Tuesday, February 28, 2006

Metalworking at Skamby

As previously mentioned here and here, me & my friend Howard dug a 9th century boat grave at Skamby last summer and found that the place had also been a settlement site in the last century BC. The culture layer contained way too much burnt daub from the walls of a building, a little pottery, and not much else.

Well, there were these bubbly or shiny pieces of very lightweight clay that had clearly seen even worse heat than the daub. When I was washing the daub a few bits of the stuff actually floated in the water like dirty styrofoam. We called it slag during fieldwork, and then I reckoned it was just clay heated to a temperature where the quartz had melted to glass, so now it's vitrified clay in the finds list. 30 grams all in all. Helluva house fire, I thought.

Then I gave a talk in Linköping a few weeks ago, and in the audience was my colleague Dr Erika Räf, who told me a house fire is unlikely to vitrify clay. To get that kind of heat, you need a charcoal furnace and a set of bellows. She suggested I send the stuff to her hubby, Dr Ole Stilborg, who carries on the ceramo-tech torch that Birgitta Hulthén lit in Lund.

So I did. And now Ole tells me that those ugly little bits are pieces of crucibles and casting moulds, all probably used to cast copper alloy! The reason that they're vitrified is that they've been in contact with molten metal. We can't say what kind of objects were cast, but it's still a pretty big deal, because it means we've found one of a very few identified metalworking sites of Pre-Roman Iron Age Scandinavia.

Still, the dating is a little iffy. Most finds of this type of crucible -- the "Helgö type" -- are 500 years later than the radiocarbon dates that we think represent the time of the settlement. It's possible that the metalworking took place at a time that is visible neither in the radiocarbon dates so far nor in the humble artefact finds from the culture layer. But until someone finds more evidence, I'll use Ockham's razor and assume that the metalworking is also last century BC.

Update: I think I kind of understated just how uncommon this find is if the dating holds. Turns out that, all in all, copper alloy casting guru Anders Söderberg and Ole Stilborg know of two other bronze casting sites of the Scandinavian Pre-Roman Iron Age. Both are in eastern Jutland: one at Vitved and one at Egebjerg.

Andersen, S.H. & Madsen, H. 1984. Ett førromerskt bronzestøbefund fra Vitved i Østjylland. Hikuin 10. Viborg.

Kristiansen, Anne Mette & Fristed Jensen, Trine. 2005. Kronehalsring. Skalk 2005. Højbjerg.
[More blog entries about , , , ; , , , .]


Post a Comment

Links to this post:

Create a Link

<< Home

eXTReMe Tracker