As far back as the seventh century, they had metallurgical tricks to make poor quality gold jewellery look far better:
Scientists, examining Britain’s greatest Anglo-Saxon gold treasure collection, have discovered that it isn’t quite as golden as they thought.
Tests on the famous Staffordshire Anglo-Saxon treasure, a vast gold and silver hoard found by a metal detectorist five years ago, have now revealed that the 7th century Anglo-Saxon goldsmiths used sophisticated techniques to make 12-18 karat gold look like 21-23 karat material.
Scientific research, carried out over the past two years on behalf of Birmingham City and Stoke-on-Trent City councils, which jointly own the hoard, has revealed that the Anglo-Saxon goldsmiths had discovered an ingenious way of, metallurgically, dressing mutton up as a lamb. It appears that they deliberately used a weak acid solution – almost certainly ferric chloride – to remove silver and other non-gold impurities from the top few microns of the surfaces of gold artefacts, thus increasing the surfaces’ percentage gold content and therefore improving its appearance. This piece of Anglo-Saxon high tech deception turned the surfaces of relatively low karat, slightly greenish pale yellow gold/silver alloys into high karat, rich deep yellow, apparently high purity gold.
Archaeologists had never previously realised that Anglo-Saxon goldsmiths had developed such technology.
“We had no idea they were doing it,” said Dr Eleanor Blakelock, a leading British archaeometalurgist who carried out the tests on the Staffordshire hoard gold.
H/T to David Stamper for the link.
