Let me just confirm the process.
Pickle contains acid. It will be sulphuric acid (as the bi-sulphate
in safety pickle) , acetic if you use vinegar, citric if it’s lemon
juice - they all work quite well but sulphuric is the fastest and the
best if the most dangerous.
Silver and gold alloys contain copper which forms a salt with the
acid and this is soluble. So after a very short time your pickle
contains a copper salt. If there’s enough of it you’ll see the pickle
has turned blue!
Any two metals in an acid environment will have a galvanic electrical
current run through them. This is what causes metal ships to corrode
so fast and why they have sacrificial metallic plates put on them.
The current flows from the silver/gold to the copper tongs when you
reach in to pick up you piece and no metal is deposited on the copper.
The acid just eats away a bit of the tongs. If you use an iron tool to
retrieve your piece the current flows the other way, the iron goes
into solution and the copper is thrown out of solution onto the
The deposit is always of copper onto the noble metal.
If you need a fine deposit of copper onto gold or silver for
granulation - in order to for a eutectic alloy - this is a useful
process. Otherwise its a bloody bother!!
Tony Konrath Gold and Stone www.goldandstone.com