Årsskrift För Sigtunaforskning Och Historisk Arkeologi 2011 Utgiven Av Sigtuna Museum
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situne dei Årsskrift för Sigtunaforskning och historisk arkeologi 2011 Redaktion: Rune Edberg och Anders Wikström Utgiven av Sigtuna Museum SITUNE DEI Eyvind Skáldaspillir’s silver – refining and standards in pre-monetary economies in the light of finds from Sigtuna and Gotland Anders Söderberg t is said that in the first half of the 10th marks. This they sent to Eyvind; but Eyvind Icentury, when the court poet of King had the shoulder-pin broken into pieces and Hakon the Good, Eyvind Finnsson Skál- with the silver he bought a farmstead for daspillir, had composed a poem to the himself.” (Foote 1961:125f) honour of the Icelanders, it was decided to In other translations keypti sér bú með is reward him by making him a cloak-pin. variously translated as “bought cattle with it” or “obliged to…buy food for his house- ”Eyvindr orti drápu um alla Íslendinga, en þeir hold”. The phrase “…at hverr bóndi gaf ho- launuðu svá, at hverr bóndi gaf honum skattpen- num skattpening. Sá stóð þrjá penninga ing. Sá stóð þrjá penninga silfrs vegna ok hvítr silfrs vegna” has also been translated as í skor. En er silfrit kom fram á alþingi, þá réðu “each bonde [farmer] offered a scatt penny menn þat af at fá smiða til at skíra silfrit. Síðan of pure silver equal to three weighed penni- var görr af feldardálkr, en þar af var greitt es” which is supposed to be a reference to smíðarkaupit. Pá stóð dálkrinn fimm tigu mar- imported debased Anglo-Saxon pennies, of ka. Hann sendu þeir Eyvindi, en Eyvindr lét hög- which three were equal to one penny of fine gva í sundr dálkinn ok keypti sér bú með.” silver (Dasent 1861:405). (Heimskringla: Sagan af Haraldi konungi James Graham-Campbell (2007:216) gráfeld:18. Aðalbjarnarson 1941–1979:221f). and Gareth Williams (2007:182) draw attention to this episode from Heimskringla, “Eyvind composed a poem about the people as it sheds light on several different aspects of Iceland, for which they rewarded him by of the handling of silver. In different situa- each bonde giving him three silver pennies, tions the very same silver is treated as of full weight and white in the fracture. And counted coins when collected as tax; as when the silver was brought together at the jewellery and a status gift; and finally as General Thing, the people resolved to have weighed hack silver in a market situation. it purified, and made into a shoulder-pin, The story illustrates how different systems and after the workmanship of the silver was of exchange were adopted for different pur- paid, the shoulder-pin weighed some fifty poses, and how old and new traditions could 5 SITUNE DEI Fig. 1. Cupellation of silver: 1) recycled silver is molten together with an excess of lead in a hearth lined with a bone ash material. 2) Oxygen is blown over the molten metal. 3) The hearth material absorbs the oxidised lead (litharge) and other impurities. Drawing by the author. – Kupellering av silver: 1) Silver för återbruk smälts samman med ett överskott av bly. 2) Syre blåses över den smäl- ta metallen. 3) De oxiderade föroreningarna absorberas av härdväggen. be interchanged in a way that probably was Refining silver a reality for 10th century Scandinavia. In Silver was refined by cupellation (fig. 1). addition to this, the story reflects a clear This technique first appeared c. 3000 BC in awareness among the Scandinavians of the connection with silver mining. The technol- value and different grades of silver. There ogy became widespread and was used on a are, as both Graham-Campbell and Williams show, aspects of value measured by weight, and of fineness of quality tested by pecking or carving as indicated by the quality criterion “white in the fracture” (hvítr í skor). There is also the small but im- portant verb skíra – to purify, to cleanse, to baptise (Vifgusson 1874:550). This word refers to the process of refining the silver to maximal purity and was performed before transforming it into the gift for Eyvind. Clearly, accumulated metal went through a full refining process before reuse. Even though the story was recorded some 300 years after the event, this alleged informa- Fig. 2. Hearth material (litharge cakes) from sil- tion about Viking customs is of great inter- ver refining hearths is heavy, due to a high lead est, as several finds of early silver re fining content, grainy and sometimes contains tiny waste have recently come to light in Scan- bone fragments, grey with a green zone close dinavia. The refining of noble metals has to the surface and slightly bowl-shaped in sec- tion. 12th century litharge material from Träd- long been associated to minting, but the gårdsmästaren, Sigtuna (find no 5952). Photo Eyvind story may also help us to place these by the author. – Härdmaterial från silverraffiner- finds in the context of the management of ing är påtagligt tungt p.g.a ett högt blyinnehåll, silver in pre-monetary Scandinavian grått och kornigt med ibland synliga smärre bullion economies. benfragment, lätt skålformat i profil och med en grönaktig zon närmast ytan. 6 ANDERS SÖDERBERG Fig. 3. A fragment of Fig. 4. A scorifier a small scorifier from fragment, Sigtu- the workshop area na, late 10th near the Birka town century, Träd- rampart, probably gårdsmästaren, from the 10th century Sigtuna (find no (find no 1071). 10532) Drawing Drawing by the by the author. a u t h o r . – Fragment – Skärvelfrag- av en liten skärvel ment, sent 900- från verkstäderna vid tal. Sigtuna. Birkas stadsvall, troli- gen 900-tal. Fig. 5. A small scorifier with gold droplets, early 11th century, Urmakaren, Sigtuna (find no 5195). Photo by the author. – Liten skärvel med gulddrop- par, tidigt 1000-tal. Kv Urmaka- ren, Sigtuna. large scale, as for example in the antique 1999). In these cases the aim is to drive out silver mines of Larium, Attica, a few the copper and other alloying metals, in thousand years later (cf. Conophagos order to obtain silver of maximal and 1980). The basic principle of cupellation in known silver content. During the first the mining process is melting argentiferous millennium AD the method was further de- lead in a hearth lined with a porous materi- veloped into a technique for testing or al of bone ash and clay (fig. 2). Oxygen is assaying noble metal content in smaller blown over the melted alloy whereupon the samples. This could be considered man’s lead is transformed into molten lead oxide, first invention of a method of analytical litharge, that also absorbs oxidised copper chemistry. The technique came to be linked and other metal oxides. The molten oxide is with the use of precious metals in mining, then skimmed off or absorbed by the porous goldsmithing, as symbols of value and ob- hearth material. The silver, which doesn’t jects for payment and to test the silver con- react with oxygen, stays in a metallic state tent in copper and lead in market situations and is thus refined to a concentration of up before fixing the price (Martinon-Torres, to 99%. Nils Björkenstam (1989:149ff) of- pers. comm.). Fire assay is per formed as a fers a good description, in Swedish, of the process of two steps, wherein the sample is process as used in the 17th century silver melted together with an excess of lead in a mines of Piteå in northern Sweden. small ceramic vessel, a scori fier (figs. 3–5), The same technology was used to refine and the molten alloy is then cupelled in a recycled silver. In this process lead is added vessel, cupel (fig. 6), made from absorbent to the silver in question (cf. Rehren & Kraus bone ash. The sample is weighed before the 7 SITUNE DEI Fig. 6. A small cupel, probably made from bone Fig. 7. A muffle for covering the test hearth, ash. Probably 10th century. Stray find from according to Agricola 1556 (after Hoover & Birka (find no SHM 8985:14). Drawing by the Hoover 1950). – Ett valv att täcka testhärden a u t h o r . – Litet kapell, troligen av benaska. Lös- med vid silvertestning enligt Agricola 1556. fynd från Birka. test, as is the silver remaining afterwards, is nothing until the early 11th century finds and the difference reveals the purity of the from King Olof Skötkonung’s mint on the tested silver. Renaissance test furnaces we- Urmakaren site in Sigtuna and the Hum- re easily put together by using a portable legården site in the same town. The next muffle (fig. 7), creating a space free from find dates from the mid-11th century, and charcoal for maximal oxi dation, and also comes from a silver workshop at Fröjel, for directing the toxic lead fumes away Gotland (Söderberg & Gustafsson 2006; from the assayer. A similar solu tion was Gustafsson & Söderberg 2007). Rich finds probably used in early medi eval Scandina- of cupellation waste have occurred in late via, but so far no traces have been identifi- 12th century contexts associated with mint- ed of these kinds of objects. Scorifiers and ing and exclusive jewellery production on cupels are generally found in medieval and the Trädgårdsmästaren site at Sigtuna Renaissance mints (cf. Wad sten 1979; Mc- (Kresten & Larsson 1996; Söderberg & Lees 1996) and they also seem to have been Gustafsson 2007). Apart from these there is the alchemists’ favourite vessels in their ar- an exclusive group of finds that deserves senal of containers used for different che- mention: ceramic vessels with no obvious mical and metallurgical processes (cf. Mar- admixture of bone ash, from building group tinon-Torres & Rehren 2005).