My solution for black residue has been to use two sets of two white
tumblers. The first contains the Rio Grande clean cut plastic media
and I use deburring compound solution in those. The second set
contains stainless steel shot and I use Rio’s burnising compound for
those. When I use a patina or the silver is quite tarnished, I begin
with the first set of barrels and change the solution if it becomes
dark and black and continue in short units of time until clear. Then
I transfer the silver pieces to the stainless shot and tumble as
needed for polishing.
The burnishing compound is not a cleaning media. The deburring is a
cleaner. Perhaps the black grease stuff could be dealt with by a two
step process. It has solved my problem very well. I do have to clean
my steel shot with ammonia occasionally. I’m tempted to try Judy’s
Coke method as well.