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Goldfill doesn't appear yellow anymore


#1

Hi all- recently I made some goldfill and Argentium byzantine chain
and now have two questions for the more technically minded. First, I
heat hardened in toaster oven 400* for 2 hours - the goldfill seemed
slightly more reddish, the silver usually turns black (clean,
dedicated toaster oven and Pyrex dish). Any thoughts of why this
happens? Pickling then tumbling takes care of it, but this time I
forgot to set a timer. The chain tumbled for around 3 hours, and now
the goldfill is indistinguishable from the silver. I have tried
pickling, superpickling, polishing and cleaning the shot in flat
Coke before retumbling (Rio suggestion). Still extremely difficult
to distinguish the two metals. What have I done, and how can I undo
it without picking apart 50" of chain? Polishing w/ 3M wheels seemed
slightly more effective than anything else, but didn’t do much. Rio
tech thought the chain may have become coated w/ steel from the
shot. Any other thoughts of what might have happened, and/or how to
undo it? I appreciate any thoughts you might have, and thank you for
taking the time to help.

Blessings,
Sam Kaffine


#2
Rio tech thought the chain may have become coated w/ steel from the
shot. 

I think it’s more likely the goldfill parts of the chain became
coated with silver from the silver parts of the chain. Steel is so
much harder than the metals in the chain, it won’t have rubbed off.
But soft silver might have rubbed off on the harder goldfill, if the
goldfill surface were even slightly rough, and maybe even if
polished. If the goldfill is now lightly coated with silver, try a
brief, dilute (I’d try around a 10% solution), nitric acid pickle.
Test on a very small portion first. If the goldfill is intact, it
won’t be dissolved, though it might discolor. The silver would be
dissolved, though, getting you back to goldfill and silver colors.
You might then have to start over with cleaning if the acid
discolored the goldfill. Be careful with tumbling dissimilar metals
together. If you can buff/clean with mechanical manual means, like a
brush, 3M bristle disk or buff, you avoid those problems, but with
those methods, it can be difficult to reach all surfaces, and if
significant amounts of the metal remain uncleaned, then it will be
harder to tell the difference in colors sinch much of the surface
areas will still look too much alike. Good luck. This, by the way, is
one place where magnetic pin finishers are superior.

The tiny pins work fast enough, and get into all the crevices, to
burnish your metal, meanwhile your piece is not rigorously burnishing
itself against itself, the way it might do in a rotary tumbler with
standard steel shot.

Peter


#3
Pickling then tumbling takes care of it, but this time I forgot to
set a timer. The chain tumbled for around 3 hours, and now the
goldfill is indistinguishable from the silver. 

I’m only guessing here, but is it possible the heating for 2 hours
at 400 followed by tumbling in hard steel shot for 3 hours simply
demolished the gold on the gold fill chain? You’s then be left with
the base metal (probably brass?) innner.

Janet


#4
I'm only guessing here, but is it possible the heating for 2 hours
at 400 followed by tumbling in hard steel shot for 3 hours simply
demolished the gold on the gold fill chain? You's then be left
with the base metal (probably brass?) innner. 

Perhaps, but keep in mind that gold filled metal is not an extremely
thin gold layer the way gold plated would be. It’s a distinct
seperate layer of metal, laminated during manufacture to the base
metal. Unless heated to temperatures where the gold layer would
actually alloy, or melt, or over long periods of time diffuse into
the base, the low temp treatment described shouldn’t have done more
than oxidize that layer. And steel shot is not actually abrasive. It
should not have actually removed any metal unless done dry or without
suitable lubricant/tumbling soap/etc.

Peter Rowe