I have really enjoyed reading all the postings and have learned a
lot. Now I would like to post a question of my own: Is it possible
to depletion gilding with nitric acid? When I depletion gild with my
Sparex pickle, I can remove the copper but not the silver from my
gold alloys. I have read that it’s possible to depletion gild both
the copper and the silver from the surface of a piece of gold with a
nitric acid solution. However, I cannot find any details about how
to do so, specifically what concentration of nitric acid should be
used. I welcome all of your advice!
Sulphuric acid heated and the work piece dipped in to it will help
you get the result as pure gold will rise on to the surface giving
the piece a rich look.
Use lab grade sulphuric.
A word of caution good ventilation and respirator mask a must.
Maggie- Pure gold can be brought up to the surface of a karat gold
piece but I list this one under the heading “Don’t try this at home
kids”.
The way we did it back in the stone age was. Place cyanide in a
pyrex beaker. A metal beaker will not do. Heat it up like the milk
for a latte by using the nozzle of the steamer. When it’s hot add a
squirt or two of very highly concentrated Hydrogen peroxide. Heat
again with the steamer nozzle until it explodes. Rinse with fresh
water. Your 14 kt casting will be covered with a very shiny layer of
pure 24kt gold.
As for the peroxide. The stuff you buy at the grocery wont do You
need the strong stuff that hairdressers use.
Again DO NOT try this. It’s safer to just plate it with 24kt gold.
Start with the boiling water. The steamer nozzle is one way to do
it. But please, after that, keep the nozzle out of the picture once
you’ve added the cyanide or peroxide. You don’t want to be spraying
any of the mix around the room, and once you add the peroxide, the
reaction generates it’s own additional heat. Not boiling again only
means it might take a few seconds longer. Also, be careful where you
point the beaker or pitcher. The reaction really does almost explode,
and can “burst” all over the place. Use a container much larger than
the volume of liquid you’re using. I used to use a plastic half
gallon pitcher to process a half cup or so of liquid, and even then,
often had some overflow to be caught in the much larger dishwashing
tub I was doing this in. The pitcher was angled so overflow would
stay within that tub…
Things to note: Even without boiling it again or initially after
adding cyanide, the reaction itself will give you at least a little
bit of cyanide in the steam/aerosols in the air. You do not want to
breathe that. At the least, it can give you a nasty headache. at
worst?.. So if you bomb (that’s what this is called, bombing), do it
with suitable very effective ventillation. Also, note that the waste
liquid when you’re done, contains some of your gold. You’ll want to
treat it like any other cyanide solution that contains valuable
gold. This is not so simple, though not all that complex either. Be
sure you know what you’re doing. Additionally, even if you’re not
worried about tossing a little gold away (!), you cannot just dump
that solution down the drain. Disposing of cyanide containing
solutions has to be done in accordance with local regulations.
With all that said, bombing can indeed be a useful process, if
you’re doing it right and observing needed safety issues. Things like
chains and detailed surfaces and even raw castings or highly
worn/tarnished things can be given a bright shiny 24K surface that’s
virtually impossible to get any other way. But given the risks and
fuss and bother to do it safely, along with just having and storing
the chemicals, I’ve totally switched to the much easier magnetic pin
tumblers, which brightens complex surfaces almost as well, though it
doesn’t give you the 24K color. I haven’t actually bombed anything in
almost 20 years, and do not miss the headaches at all.