Other Considerations
I've not been in the polishing business long, and I don't run big batches in my vibrator. I'm using cob and some Cabela's agent. I did notice that it would take a longer time to get the cases polished. I also tend to run overnite a lot. Probably a wonder there is any brass left.....
As the media darkens, I have to add a little more brightening agent. Then, a load of cases would actually get a darkened appearance after a half hour or so. I figured that was the absolute end of media life. I figure I won't let it get that black in the future.
And, I got to thinking, (wondrous occurence), there must be a lot of lead in the 'black' stuff growing in the media. So, when the actual black dust started showing up, I figured it was time to dump. I'm pretty careful not to spill it, create any more dust than necessary, and don't handle it any more than necessary. I don't have a separator tumbler, and don't think I will get one. I use gloves to pick cases out of the bowl. I guess I'm getting paranoid in my old age.
FWIW, -West