A recent post rightly indicated that the best way to deal with
firescale is to not incur it in the first place. This is absolutely
correct. However, in our shop, in which we do a lot of silver
fabrication and repair,we use Prips Flux. Prips works equally well
on gold in those instances when high heat and/or multiple soldering
procedures require extra finish care. Prips has, in our years of
experience, never failed to prohibit firescale on silver when
properly mixed and applied. You may check the Orchid archives for
many past discussions on it and its componets. It is a Must for
any silversmith! Best wishes for a wonderful Christmas.
depends on the metal. if copper just put in the pickle for a few and
it will come off, if sterling the firescale is under the surface and
it has to sanded or filed off. if gold, usually its just a copper
plating and that can be sanded off same with brass. copper and brass
need to be in nitric and sterling and gold in sulfuric for pickle if
its hot(not boiling) it will work quicker
Here’s a trick I learned a long time ago - if you want to check if
you have firescale, place (hold) the object on a piece of white paper
and perpendicular to it- if there is any fire scale you will see the
purplish discoloration and can tell instantly where you need to
polish to get it off.
I work mostly in 18k yellow, and the result is a dark, lustrous
surface that looks like 24k.
Dear Doug, Would be kind enough to review your depletion technique.
I always felt that Ag atoms on the surface had to be desolved out,
and this does not occur with ordinary pickle.
I work mostly in 18k yellow, and the result is a dark,
lustrous surface that looks like 24k. Dear Doug, Would be kind
enough to review your depletion technique. I always felt that Ag
atoms on the surface had to be dissolved out, and this does not
occur with ordinary pickle.
This is really simple. I use an alloy that is 75% gold, 10% copper,
and 15% silver. After removing scratches, etc., I simply heat the
piece, allowing an oxide layer to form on the surface (will be
black). Then, I drop it in the pickle for a few minutes, burnish it
with a brass brush or in the magnetic finisher, and do this again a
couple of times. I use sodium bisulfate, but the traditional recipe
for this type of depletion pickle calls for a sulfuric acid and water
mix, used hot, with a “pinch” of sodium dichromate (the dichromate
acts as an inhibitor, and allows the pickle to only attack the
oxide). What is happening here is simply that the copper on the
surface is converted to cupric oxide, and this oxide is dissolved in
the pickle. The more copper in your alloy, the more fine gold will be
left behind on the surface. If you use an alloy of 75% gold, 24%
copper, and 5% silver, the alloy will be quite red, quickly oxidize
to a deep black when heated, and come out of the pickle looking like
24k. If you want it to look pink, you now have to remove the fine
gold with an abrasive. This alloy is also quite hard, so if you want
the look of 24k but need an alloy that does not bend easily…this is
it. Have fun with this, have a great holiday!
With regard to enriching the surface of gold-- I used the technique
Doug Zarube describes (the same as for sterling), but was not
satisfied with the results. Reasoning that the gold–14k in my
case–included silver as well as copper, I heated and pickled,
alternating between ordinary Sparex, and nitric acid, assuming that
the sparex would remove the copper, the nitric the silver. This
worked quite well–I was even able to reticulate the result. Hope
this is of use. --Noel