Hi, Hoping someone can help me. I’ve recently have been having
problems with “shadowing” on sterling silver. When polishing, after
it is nice and shiny, there are dark spots on the surface. Not just
the polishing compound. They do polish off but I’m wondering why its
happening. I can’t recall having this problem in the past but I
usually use a tumbler if at all possible. I am using Grey Star
polishing compund. I don’t know if it is residual firescale and need
to pickle longer, or if the piece is getting too hot during
polishing or its the compound or what.
Please help -
Jenny in Minnesota where it is finally getting nice.
Sounds like firestain ( firescale, or those damn purple blotches)
from not having a good solid covering of prips flux or cupronil when
you soldered on the bead, or if they are cast it may be firestain
from the casting process. Either way it is a pain to get rid of .
You have to grind it off or plate over it. A simple way to cover it
(plate over it) is to raise the fine silver to the surface by
heating (fluxing it well of course) and pickling followed by brass
brushing do this several times and you will deplete the copper from
the surface of the piece leaving only fine silver behind . You can
then finish the bead and the firestain will be hidden. But you must
be careful when finishing as the fine silver layer is very thin and
you will polish right through it quickly with an aggressive compound
like greystar.
Jim Binnion
James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160
@James_Binnion
Member of the Better Business Bureau
If the shadowing looks dull or slightly purple it is fire scale.
Unfortunately it will have to be abraded off by heavy polishing
with tripoli. If the shadow is in a confined spot where you cannot
get to it with a large buffing wheel you might want to use a small
buffing wheel and tripoli or zam on your Foredom. It will take time.
The best bet is to not get fire scale when you solder. There are
several fluxes that can be used to cover the entire piece before
each solder step. They will prevent fire scale when used properly.
There is also Prips. The formula can be found in orchid archives.