Today I was finishing up two necklaces, one 14k gold and one 18k
gold. I finished soldering them both, put them into a pickle that
I’ve been using all day for silver with no unusual results, and
pulled both pieces out to find that the 18k gold necklace had turned
a beautiful coppery pink. But not the 14k necklace. Huh?
I’ve gone through all the threads on Orchid I could find on this
subject and found some good on why this kind of plating
might have happened in other circumstances, but I can’t figure out if
it applies in my case.
My 18k necklace is just a simple handmade 18k pendant on a purchased
18k cable. I believe the cable is solid 18k, but now I’m not so sure.
Or could it be the clasp that was the problem? I hadn’t replaced the
commercial clasp yet, and part of it was indeed immersed in the
pickle.
The 14k necklace is a similar handmade pendant on a 14k chain and
also had commercial clasp still attached.
Also, I put the now-pink necklace into a solution of new, cold
pickle and hydrogen peroxide, with no change in color. It’s going to
be difficult to buff a cable…Should I burn it off? Or was my
solution maybe just not strong enough?
Hi, interesting - this too happened to me, but it was because the
pickle was saturated with copper from the silver. I did a solution of
nitric acide and water = Aqua Regia - to remove the “stain”.
The copper plating would most likely be caused by the steel spring
hidden inside the clasp. As to why the 14ct cable did not get plated;
possibly the 14ct clasp was not submerged, or the spring in the 14ct
clasp is stainless or more stainless than the spring in the 18ct
clasp. There are many different grades of stainless steel, some react
mildly in acid and others are completely immune to the acid. My acid
tongs are of the immune variety.
To remove the copper plating I would first remove the clasp, then
gently heat the chain in a soft bushy flame until the copper
oxidises. Pickle it, and finish by hand using a brass brush and
bicarb soda. Polish the clasp on the buffing wheel because heating
the clasp will anneal the spring. Electro stripping may be a better
way, perhaps someone will explain how.
If the clasp is not spring activated, then look carefully for a
gilt-over-chrome jump ring or fitting (it should be obvious after
the pickling as being extra cruddy), because chrome will also cause
the plating to take place when in the pickle.
I suggest using the hydrogen peroxide mixture hot. Keep an eye on
it. Remember that, surprisingly, it is a mixture that starts with
hydrogen peroxide. I add pickle until it starts to bubble. Remove and
rinse, and scrub off the sludge frequently until the pink is gone.
Aqua Regia is a mixture of nitric and hydrochloric acids not nitric
acid and water. What you made is sometimes referred to as a bright
dip and will indeed remove the copper plating but it also dissolves
the silver as well! Aqua Regia has little effect on high silver
alloys as the hydrochloric acid in it converts the silver to silver
chloride which is not soluable in aqua regia and stops the acids
action on the piece. The silver chloride formation also slows and
eventually stops the aqua regia action on 18k yellow gold and leaves
it coated with a whitish layer of silver chloride.
Jim
James Binnion @James_Binnion
James Binnion Metal Arts
Sarah, watch the solution while the necklace is in it – are there
tiny little bubbles forming on it and rising from it? If there are no
bubbles, the solution is not strong enough.
This is almost certainly the result of two things: the pickle has
dissolved some copper as a result of being used for some time (it
probably looks slightly blue), and you accidentally immersed some
iron with the gold pieces (possibly a steel spring in a clasp, or a
steel jump-ring). Fresh pickle won’t do this, even in the presence of
iron.
I once made some complicated earrings out of white gold chenier.
Since the chenier had to be bent to quite a small radius I originally
made it with a copper core that I thought could be dissolved with 10%
sulphuric acid, but it didn’t work; the copper appeared untouched
even after a day or so.
Although I’d read previously that a core of soft iron was
recommended I was also aware of the problem of iron causing the
copper to be deposited, so I tried an experiment; I left a loop or
two of the copper filled chenier in the acid and dropped an iron nail
in too. The iron fizzed a bit, but after several hours there was no
visible copper on the gold and the nail was visibly attacked so I
remade the chenier on a soft iron core and put it the acid again.
This time it worked; the iron was dissolved OK (took a day or so),
but to my surprise, the white gold got plated with copper.
From this I learned that the iron has to touch the gold for the
copper to be deposited. This would explain why one item was plated
and the other not; the one that was plated was touching the iron.
I found that 30% nitric acid removed the copper in a few seconds. I
put the acid in a small jar, took it outside into the garden,
suspended the earrings on a bit of nylon cord, and dipped them in.
They fizzed like a Selzer tablet for a few seconds, and when it
stopped I removed them - the copper was gone. I thought the nylon
wouldn’t be affected by the acid, but I was wrong. A few minutes
later the nylon just broke - but it had already done its job.
I found that 30% nitric acid removed the copper in a few seconds.
Since it is copper you want to etch away, not silver, wouldn’t it
make more sense to use ferric chloride, which etches copper and not
silver? Nitric acid etches silver like crazy-- why risk it?
I’m thinking that the spring clasp on the 14k chain was the problem.
I’m still stumped as to why the 14k didn’t plate, only the 18k, which
had a non-steel-interior bayonet clasp, not a spring clasp. Both
clasps were submerged. WHY would the 14k clasp plate the neighboring
18k chain, but not the chain it was attached to? A couple of you said
that only the gold touching the steel would plate, but there was no
steel touching the 18k. Yep, I’m seriously stumped.
Regarding old pickle, which a couple of people referred to, my
pickle was not old, not blue, and had been used only a couple of
dozen times previously. So I’m pretty sure that was not the problem.
So, now I’m going to take Cynthia’s advice and mix up some hot
H2O2/pickle solution and try again. Hopefully that will do the trick.
I’ll report back.
WHY would the 14k clasp plate the neighboring 18k chain, but not the
chain it was attached to? A couple of you said that only the gold
touching the steel would plate, but there was no steel touching the
18k. Yep, I'm seriously stumped.
If the chains were touching then that is all it takes, spring steel
touching 14k clasp/chain touching 18k chain will do it. However
there is spring material in a typical bayonet clasp.
Regarding old pickle, which a couple of people referred to, my
pickle was not old, not blue, and had been used only a couple of
dozen times previously. So I'm pretty sure that was not the
problem.
Pickle even used a couple of times will have enough copper ions in
solution to plate out.
So, now I'm going to take Cynthia's advice and mix up some hot
H2O2/pickle solution and try again. Hopefully that will do the
trick. I'll report back.
Don’t leave it in there too long as it will eat the spring
mechanisms in the clasps
James Binnion @James_Binnion
James Binnion Metal Arts
WHY would the 14k clasp plate the neighboring 18k chain, but not
the chain it was attached to?
Some 18KY alloys have a percentage of silver, so you may have gotten
the reaction on the 18K but not the 14K although I can’t say Its
ever happened to me.