I am reluctant to brush with a brass brush because it scratches the surface.
One of the functions of brass brushing here is to burnish down the
fine silver so that it fills the microscopic spaces that you have
taken the copper out of. I’d suggest doing a lot of depletion/
pickling/burnishing steps, and doing a little very fine buffing at
the very end of the process.
M’lou Brubaker
Minnesota, USA
You need a really fine bristle (.003") brass platers brush
lubricated with soapy water this burnishes the surface instead of
scratching. This will leave a shiny reflective surface but not the
high polish that a buffing machine produces.
Jim
James Binnion
@James_Binnion
James Binnion Metal Arts
360-756-6550
I think you can burnish the surface without removing the fine
silver.
V.
I’ve done some enameling on sterling silver by bringing the fine
silver to the surface first so the enamel sticks and doesn’t change
color. I’ve flashed it in the kiln to bring the fine silver up.
Afterwards, I’ve polished (on a wheel) the silver to bring it up to a
high polish. I’m not sure what % of fine silver is left, but I’ve had
pieces that have not tarnished for years sitting next to the same
casting but not yet flashed that have tarnished. I’ve always assumed
that they’re not tarnishing because the fine silver is protecting
the sterling.
-a
Amery Carriere Designs
Romantic Jewelry with an Edge
www.amerycarriere.com
Afterwards, I've polished (on a wheel) the silver to bring it up to a high polish. I'm not sure what % of fine silver is left, but I've had pieces that have not tarnished for years sitting next to the same casting but not yet flashed that have tarnished. I've always assumed that they're not tarnishing because the fine silver is protecting the sterling.
Not if you hit them with a buffing wheel. The fine silver layer
“brought up” by heating and pickling is extremely thin the slightest
abrasion will remove it. This is why this kind of surface is finished
by brass brushing or burnishing not polishing. Many castings have
sulfur dioxide in their surface from investment breakdown which will
James Binnion
@James_Binnion
James Binnion Metal Arts
360-756-6550
James,
Not if you hit them with a buffing wheel. The fine silver layer "brought up" by heating and pickling is extremely thin the slightest abrasion will remove it.
Is there possibly another reason why my pieces are not tarnishing? It
actually doesn’t matter to me that the fine silver isn’t at the
surface, I’m just curious. It’s a bonus that there’s no tarnish, but
it’s not necessary. I think the bottom of your email got cut off!
-a.
Amery Carriere Designs
Romantic Jewelry with an Edge
www.amerycarriere.com
Is there possibly another reason why my pieces are not tarnishing? It actually doesn't matter to me that the fine silver isn't at the surface, I'm just curious. It's a bonus that there's no tarnish, but it's not necessary. I think the bottom of your email got cut off!
I was trying to say that the castings can tarnish rapidly due to
fine gas porosity but somehow cut it off when I sent it. When
investment breaks down due to overheating sulfur dioxide is
generated, this gas combines with the solidifying metal and causes
one form of gas porosity. The sulfur dioxide can end up being one
source of the sulfur that causes tarnish. Tarnish is a chemical
reaction between sulfur (or sometimes chlorine) and silver. If there
is a low amount of sulfur in the local environment then the silver
will not tarnish very rapidly and higher amounts cause more rapid
tarnishing. So you enameled pieces may not show signs of tarnish but
the cast pieces may be “self tarnishing” due to high amounts of
sulfur dioxide. It is really impossible to say why one of your pieces
tarnishes and the other doesn’t without a lot more and
analysis but all silver tarnishes when exposed to enough sulfur in
its environment.
Jim
James Binnion
@James_Binnion
James Binnion Metal Arts
360-756-6550