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Slags and Old Ores at Swandro – evidence of high status metalworking

Its day T minus one and counting – all hands on deck or rather all boots on beach tomorrow morning bright & early!

We’ve got some very special guests coming up this year to lend us their professional expertise, one of them is no less than the eminent archaeometallurgist Dr Gerry McDonell. He’s an old hand in the Northern Isles having been involved in projects in Sanday back in the 1980s - I seem to remember if asked what his speciality was he used to reply ‘Slags & Old Ores’ and then giggle manically. We were all a lot younger then and may have imbibed the odd shandy or two – he’s very respectable these days (others of us less so!).

Anyhow you can tell an awful lot about metallurgy from slag: take this very fine example of spheroidal slag from last year:

Spheroidal slag at the Knowe of Swandro
Spheroidal slag at the Knowe of Swandro

This just looks like a load of yick to me, but it is actually spheroidal slag produced by fire welding and indicates evidence of sophisticated and very skilled iron working. There’s also hammer scale – which is all the bits that flake off a bit of hot iron when you’re whacking it with a hammer, so they’re forging iron at Swandro. There’s also loads of bits of crucible some with residue of metal working and droplets/fragments of copper alloy, which Gerry’s been looking at with a XRF (X-ray fluorescence) machine:

Gerry McDonnell & his XRF machine in the lab at Bradford
Gerry McDonnell & his XRF machine in the lab at Bradford

The crucible fragments and bits of slag are at Swandro are really interesting – they all come from a Pictish building, and the Picts are known for making copper alloys - what we used to just call bronze but the metallurgists get a bit huffy about that: to be technically correct the Picts made tin/copper alloy and tin/lead/copper alloys. The Vikings however reintroduced brass to Britain – that is zinc/copper alloys, as a result of reopening trade routes to the east.

BUT just to confuse you completely – we’ve got brass ( zinc/copper) metalworking in a Pictish building at Swandro where it isn’t supposed to be at all – so there’s something weird going on here.

Gerry is very keen to see this for himself hence the trip back to Orkney – we’ll keep you posted on whether we can find him some nice slags when he’s here!


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