Hi all - I consistently have the problem of 14 K gold discoloring to
a pinkish tint after heating. It is very annoying and I don’t know
what to do about it. I was told it was my flux - Dandix, but I’ve
since changed to Batterns and it hasn’t helped.
I know I can sand it off, but a lot of times it is inaccessible.
I’ve thought about just switching to 18K thinking there would be
less copper in it to affect the color. I wanted to check with all of
you first. By the way, I’m usually soldering gold to sterling -
don’t know if that affects it. Thanks in advance - Sarah
Sarah, If you are already aware of this, then I apologize for
restating it, but it sounds like contaminated pickle. Could it be
that you have introduced iron into the pickle solution? Are you
possibly leaving on binding wire or using steel tweezers ? Jerry in
Kodiak
Hi Sarah, The pinkish color on 14K gold is due to heat which causes
a copper oxide to form on the surface – in other words, it’s fire
scale. A good flux will help but if you overheat your pieces, the
oxide will form regardless.
To get rid of it you can 1) abrade it, 2) strip it with acids, or 3)
mask it by depletion gilding, which is what I usually do. If you’re
not familiar with depletion gilding, it’s a method of bringing fine
gold to the surface to cover the fire scale. Heat the metal till the
entire surface turns black (not so much, of course, as to unsolder
anything) and throw it in the pickle while hot (not red hot, but then
you shouldn’t be getting it red hot during this process anyway). The
black oxide will be stripped by the pickle and eventually (after
repeating this procedure 3-4 times), you’ll be left with a coating of
deep yellow, pure gold on the surface. Note: You wouldn’t want to
use this technique for a ring or any other piece that is subject to
a lot of friction, since the pure gold layer is not deep and can wear
off.
As for 18K – go for it! You will not have the fire scale problem,
the color will provide a greater contrast with the sterling, and the
18K has a higher melting point which means less risk of meltdown!
Beth
Hi Sarah… As you have been told the pink is copper you are bringing
up to the surface of the alloy where it will oxidize.
This will help… remember that silver will draw heat away from the
joint quickly…if you heat just the joint you are putting a lot of
heat on the gold part, that I assume is smaller than the silver part.
Heat the silver as well. Coat well with boric acid. Dissolve as much
boric acid as possible in methyl hydrate. Dip the articles to be
soldered in it and ignite the wet articles to burn off the alcohol.
This will leave a coating of boric acid that will turn into a water
soluble glass as it is heated. This glass will keep oxygen from the
surface of the metal. ( it comes off easily in the pickle) Most often
the pink colour is caused by a flame that is too oxidizing. The
excess oxygen in the flame is a major cause of this problem. Often
more oxygen is used in the soldering process to get enough heat to
cause the solder to melt. A neutral flame is best and if the heat is
not enough, then use a larger flame, remembering to supply heat to
the whole object being soldered not just the solder. 18kt will also
get fire scale, but it is a little different in colour. I promise you
that 14 kt can be soldered without the pink colour. If you need any
further just ask… Franklin
We have previously had this issue and are having it again. We
purchased yellow gold from our metal supplier, have melted once, was
fine, melted again and now has turned pink. Any thoughts on the
subject…
Look to the history of black pearls and consider it rare and market
as such.
Ok, not very helpful. Or… Maybe. historically things like that
have worked.
Christopher Lund
Neurascenic - Industrial Design
We have previously had this issue and are having it again. We
purchased yellow gold from our metal supplier, have melted once,
was fine, melted again and now has turned pink. Any thoughts on the
subject..
It may be that the copper in the yellow gold is coming to the
surface. You can remove it by either sanding it down or running it
through a supper pickle bath (hot pickle + peroxide). It has worked
wonders for me!
Best of luck,
Christine
christinebossler.com