A few days’ worth of Digests didn’t arrive last week so I’m not sure
if my post thanking everyone made it into the Digest. I guess that’s
what happens when you live on an island.
I wanted to thank everyone for their input and especially Charles
for his in the archives and Niels on Bornholm, Denmark
for the following post:
Potassium nitrate KNO2 4 parts per weight Potassiumaluminumsulphate KAl(SO4)2, 12 H2O 2 ppw and Sodium chloride (salt) 2 ppw Add water till a thin slurry is reached. Fill into a fireproof container (not metallic) and boil. Suspend the item to be 'surface enriched' from a silver wire into the solution and let boil for 10 - 20 minutes. Clean and scratch brush. Repeat as necessary. A warning: Do not let the piece rest on the bottom, it simply dissolves (I speak from experience :-)
This procedure is very effective because it doesn’t require that the
alloys in 18k be turned into oxides prior to depletion gilding. The
items that I’m working on will lose all of their structural
stability if they are heated to the point of oxidation, therefore
heating them prior to pickling isn’t an option.
If the item is left in the solution for too long, it starts to form
a brownish-reddish skin that is relatively difficult to remove so
timing is important.
It would be interesting to hear from the chemists in Orchidland as
to what is occuring when the above procedure is used.