Stainless vs carbon

There is a nasty grey coating on the silver surface which is  
 resistant to removal. I even thought at one point that the   
rubber in the tumbler was breaking down but that also seems   
unlikely. If the two types of shot are mixed I guess there is
no    easy solution to separating them ?<<

I’ve used carbon steel shot in a vibratory tumbler (it’s not a
flow thru) for years with no problem. I use household ammonia &
a small amount of burnishing soap. You might try cleanning the
shot with Draino (sodium hydroxide) & trying it again.

One way you might try to seperate the shot is with a magnet. If
your stainless is truely stainless, it’ll be non magnetic, carbon
steel isn’t.

However, there is alot of ‘stainless’ out there that has a high
carbon content & is magnetic. If you’re lucky, maybe your
stainless is STAINLESS

FWIW: The new high speed magnetic burnishers supposedly use
stainless pin’s, but I’ve never heard what the number of the
stainless alloy is/was. If it is a true stainless, magnetics
won’t work.

Good luck =