It seems to me that you could modify your process a bit and eliminate
the dirty stainless steel in the following way…
Apply your liver of sulfer before you run your castings in anything.
Then run your castings for at least 4 hours in each of the abrasive
media, medium and fine in a vibratory tumbler. This will clean off
the liver of sulfer on the high spots and it will stick better in the
low spots. You also now have much cleaner stuff to run in steel in
your rotary tumbler.
A couple of cautions - be sure to clean your work pieces very well
between each process. After each run of the steel, put on rubber
gloves, immerse your steel in hot water with Dawn. Agitate the
steel, and note your gloves. If they have black streaks on them, the
steel isn’t clean. Repeat with Dawn until the streaks go away.
Question: are you using a liquid with your steel specifically
designed for the process? There are many, but all have surficants,
lubricants and detergents. Plain old soap won’t do the job and will
result in some of the problems you are having.
Judy in Lakewood, Colorado where the fires have died down in the
mountains. Over 20,000 acres burned and more than 50 homes gone.