I searched the archives for this one, and it appears to be a shared
problem. I also asked around some industry people here, and there
seems to be a general degree of confusion about it.
Here’s the scene:
I casted a ring out of 14k gold and had no issues with it. I fluxed
with borax during casting, and everything came out fine. No cupric
oxide, no cuprous oxide. I did the melt with a propane torch (no O2).
After finishing, when I soldered on the prongs, a 15 second process,
the ring went pink all over. Except for the prongs, which were 18k
This happened to me twice. Both times I was using Handy flux, and
used it liberally, and the ring was entirely covered.
I’ve had firescale before when I was making ingots (I don’t have all
the right equipment, so sometimes I do overheat). This I’ve removed
with a 50/50 nitric acid / water bath. 3 second dip followed by steel
wool removes it no problem.
So between the Sparex and the nitric, anything on the item that
wasn’t supposed to be there would be removed.
This pink just will not come off. The tone is almost like it’s been
copper plated with a very thin layer of copper. I’ve used clean
pickle, so it’s not a contamination-by-iron effect, and it was pink
almost immediately after I hit it with the torch for soldering.
The best I could do was polishing and buffing, which has removed
about 70% of this stuff. The ring still has a pink tint to it. In
yellow light, you can’t see it (you could before) but in daylight it’s
In the archives, someone said to add peroxide to the pickle bath.
When I tried to buy the peroxide one supplier refused to sell because
I said I was going to add to the pickle (they said it wouldn’t do
They offered to bomb the ring for me as a favor, and told me to go
home and give it a finished polish, mount the stone, they would bomb
and that would be the last step. I did this, brought it back in, and
they then told me that after bombing I would have to polish and that
bombing only cleans the ring. I would have to polish again, at which
point the color would be uneven.
My understanding of bombing was that it removes everything that’s not
gold from the surface of the ring, leaving behind a 24k finish. I
said this to them, and they told me that I was wrong. I don’t know, am
I? I only read about bombing once a bit ago so I could be wrong.
Anyway, it bothered me that the story changed overnight, so here I am
with my finished, mounted polished pink ring, scratching my head.
I did go to another supplier and bought peroxide and added it to the
pickle. It did seem to help remove some, but without knowing what
kind of concentrations I should be looking at, or if it really
"officially" works, I can’t say for sure.
For the record, here is what I’ve tried:
(1) polishing (2) sparex (3) sparex with H2O2
result: between the three, removed about 70% of the tint
(4) nitric dip
What I can’t try because I don’t have the equipment:
(1) electroplating (2) electrostripping
Question: what the heck is this pink tint? It looks like copper, and
if it is, what mechanism is bringing it to the surface?
Anyone know a sure fire way of getting rid of it?