Postby JBA » Thu Feb 23, 2012 8:02 am
I imagine they were testing only for Sterling silver, and when the acid did not reach the desired colour, called it a failed test. Where they by any chance interested in buying the item?!
Legally in the UK, silver has to be 92.5% pure (sterling), or it is actually illegal to sell it under the term "Silver". Anything less has to be called "White Metal". I think the same applies in the US, save for the fact that you also (since 1906) have the legally defined term "Coin Silver", which I believe to be 90% purity.
The sort of acid I use works as follows: One looks for a blood red colour in Sterling silver. Lower grade silver gives a lighter and more orangey red. Base metal stays completely orange.
The deeper the red the higher the silver content.
However, perhaps people who only encounter sterling silver (925) or coin silver (900) regularly do not fully understand the appearance a lower grade silver result.
FYI- By most people's standards .800 is high grade silver. I use the term lower to denote that it is less pure than sterling. Proper "Low Grade" silver by generally accepted terminology is 75% pure or less. Terminology is a bit sketchy and inaccurate though, but hard to avoid!