I’ll just add a couple of items that I haven’t seen mentioned yet.
Since a vibratory tumbler was mentioned I assume the “barrel"
mentioned is really a hard plastic bowl. These are pretty much
bullet proof chemically so you’ve either got some serious solvents in
your system, or you’re using way too much of the soap (hence the
The rubber rotary type drums are especially sensitive to
detergents (which will coat your shot and pieces with a heavy coat of
dissolved drum goo) but I’ve always used a mild detergent soap in the
vibratory bowls with no problems at all. In any event, you might try
some Loretone powdered burnishing compound which is rubber drum
friendly and, one would think, would be even more benign towards the
hard plastic variety tumber bowls. Mix this product as you use it and
not as a stock solution as it seems to sour with age.
As for cleaning shot (mine is stainless), I found that a
teaspoon of Bon Ami kitchen polishing cleanser in with enough water
to just get a good action going in a vibratory tumbler cleans it up
beautifully - and fairly quickly. I imagine it would work for carbon
steel as well but there is not, too my knowledge, any rust inhibitors
in the Bon Ami.
There might also be a possibility that you are running your flow
through at an insufficient rate and the shot itself is abrading the
bowl, the residue of which then somehow is coating the contents.
Based on my experience, and your description, however, I would look
at the soap/burnishing compound you’re using first. I ordered a 25lb
box of so called burnishing powder from Swest recently only to find
"caustic chemical" labels on the box. After my disolving rubber drum
trip, I sent it right back.
I also think the manufacturers recommend too much of their
compounds. I cut it in half, saved $$ and got better results.