Hi All We have found the best way to test silver is with Nitric
acid,file surface to be tested so that it is clean adrop of nitric on
the area ,if sterling or higher it will go grey and then after a time
go black (you have just made silver nitrate) if it goes green it
contains copper .The faster it goes green and the more it goes green
the more copper it contains.
A set of test samples from 50%silver up in steps of 5% are very
useful,and with practice the silver content is easy to find.Test
samples are very easy to make. For the 50% silver sample melt one
gram of silver with one gram of copper ,clean in acid and then pass
through rolling mill.
Allot of the silver that is coming out of India as a high copper
content up to 40%,we have not found it alloyed will Nickel but atimes
with Zinc or Tin. There are some nice things coming out of India but
make sure who you deal with you can not send it back .