Friday, 19 October 2012

The Lexden Boar — Victim of Acid Attack?

After giving the discrepancy between the two pictures of the Lexden Boar a day's thought I think I have at least a plausible theory as to why they should be so very different.

Firstly I think the two pictures are of the same object but one is reversed. The angles are different and shot with different focal length lenses too but I don't think I've ever seen two Iron Age items (though this is Gallo-Roman in a British Iron Age context) so very similar to each other. This item would have been a one-off lost wax casting and another would have required a new wax model to be made because the process destroys it just as the name of the technique suggests. They are just too similar to be different objects from different places, I think, and I doubt that Miranda green would have made such a mistake even if were possible.

I'm beginning to think that this figurine has been inexpertly 'cleaned' some time soon after excavation. The excavation took place in 1924. Most Iron Age objects found before this date were routinely removed of all trace of patina because the 'standard' at this time was that set by the famous Iron Age finds from the Thames such as the Battersea Shield and Waterloo Helmet, all of which actually came up in river dredging perfectly preserved, un-patinated and naturally a bright bronze colour, which is quite normal for copper alloys from the anaerobic muds of the Thames as any mudlark will attest. It is almost unknown from soils though, where patinas will certainly develop well on copper-based objects and be heavy to the point of almost total conversion of metal to copper compounds in some.

The results of this highly jeopardous curatorial 'fashion' for stripping back Iron Age objects to the bare metal can be seen with many of the most famous treasures of the period in the British Museum collections with objects that were originally patinated to some degree or even to a considerable degree.

The Trelan Bahow Mirror
The Stanwick Horse

The Trelan Bahow Mirror is bright bronze and so is the Stanwick Horse, but they both would have been green — brown on discovery, as you can imagine with ancient finds from average soils and not anaerobic muds. The mirror shows what happens when what must have been a fairly thick patina is removed to expose a bronze surface — lots of detail is lost and vulnerable edges are bitten clean through because often whole areas of metal are converted in the ground into copper chlorides, sulfides, sulfates and carbonates, all of which are easily soluble in acids whereas the metal is far more resistant.

The truly beautiful Stanwick Horse has thankfully survived the acid test with just a little pitting around the forehead which suggests it was lightly patinated when found.

I reckon the early picture of the Lexden boar is of it when fully patinated, and the second of how it is now but after acid removal of patina some time back in the 1920's when thin areas such as the tip of the lower jaw and the lower parts of the legs, all of which may well have been converted completely from metal into other chemical compounds, suffered very badly and simply dissolved away to nothing.

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