the gum was still left, and mix it up well. Then pour it out, and repeat this another time, thus making 3 sorts of lake; the first best, the second not so good; and the third worst. And know that the ley must be very strong, made with urine, and baked ashes, and it must be poured very hot upon the powdered gum, putting the gum on a strainer of filter of linen; then pour the hot ley several times upon it; afterwards add the alum, and dry it; and also dry by itself what remains in the strainer, and it is done. §130 To make lake as before in another manner. – Take of gum lac 5 lbs., reduce it to powder and sift it through a close sieve; then take filtered urine, which has stood for 20 days, and place a small kettle on the fire, into which put the urine, and when you see the scum which floats upon the urine, remove it with a perforated ladle, and when the urine is well skimmed and warm, add 3 oz. of roche alum in powder, and make it boil again, and then again while it is still boiling take of the scum with the ladle, and when it is well skimmed and clear,
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take the gum lac, sifted, and put it into the urine and alum, continually mixing it over a slow fire for the space of 3 misereres. Then take it off the fire and put it into a clean wooden powder, either rasped or pounded in a bronze mortar, and put it over the fire in a small glazed jar with a little water, and make the said verzino boil; afterwards strain it into a vase through a thin and close woollen cloth, and let it cool for one natural day; then take the urine with the alum which is in the before mentioned wooden bowl, and put into it this water which has been boiled with the verzino and then strain and mix it very well together. Afterwards take 2lbs. of roche alum, and put it into two metadelle of clear water, boil it, and afterwards put the alum water into the urine, and mix it well and let it settle for a day; strain it through a strainer and let it settle for another day. Then let it dry, and when nearly dry, cut it into pieces as you please, and let it dry hard. And observe, that you may make lake in this way from various stones and various kinds, namely, from that from which the crimson colour is made, from dragon’s blood, from grana, from vermiculis, from minio, from verzino, and from the flowers of the herbs.
Natural colorants for dyeing and lake pigments Natural colorants uses the Bolognese manuscript (around 15th century, Bologna Italy) as translated by Mrs Merrifield in 1849. 22,51 The interpretation is written together with the transcription. Recipe from Affare laca bona (Merrifield 1849, vol. 2: segreti per colori, the Bolognese manuscript, 446-7, §129 Make good lake. - take of urine as much as you like and put it into a vase for the space of a week; then pour it into a pipkin and make it boil until no more scum arises. Then make it into a ley with strong ashes. Stick lac – raw gum lac, ground very finely, put in a glazed pot and very hot clear ley is poured on. Mixed very well and poured into another glazed jar. Take roch alum in fine powder, mix it with water, put some of this in the shell containing the coloured ley, until it begins to froth. Put that which has coagulated into a piece of linen like a strainer, hang it up high and let the water run off, take the drainings and put them back in the pipkin with the left over gum and mix well. By pouring off the filtered liquid after the first pigment batch is made and putting it back with the crushed sticklac, three grades of pigment can be made if desired. Alum was added and the pigments filtered off and dried
Traditional late fourteenth- to fifteenth-century Italian recipe. Stale urine – contains ammonia, as alkali, sometimes with wood ashes. Also mentioned is : the Strasbourg manuscript, a 15th century German manuscript were ground sticklac is boiled in the alkali, some of the shellac material will be present in the final pigment. And South German manuscripts describing lac lake Amberg, staatl. Provinzialbibliotek Ms. 77 – the Amberger Malerbüchlein c. 1492 f. 223, Oltrogge: n.d.
The standardised recipe for the fabrication of lac lake pigment as described in Natural Colorants22:
Lac; a typical 15th century recipe 8 g sticklac and grind with mortar and pestle, very coarsely. Put in a 600 ml beaker. In another beaker heat 200 ml of 0.1 M potassium carbonate solution (13.82 g in 1 l demi water) to a simmering point, then pour over the sticklac and stir well. Filter of the purple red solution. Rinse the sticklac residue with a little distilled water and add to the purple solution. Using heat, dissolve 10 g potash alum in 80 ml demi water, making sure the water stays hot. Warm the purple alkaline solution to 50°C and add the alum solution very gradually while stirring until there is no more effervescence, the ph is around 7 and precipitation of the red lake pigment appears to be complete. Leave to settle overnight. The next day filter off/centrifuge the pigment, wash and allow to dry
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Manuscript of ibn Bādīs The earliest copy is thought to originate from around 1025, the manuscript is written in Arabic by al- Muizz ibn Bādīs (1007-1061) whom ilived in Qairawān. The full title is: ‘Book of the staff of the scribes and implements of the discerning with a description of the line, the pens, soot inks, liq, gall inks, dyeing , and details of bookbinding’. The translation provided by Levey has been made using several existing versions of the manuscripts from various dates. 52 Chapter 6 as described by Levey 1962
Another color is red ruby form the lukk. How it is made. Description of how to dissolve the lukk. Ten ounces of lukk are broken up after it has been freed of twigs. Then two dirhams of ushnana and two dirhams of bauraq are pounded very finely. Enough water is poured on to cover them. It is brought to the fire with the lukk until all of the redness of the lukk is brought out (37) it is removed from the fire. It is filtered, returned to the fire, and boiled until half of the lukk solution remains. It is then removed. Write with it. If it is desired that it remains dissolved, a piece of hard white sugar is added to it. If it is desired dry, it is placed in the shade protected from dust. When it is dry, it is removed and used for that which is desired. The lukk is broken into pieces and powdered like the curbled chick pea. It is washed with water and put in a thick filter, hot water is poured on it so that its color, red, will flow from the filter. The filtrate is boiled until it is decreased by two-third. Then dissolved gum is melted in it. Write with it. It comes out well.
Ushnan source of sodium carbonate made of plant ashes, and bauraq source of sodium carbonate/borax. More or less water creates different ph, thus different colour. Mappae clavicula This manuscript is dated to around the 12th century written in Latin, although earlier versions exist which are thought to be originating from 9th century. The text is also called ‘compositiones variae’ or the Luna manuscript, depending on which source is being referenced. It is thought to originate from an Hellenistic source from Tuscany. The translation used here is from Smith and Hawthorne written in 1974. 53 Recipe 253 Lac, how it is worked for painting on wood and on a wall First grind lac and from it pick out the knobbly bits and impurities; then put it in a mill and grind it fine; then take the urine of a man or woman and first put it in a cauldron and let it boil until it is all reduced to a third. Continue always to take off the froth. Afterwards put in the lac and let it boil; then take very clean alum, and grind it and mix it in the above-mentioned lac. Then take a small cloth and keep on dipping it until a good color appears [on it]. Then put the liquid into little pots and work [with it]. Throw out the stone which forms in the liquid, because it is of no value.1 Into 5 pounds of lac put 5 ox of alum and 10 pints of urine. 1. Probably a crystalline lump of superfluous alum or uric acid compounds
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Dyeing with lac
Ziegler, Kunst und bild buch This dye recipe originates from the book written by Marx Ziegler in 1677 in German. The translation used here was made in 1990 by P. Hilts. 54 Beautiful Red on Wool Take tartar and alum and boil the yarn in it for one hour. Let drain. Take Pernambuco or "Maria Holz" (brazilwood) and two Kr. red gum-lac. Let cook together, and when it is boiled, take off the foam and put in the yarn. Let it lay in the bath for half an hour. Afterwards, take it out and wash it. Dye Technique This recipe originates from the website clothroads as accessed on 22-10-2017. 55 It represents a modern method for dyeing with lac as a natural colorant and describes what should be done if the raw material is encountered.
Let’s go to the dyepot. A variety of extracts and ground raw materials are available for dyeing. Simply dissolve the lac extract in water, simmer for 45 minutes, and leave in the dye bath overnight for the richest colors. Use an alum mordant on silk and wool protein fibers for excellent light and washfastness. Be aware that lac is not as lightfast on cellulose. Lac is a water sensitive dye like cochineal, so take care to test your water and decide if you need distilled water. Colors are similar to cochineal, sometimes softer and more muted, although I have dyed with cochineal and lac with similar results.
If you happen to have some sticklac, pound it into a powder and soak for three days, then strain and boil, adding mordants. In Thailand, mead and tamarind leaves (high in aluminum) are used for mordanting fibers. Natural colorants for dyeing and lake pigments The recipes used to mordant with alum as described in the book Natural colorants. 22 How to mordant with alum Make a solution of 2 g potash alum in 500 ml water; heat to 40C until the salt has dissolved. Next add 10 g wool and heat the mordant bath to 90C for one hour. Leave the wool overnight in the mordant bath at room temperature (if insufficient time is available, this step can be omitted). Next, take the wool out of the mordant bath and rinse with several changes of demineralised water. Store the wool wet (in plastic wrap or a plastic bag) prior to use. Note: if only normal tap water is available 0.7 g cream of tartar should be added together with the alum
Material needed : 10 g wool, 2 gr alum (potassium aluminium sulphate, KAl(SO4)2.12H2O), 500 ml demineralised water plus rinsing water, optional 0.7 g cream of tartar (potassium hydrogen tartrate, KC4H5O6, if normal tap water is used)
Plichto, of Gioanventura Rosetti Gianventura Rosetti published the ‘Plichto’ in 1548 in Italy. It is a book containing ‘instructions in the art of the dyers which teaches the dyeing of woollen cloths, linens, cottons and silk by by the great arts as well as the common translation’. The translation from Italian used is made by Edelstein and Borghetty 1969, p142. 39
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§118 To dye silk by means of lac - First you will boil the silk in this manner. Measure one pound of black soap for each pound of silk and put it into a small sack, that is the silk boils in clear water with said soap for a space of one hour. Then wash it in boiling water and then in cold water. Having done this, if it is not white in your manner, you will take again half a pound of soap, and cook it as you did above but do not let it boil but for a half hour and dry it over the sticks. Then take one pound of roche alum, and dissolve it in water and throw away the residue. Then have on the fire some water that is boiling, and before it boils throw inside the silk two or three times and then set it so that it stays until it boils. Then remove it out and set it in the bath of lukewarm roche alum. See that it stays inside for two days, then you take two pounds of gum of lac and pestle it. Take away the rods and then put the silk in a small sack and put it well into the water that is well warm until the said water be well loaded with color. Then put that water into the clean cauldron, and you will take the said water clean and hot. Do as above so it changes color, and when you have enough bath put it to boil, and as it commences to boil, you will throw inside four ounces of white clear tartar and pulverized finely, and stirring well with a pole. Then put inside you silk and have the rods in four parts and leave it boil for one hour never passing it by hand. Then take it out and return it to the alumed water and then take still half a pound of grain and you will do as you did above, but not letting it boil more than half an hour. Then when you will have seethed it take it out from the dyebath wringing the bundles into the alum liquor and leave it to stay for a miserere. Note that it would best be a little new alum solution because it makes the silk lustrous. Also if it were too loaded and uneven, the alumn would open the color. When each thing is done as above said, wash it in the river or the canal, and wring it and drip it and make it dry and spread it so that it remains lustrous. This silk stands in comparison to the grain. And note, make good provision of water always, as you wish to have honour for your workmanship. Cardon – Natural dyes Old india In her book Mrs Cardon describes some practices of dyeing with sticklac she encountered in India where historical recipes are still being used.38
India 3.3kg lac 1kg silk mordanted with alum (and turmeric). Lac broken in small pieces, soaked overnight in 10 l cold water. Lac mass rubbed in some of soaking water on rough surface. Filtered through a cloth. Repeated 3 times with portions of the soaking water. Dyeing in three different baths, each 1/3 of water. And a little tamarind. Between each dyeing silk treated with alum. Hellot, The art of dyeing wool, silk and cotton Translated from the French of M. Hellot, M. Macquer and M. le Pileur D’Apligny, London, Printed for R. Baldwin, Rather-Noster-Row in 178956
Part I, The art of dyeing wool and woollen cloth, stuffs, yarn Worfted etc.
Chapter XV Of Gum Lac Scarlet p 152 – 156 The red particles of Gum Lac is alfo ufed for dyeing Scarlet, and though the colour may not be quite as bright as that obtained from fine cochineal only, it has the advantage of being more permanent.
The Gum Lac moft efteemed for dyeing, is in the form of branches, becaufe moft furnisfhed with animal particles. That which is reddeft in the infide, and at the outfide rather a blackifh brown is the beft. It appeared from a particular examination of Mr.Geoffrie’s, made fome years ago, to be a kind of comb, refembling in fome degree that ufually produced by bees and other infects. It is fometimes ufed for dyeing ftuffs, pulverifed and tied up in a linen bag; but this is a bad method, as fome part of the gum-refin, being melted by the boiling water, efcapes through the linen, and fo slofely adheres to the cloth when cold that you are obliged to fcrape it off with a knife. Ohers reduce it to powder,
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boil it in water, and when it has communicated all its colour, let it ftand to cool: the refinous particles fall to the bottom. The coloured water is then evaporated in the air, where it frequently becomes putrid. When it has acquired the confiftence of fyrup it is preferved in veffels. Under this form it is difficult to determine the precife quantity, and therefore I endevoured to find a method of feparating the colour from the gum-refin, without the neceffity of evaporating fo large a quantity of water.
I shall not mention the variety of experiments which I made with weak lime water, with a decoction of the heart of Agaric, and with a decoction of the root of birth-wort, recommended in ancient difpenfatory; becaufe, though the water left a part of the colour which is had imbibed on the philtering paper, it was neverthelefs too much coloured, and therefore it was neceffary to evaporate in order to procure all the colour. To avoid this evaporation I had recourfe to mucilaginous roots, which of themfelvees yield no colour, but whofe mucilage retains the colouring particles in fuch a manner as to remain with it on the phltre.
I have hitherto fucceeded beft with the Comfrey-root. I ufe it dried and made into a frofs powder, half a drachm to a quart of water, letting it boil for a quarter of an hour; I then ftrain it through a linen cloth, and pour ti quite hot on the Gum Lac, pulverifed and fifted through a heir feive. It immediately acquires a fine crimfon colour. I put the veffel to digeft in a moderate heat for twelve hours, obferving to ftir the gum which remains at the bottom feven of eight times. I afterward decant the water impregnated with this colour into a veffel large enough to contain four times the quantity, which I fill with cold water. I then add a very fmall quantity of a ftrong folution of Roman alum. The coloured mucilage precipitates; but, if the water ftill remains coloured, I add fome drops of the folution of alum to complete the precipitation, proceeding in this manner till the water becomes colourlefs. When the crimfon mucilage is entirely funk to the bottom, I draw off the clear water with a fyphon; the remainder I philtre, and when perfectly drained caufe it to be dried in the fun.
If the firft mucilaginous water does not fufficiently extract the colour from the Gum Lac, fo as to leave the gum a pale ftraw colour, I add fome more, boiling hot, repeating everything that I had dond in the firft extraction. In this manner I feparate all the colour that is capable of furnifhing; but as I had it dried and then pulverifed, I know the whole that may be obtained from this gum, and am alfo better enabled to judge of my quantityies in dyeing than thofe who are fatisfied with the extract procured by evaporation, as that which is moft compact will contain moft colour.
The beft shofen Lac, detached from its branches, yields little more than a fift part of its weight in colour. Hence, confidering the price which it bears at prefent, the advantage of fubftituting it in the pace of cochineal is not fo great.
To dye Scarlet with the Gum-Lac colour, extracted according to my method, and reduced to powder, requires a peculiar precaution in the diluting; for by putting it into the water when ready to boil, as you do the cochineal, you lofe three quarters of an hour before it entirely diffolves. To be more expeditious, I put the quantity of this dry powder, defigned for ufe, in an earthern, or block tin veffel; I then pour on it fome hot water, and when well moiftend, add the requifite quantity of the Scarlet compofition, ftirring the mixture with a glafs peftle. This powder, which was before a dark dirty purple, acquires in the folution a fire colour red extreamly bright. I pour the folution into the liquor, to which I had previoufly diffolved cryftals of tartar, and as foon as the liquor begins to boil I dip the cloth, turning and returning it according to the ufual method. The remainder of the operation is performed win the fame manner as with cochineal. I fancied only that the extract of the
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Gum-Lac, prepared according ot my method, furnifhed about a night part more of colour than the cochineal; at leaft more than the cochineal which I ufed in the comparifon.
If you fubftituete af fixture alkaline falt, or lime water, for cryftal of tartar, the bright red of the Gum- Lac will be changed to the colour of the lees of wine. Hence this colour does not fo eafily crimfon as that of the cochineal.
If infread of thefe alteratns you fubftitute the falammoniac only, you will have cinnamon colours, or light marone, according as you add more or lefs of this falt.
I have befidees made twenty other experiments with this drug, which I fhall not mention, as they produced nothing but fuch common colours as may be more eafily obtained from cheaper ingredients; as I meant only it improve the red colour of the Lac, I have been more explicit in the method of extracting its colouring particles, becuafe the greater the variety of ingredients for dyeing Scarlet, the lefs will be its price. In fhort, all thefe experiments refpecting the cochineal, Lac and other drugs, apparently of fuch little ufe to the Dyers, are of fome confequence to the philofoper in his enquiry into the caufes of the change of colours. From what I have already faid, it is evident that this fubject is enexhauftible. [the colouring particles of the Gum-Lac may be extracted by water only, without any other addition. The water fhould be rather more than warm, and the pulverifed Lac put into a woollen bag, and then trod in the copper. The intelliegent dyer will know how to improve upon this.] Chap XVI Of Crimfon – cochineal Wool when boiled in alum and tartar, the common preparation for every colour. The following is the method generally pracfifed with worfteds; nor is there any great different with regard to cloth, as will be shewn in the fequel. You put int o cauldron tow ounces and a half of alum, and an ounce and a half of white taratr, for every pound of wool. As foon as it begins to boil you put in the wool, ftirring it well, and fuffering it to boil for two hours; it is, then taken out, lightly fqueezed, and put into a bag, in which it should remain, as for scarlet in grian, and for every other colour.
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Extracting lac from dyed textiles
Jehan le Begue, Merrifield volume I in the Experimenta de coloribus, Experiments upon colours.
The original manuscript is dated to 1431, written in French. The translation by Mrs Merrifield is from 51 1849. §11-13 p. 50-53 §36-37 p. 63 §11. To make fine lake – Take the ashes of oak,1 and make a ley, and boil it in clippings of a fine scarlet of rubea de grana2 until the colour is extracted from the clippings, and then strain the ley with the colour through a linen cloth. Afterwards take some more ley, similar to what you first took, and heat it, and put into it some finely powdered roche alum, and let it stand until the alum is dissolved. Then strain it throught the strainer with the other liquor or ley in which the clippings were put, and immediately the ley will be coagulated, and make a lump or mass, which you must stir well. Remove it afterwards from the vase, and lay it on a new hollow brick, which will absorb the ley, and the lake will be left dry. You must afterwards take it of the brick and keep it for use.
1. The Turkey oak, the Cerro of the Italians
2. strictly speaking, “Rubea” means madder, and “Grana” kermes; but as it appears that at this period the kermes was generally used in dyeing scarlet, and the recipes for making this “Lacca di Cimatura” generally direct the clippings of cloth dyed with kermes to be used, it is probable that the kermes was meant in the present case, not madder.
Ad faciendum lacham finam. – Tolle cineres ligni cerri, vel roboris, et fac lecivium, et in ipso fac bulire cimaturam scarlate fine rubee de grana, tantum quod ex dicta cimatura extractus sit color; postea ipsum lessivium, cum dicta cimatura, colla per pannum lineum; postea accipe de alio lexivio simili suprascripti quod prius accepisti, et calefac, et pone in ipso de alumina roche trito subtiliter, et permitte donec alumen sit fusum, postea cumdicto colatorio cola ipsum in dicta alia collatura vel lexivio, in quo stetit cymatura, et subito dictum lessivium stringetur, et faciet unam bussaturam seu massam, quam mistica bene, et postea trahe ipsam de vase, et pone in madono concavo novo, qui bibet lessivium, et remanebit sicca dicta lacha, quam postea trahe de madone et serva usui. §13. To make very fine lake. – Take clippings of very fine scarlet of rubea de grana, and put them into a vase, with sufficient urine to cover the clippings to the depth of one or two fingers’ breadths, and let it stand for some days, until the clippings are decomposed, which you may know by touching them with your hand or your fingers. Afterwards take them out of the vase, without squeezing them, and put them on a clean stone, and allow the liquor to flow out by itself. Then grind it well upon a stone, and strain it through a thin piece of linen, and you will have a fine lake, to use upon paper, parchment, and upon primed wooden panels, but not on walls.
Ad faciendum lacham finissimam. – Accipe cimaturam scarlate fine rubee de grana, et pone in vase cum tanta urnia hominis, que cooperiat cimaturam quantum est grossitudo digiti unius vel duorum, et stet per plures dies, donec dicta cimatura sit bene putrefacta, cujus putrefactionem cognosces tangendo cum manu vel digitis. Postea trahe ipsam de vase absque ipsam exprimere, et pone super mondo lapide et dimitte ipsam per peciam subtilem lini, et habebis lacham finam pro operando in cartis et in tabulis gissatis, set non in muro.
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Nuremburg Kunstbuch Nürnberger Kunstbuch manuscript (1470-1500), Nünberg, Stadtbibliothek, North Bavarian/East Frankish. The manuscript is a German text on pigment manufacturing and manuscript illumination attributed to a nun called Klara Keiperin who lived in Nuremburg in the second half of the Fifteenth century. Transcribed by Ploss in 1962 and translated to English by Jo Kirby.22,57
“If you want to make good Paris red, for a pound of good red clippings take 3 pounds of ashes; pound them small, put them in an earthenware pot and add water, so that the wool will be well moistened there in; let it boil well and then take a feather, put it in and if the feather can be stripped from the quill, the ley(alkali) is strong enough. Remove it [from the fire], let it settle and pass it through a cloth; let it cool and when it is cold, place it on the fire, let it boil and stir the pound of wool into it. Let it boil until you see nothing but a red water; take a little on your hand and spread it out with your finger and if you can see no more hair it has had enough. Take it off and pass it through a thick cloth so that the colour remains on the cloth and throw fresh water onto it for two r three hours so that the ley comes out, then take the colour and grind it well on a stone and grind into it a quarter of ground alum; ut it in a fine vessel and throw in enough fresh water to wet the colour, let it all boil and then pass it through a cloth again.
Bolognese manuscript The Bolognese manuscript is dated to the 15th century Bologna in Italy, the translation by Mrs 51 Merrifield is from 1849, these recipes are published in the volume II. Chapter 5, to make lake and pavonazo colours and verzino, De laccis et pavonatijs fiendis in diversis modis et verzinis Here begins the heading of the fifth chapter, on the making of lakes, purples, and verzino in various manners, and firstly
§110 To make a good and fine lake. – Take 1 lb. of clippings of Rosato,1 and put them into very strong ley made of ashes, such as the dyers use, in a new glazed jar, and set it on the fire to boil, and boil it slowly for the space of two paternosters, then pass the ley and the shavings through a linen strainer, and press it strongly with the hand so that all the ley may pass out; then put back the ley to boil again without the clippings, when it is boiled, throw it on the shavings which hare in the strainer, and press the strainer hard with the hand so that all the ley may run out, and put it by. Throw away the shavings and wash the strainer well, so that there may not remain in it any hairs of the shavings. Next take 5 oz. of roche alum in fine powder, and put it a little at a time into the ley, until the ley begins to settle, which you may know by its turning almost entirely in to a thick scum, from top to bottom, and you must keep on mixing the ley with a clean spoon until it becomes cool and settles; then put the ley into the clean strainer and strain it all off, and the lake will remain on the strainer. Let it remain on the strainer until quite dry, and then put it into a small basin of glazed earth full of clear and cold water, and stir it and rub it up well with the hand until it diffuses itself; all the scum which rises to the top at first must be thrown away with a feather; then wash the strainer well and pour into it the water in which you have put the lake, and the clear water will pass out along with the alum, and this is called purifying it from the alum. And when the lake is nearly dry, remove it from the strainer, and spread it out with a broad knife on a new tile, let it dry in the shade, and before it has done drying, cut it into pieces according to your fancy, and let it dry, and it is done. And know that the more it is purified
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from the alum, the more beautiful and lively, and the better it is. And observe this secret, that if you wish the lake to have a brighter colour and one which will never change, when the shavings are boiling, add a lump of assafetida2 as large as a chesnut.
1. Rosato is a kind of woollen stuff dyed with “grana,” that is kermes. 2. The virtue of this gum resin probably lay in the bitter or extractive principle, for it is know that lakes are more durable if the water used in making them be previously boiled with some astringent bark, such as the bark of the beech, or the small branches of the poplar. §111 To make lake in another manner. – Take baked ashes, such as the dyers use, and make a caustic ley, and keep it clean and clear; then put the ley to boil in a glazed jar, and when it boils, put a lump of quicklime, not slaked, into it, and strain it through a close cloth. Then take 2 “petitti” of this ley clean and fine, and put it into a new glazed pipkin and add to it half a pound of shavings of cloth, mixing it well; then put the ley over a clear fire, and make it boil until reduced to one-third. When it is so reduced, add to it 2 oz. of roche alum, and make it boil until it is reduced one-third; then strain it through a straining cloth into a glazed vase, and put the lake on a new brick that has a hollow in the middle, and little at a time if the brick will not hold it all at once, and let it remain for the space of 5 hours; then take it out and do this as long as any lake remains. Then put it into a basin to finish drying in the heat of the sun, and when it is nearly dry, spread it on a very smooth table, and when quite dry, cut it into pieces according to your pleasure.
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Miscellaneous other useful recipes and references
Cennini The craftsman’s handbook “Il Libro dell’Arte” Cennino d’Andrea Cennini dating from the 15th century in Florance, Italy. Translated by Daniel V. Thomson, Jr. p2640 On the character of a red called Lac.1 Chapter XLIIII A color known as lac is red, and it is an artificial color. And I have various receipts for it; but I advise you, for the sake of your works, to get the color ready-made for your money. But take care to recognize the good kind, because there are several types of it. Some lake2 is made from the clippings of cloth3, and it is very attractive to the eye. Beware of this type, for it always retains some fatness in it, because of the alum,4 and does not last at all, either with temperas or without temperas, and quickly loses its color. Take good care to avoid this; but get the lac which is made from gum;5 and it is dry, lean, granular, and looks almost black, and contains a sanguine color. This kind cannot be other than good an perfect. Take this, and work it up on your slab; grind it with clear water. And it is good on panel; and it is also used on the wall with a tempera; but the air is its undoing. There are those who grind it with urine; but it becomes unpleasant, for it promptly goes bad.
1. Lacca, I translate this “lac”, rather than “lake” because of the indefinite character of the latter. Cennino meant specifically “lac lake,” that is, a lake which is made from the gum lac, “the dark-red resinous incrustation produced on certain trees” (resiniferous species of the genera Schleichera, Butea, Fiscus, etc.) by an insect, Coccus or Carteria lacca. (See NED, s.v. “lac”1 I, 2; also Merck’s Index 1930 s.v. “shellac”) “lake” originally signified the colour made from “lac”1 I , but gradually took on a wider meaning, and the original connection with lac proper is now almost wholly forgotten. 2. Here lacca is used in the general sense of a “lake” color, an organic coloring matter precipitated out on a metallic base, in this case, alumina. No general classification of medieval receipts for “lakes” can be attempted here, but two rules may be cited: the first found in Merrifield, op. cit., I, 63, in the Experimenta de coloribus, §37, may serve to represent the manufacture of what Cennino calls , “the good kind”; while the second, ibid., p 53, §13, “Ad faciendum lacham finissimam,” may stand for the type which he condemns. 3. Cimatura di drappo, o ver di panno. Drappo seems to imply a silk material, as zendaro does; panno may refer to wool or linen. 4. The “Bolognese manuscript,” §110, in Merrifield, op. cit., II, 433-435, mentions specifically that “guando [sic] se fa quella purgationi de lo allumi, tanto e qiu bella, piu viva, et melglio.” 5. See n. 1,
Note on note 1. The question if Lacca refers to any red lake or a lac lake is ambiguous.
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Appendix II Experimental information
Instrumental The HPLC-MS measurements were performed using a 1260 Infinity HPLC system (Agilent Technologies, Waldbronn, Germany) coupled to a Quadrupole-Time of Flight tandem mass spectrometer 6530 Infinity Q-ToF detector (Agilent technologies, Waldbronn, Germany) by a Jet Stream ESI interface (Agilent Technologies, Waldbronn, Germany). Processing was done using MassHunter Agilent software.
PCA calculations were done using the XLSTAT 2018.1.49386 program, settings: PCA type: correlation; standardisation: (n); type of biplot: correlation biplot/coefficient = n/p; output: script statistics.
Scanning electron microscopy (SEM) measurements were performed using a S-3700N HITACH SEM with an inca X-act Oxford instruments electron source with variable pressure.
Aging of samples was performed using an Atlas SC340 solar simulator without UV radiation at a total lux dosis of 0.027 mLux/h, for 28 days results in 18.144 mega Lux at T = 40°C and 50% RH.
Colourimetry was performed using the processed multispectral imaging photographs in visible light. The average colour values of the largest area possible were taken using the LAB values obtained in Photoshop, corrected the a* and b* intersection being at 0. Colourimetry was also performed using a Minolta spectrophotometer cm-26ood, processing using spectra magic NX software CM-S100w 2.51.0003 d.
FTIR measurements were performed using a Nicoleet 6700 FTIR (Thermo Scientific).
Imaging was done using a modified Nikon D7000 camera, DX AF-S Nikon 35 mm 1:1:8 G lens and a XNitecc1 365-635 nm filter for visible light, RG830 filter for IR, KV418 filter for UV. Processing was done by Joanne Dyer at the British Museum. Chemicals All solutions were prepared using deionised water (18 Ω) . Stick lac (Tachcerdia lacca) was obtained from Kremer Pigmente (Aichstetten, Germany). Dimethyl Sulfoxide (DMSO 99.0 %) Potash
(Potassium carbonate), urea, alum (potassium aluminium sulphate KAl(SO4)2.12H2O), obtained from Sigma Aldridge. Analytical conditions Sample preparation Lac lake pigment directly from sticklac 6 g raw sticklac was grinded finely using a coffee grinder and put in a satchel of polyester netting. 150 ml of 0.1 M potash solution (13.82 g/l, pH 11) or 0.1 M urea solution (6.1 g/l, pH 7.05) was heated to a temperature of 50°C and poured on the sticklac, left for 1 hour at room temperature or boiled for 10 min. The satchel containing the sticklac residue was removed, rinsed with water. 10 grams of alum was dissolved in 80 ml water (0.26 M) and heated until dissolved. The colourant solution was heated to 50°C, the alum solution was added slowly under stirring. The solution was left to settle, decanted, and the precipitate washed by adding water. The resulting pigment was filtered over coffee paper and washed several times with water. Left to dry inside the fume cupboard.
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Mordanting silk with alum22,38 15.4 grams of alum was dissolved in 2 l water heated to 40°C, after which 44 g silk(35% w/w) was added and the solution was heated to 70°C for one hour, stirring occasionally. This was left to stand at room temperature overnight. The silk was taken out of the bath and rinsed multiple times with water. Stored moist in air tight containers. Mordanting between dye baths: solution of alum (15% w/w), heated with the silk for one hour at 70°C, rinse and repeat dye process.
Other parameter tried was using 20 day old urine reduced by halve to obtain an alkaline solution. Dyeing silk with sticklac 6 g raw sticklac was grinded finely using a coffee grinder and put in a satchel of polyester netting. The colourant molecules were extracted by soaking the satchel in 500ml water at room temperature for three days or by heating at 100 °C for one hour with occasional stirring. Afterwards the satchel was taken out and rinsed. Add 5.5 grams of alum mordanted silk to the colourant solution and heat to 70°C for 1h, while stirring for homogeneity. Take the silk out of the dyeing bath, rinse with cold water and allow to dry. When dyeing multiple times with mordanting inbetween, divide the original colourant solution into three equal portions.
Other dyeing parameters following the same recipe:
- Three consecutive pieces of silk dyed in the same dye bath (hot extraction) - Pigment extraction in a hot alkaline environment (100 °C, 0.1 M potash solution pH 11), and consequently dyeing in an alkaline environment. Extraction of lac from dyed clippings 2.5 grams of lac dyed silk cut into small clippings and put in a polyester netting satchel which was added to 100 ml of 0.1 M potassium carbonate solution and brought to a boil for 15 min or left standing for 3 days at room temperature. The satchel was taken out and rinsed. 5 g potash alum was dissolved in 25 ml water using heat. The colourant solution was heated/cooled to 50°C and the alum solution was added slowly under stirring. The solution was left to settle, decanted, and the precipitate washed by adding water. The resulting pigment was filtered over coffee paper and washed several times with water. Left to dry inside the fume cupboard sample extraction 0.1 mg of sample was mixed with 200 μl DMSO and the closed vial was heated for 10 minutes at 80 °C. The solution was centrifuged after which the supernatant was transferred into another vial (DMSO fraction). The residue was mixed with 200 μl of methanol/acetone/water/0.5M oxalic acid 30:30:40:1 (v/v/v/v), put in an ultrasonic bath for 5 min and heated at 80 °C for 15 minutes. The
liquid was evaporated under nitrogen and resituated in 200 μl of MeOH/H2O (v/v). The two extracts were combined and punt in an ultrasonic bath for 5 min before being centrifuged for 5 minutes at 4000 rpm.
Liquid chromatography A Zorbax Extend-C18 column (2.1 mm x 50 mm, 1.8 μm particle size) was used at a flow rate of 0.4 ml/min, column temperature 40 °C. The mobile phase consisted of 0.1 % formic acid in water (mobile phase A) and 0.1 % formic acid in ACN (mobile phase B). The injection volume was 10 µl unless stated otherwise. The binary pump was set to gradient elution with a time program of 22 min: 0.0 - 10 min, linear gradient from 95% A, 5% B to 100% B; maintained at 100% B for 2 min; 12.0-13.0 min, linear gradient to 95% A, 5% B which was maintained for 10 min.
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Mass spectrometry
ESI operating conditions were: drying gas (N2, purity >98%), 350 °C, 10 l/min; capillary voltage 4.0 kV; nebuliser gas 40 psig; sheath gas (N2, purity >98%), 375 °C, 11 l/min;
High resolution MS spectra were obtained in negative mode in the range of 100-1700 m/z. The fragmentor was set at 150 V, nozzle voltage 1000 V, skimmer 65 V, octapole RF 750 V.
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Appendix III Multispectral Images
Visible reflectance (VIS)
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Reflectence Infrared false colour image (IRR)
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Ultraviolet reflectance false colour image (UVR)
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Ultraviolet induced luminescence (UVL)
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Vissible induced visible luminescence (VIVL)
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Lac sources in Hellenistic pigments
Multispectral images of unaged textiles H3.2
Tu Tu_C1 Tu_C3 Tu_H1
Tu_H3 Tu_H3.1 Tu_H3.2
Figure 10 The multispectral images of the unaged dyed textiles. Top left visible reflectance, top right reflectance infrared false colour, bottom left ultraviolet reflectance false colour image, bottom right ultraviolet induced luminescence.
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Multispectral images of aged textiles
Ta Ta_C1 Ta_C3 Ta_H1
Ta_H3 Ta_H3.1 Ta_H3.2
Figure 11 The multispectral images of the aged dyed textiles. Top left visible reflectance, top right reflectance infrared false colour, bottom left ultraviolet reflectance false colour image, bottom right ultraviolet induced luminescence.
61 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Appendix IV SEM images
Figure 12 SEM images of silk Tu_C1 at 40x and 300x magnification
Figure 13 SEM images of silk Tu_H1 at 40x and 300x magnification
Figure 14 SEM image of silk after the extraction of pigment TP_C1_C , at 40x and 300x magnification
62 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Figure 15 SEM image of silk after extraction of pigment TP_C1_H, at magnification 40x and 300x
Figure 16 SEM image of silk after extraction of pigment TP_H1_C, at magnification 40x and 300x
Figure 17 SEM image of silk after extraction of pigment TP_H1_H, at magnification 40x and 300x
63 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Figure 18 SEM image of untreated silk at magnification 40x and 300x. Sample very dirty
64 Berbers, Uva 2018 Lac sources in Hellenistic pigments
Appendix V PCA of extended dataset
3 DP_H_N DP_C_A DP_H_U 2 Ta_H3 Tu_H1 Ta_H1 Tu_H3.2 Ta_C3 Ta_H3.1 Ta_H3.2 Tu_H3.3 1 Tu_H3 Tu_H3.1 Ta_C1
Tu_C1 DP_H_A 0 Tu_C3 TP_H3_C TP_H3.1_C TP_H3.1_H -1 TP_H3.2_H PC2 (25.43 %) TP_C3_HTP_H1_C TP_C1_H Tu_H_A TP_C3_C TP_H1_H TP_H3_H TP_C1_C -2 TP_H3.2_C
-3 DP_H_A_T
-4 -4 -2 0 2 4 6 8 PC1 (41.28 %)
1 Al-Jal Al-Lac 0,75
0,5
0,25 Polyesters
0
PC2 (25.43 %) -0,25 Shellac colourants Laccijalaric Lac acid -0,5 Jalaric acid colourantsButolic acid Aleuritic acid -0,75
-1 -1 -0,75 -0,5 -0,25 0 0,25 0,5 0,75 1 PC1 (41.28 %)
65 Berbers, Uva 2018 Lac sources in Hellenistic pigments
3
TP_C3_H 2 TP_C3_C Ta_C3 DP_C_A TP_C1_C Tu_C3 1 TP_C1_H DP_H_A Ta_C1 Tu_H_A Tu_C1 Tu_H1 DP_H_A_T
0 Tu_H3 DP_H_U TP_H1_CTu_H3.1 DP_H_N TP_H1_H Ta_H3.1 Tu_H3.2 Ta_H1 Ta_H3Tu_H3.3 TP_H3.1_H -1
PC3 (13.33 %) Ta_H3.2 TP_H3.1_C TP_H3_C TP_H3_H -2 TP_H3.2_C
-3 TP_H3.2_H
-4 -4 -2 0 2 4 6 8 PC1 (41.28 %)
1 Shellac 0,75 colourants
0,5 Lac colourants
Al-Lac Polyesters 0,25 LaccijalaricJalaric acid acid 0 Aleuritic acid Al-Jal
PC3 (13.33 %) -0,25
-0,5
Butolic acid -0,75
-1 -1 -0,75 -0,5 -0,25 0 0,25 0,5 0,75 1 PC1 (41.28 %)
66 Berbers, Uva 2018