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Tarnish problems while tumbling


#1

I’m new to this group so first let me say hello…

And now for the questions… (let the games begin):

I’ve been working on some mass finishing issues for tumbling glass
and metal at the same time in order to eliminate hand finishing of
pieces.

needless to say I am having some problems… when tumbling with
plastic media from Rio the glass gets slightly abraded, no problem as
this is easily refinished using a lap wheel and cerium oxide, brings
the glass back up just fine unfortunately some of the cerium oxide
gets trapped behind the glass pieces… this in itself is not a
major problem as we are using primarily opaque glass pieces so it is
unnoticeable…

however, when I return the pieces to the tumbler to burnish the
silver using mixed stainless shot and Rio deburring solution… there
seems to be a chemical or electrical reaction occurring that is
causing oxidation on the surface of the silver on testing the
solution after tumbling I get an approximate PH of 8

anyone know exactly what’s going on… I have the funny feeling
that the cerium is acting as an O2 donor for anodizing the
silver… could this be the case… and if so anyone got any
suggestions on how to eliminate this issue

thanks,
Jon P


#2
however, when I return the pieces to the tumbler to burnish the
silver using mixed stainless shot and Rio deburring solution... 
there seems to be a chemical or electrical reaction occurring that
is causing oxidation on the surface of the silver on testing the
solution after tumbling I get an approximate PH of 8 

Dear Jon,

I’m not sure this is the issue but part of your above statement
caught my attention. You stated your using deburring solution with
steel shot? Don’t, it’s simply not effective. Deburring solution is
engineered for abrasive media, not burnishing media. Burnishing is a
non abrasive step so use a burnishing compound, you should see much
better results.

I hope this helps.
Respectively,
Thackeray Taylor
Rio Grande Technical Support.


#3

Jon - Stainless steel runs best in a basic or alkaline solution - and
a pH of 8 is basic. What I would try is to use the burnishing
solution, rather than the deburring solution. And maybe if you
polished the glass after running the steel, instead of before, you
could eliminate the cerium oxide interference. Alternately you could
run the pieces in an ultra sonic to thoroughly clean them prior to
running the burnishing with steel. Or you could set the glass after
finishing the silver.

Judy Hoch