Tumbling gunk problem

[mycrstuff]

That looks like you used the Lyman media with rouge. It is media with a red polishing compound saturated into the corncob. It leaves red marks on all of the brass. You need to wipe it off with a rag.

I have also had the same effect by leaving brass in the tumbler for a week. The polishing compound turns to a goo and sticks to the brass. The only difference is that it is a thick black goo. It is very difficult to get off. Make sure to empty the tumbler as soon as you are done.

[divingin]

That looks like you used the Lyman media with rouge. It is media with a red polishing compound saturated into the corncob. It leaves red marks on all of the brass. You need to wipe it off with a rag.

That's jewelers rouge; iron oxide powder. Makes a nice shine, but the Lyman media (at least the box I was given) is way overtreated, leaving the red powder all over everything.

For a new batch of walnut or corncob, about a quarter teaspoon of rouge should work pretty well; just enough to color the media without having extra rouge wafting off in the breeze.

FWIW an auto cutting wax works pretty much the same, and leaves a bit of protection on the brass as well.