As I’ve said several times before, I’m from Stoke-on-Trent, and one of the most interesting things to happen to our City (and indeed our county) for quite a long time was the discovery in 2009 of the Staffordshire Hoard. I was one of the many people who queued to see it when it first went on display five years ago, and it was this that inspired both my dissertation and my enduring love of the Anglo-Saxons, which I hope to potentially pursue academically in future years. I came across a story in the news last week regarding this, and thought it worthy of sharing.
It turns out that some of the pieces within the collection are not quite as pure as you would expect, and that Anglo-Saxon goldsmiths occasionally tricked their royal clients using rather clever methods. Two years of research funded largely by English Heritage has shown that the makers of some of the material in the Hoard used a weak solution of ferric chloride (thought to have been made by heating up a mixture of water, salt and iron-rich clay [or maybe dust from crushed up old Roman tiles]) to remove silver and other impurities from the top few microns of gold at the surface in order to enhance the visual purity of the material. The Anglo-Saxons are known to have used this method for creating contrasts between shades of gold, this is the first time such a method has been observed as being used to enhance the purity of the metal. This would have altered greenish pale-yellow, gold/silver alloy of around 12-18 karat into deep gold, 21-23 karat material.
By comparing the Hoard material with that from Sutton Hoo, it is now thought that items made for royalty were being produced of pure gold, whereas that for the lower nobility was made from this chemically-altered alloy. There is also the possibility that this sort of surface purification may also have taken place in order to make the best of the quality of the gold used to make the item- perhaps the objects which have been treated in this way were of a slightly later date than those with the purer body, and were made from substandard gold. It is known that the quality of gold coming into England from the Continent declined over the 6th and 7th centuries, and so we could be seeing evidence of this here.
As with all of the work surrounding the Hoard, it seems that for every discovery made, there are twice as many questions raised!
To keep abreast of the latest news about the Hoard and for some rather interesting scientific articles regarding analysis of various pieces, check out the Staffordshire Hoard website: http://www.staffordshirehoard.org.uk/