What is this stuff?

[daschnoz]

I was happily casting some 30 cal, 185gr boolits this weekend, and I was interrupted by the arrival of the wife with a car full of groceries. No problem. Wash hands, hump bags from car to house, put groceries where they belong, back to casting. Total time away from casting - about 15 minutes.

When I get back to the pot, there is an interesting mix of junk floating on the surface. Part of it is a greenish/yellowish colored substance that looks like dirt. There is also some dark red looking substance that has formed a crust on the top of the pot.

I skimmed this off and continued to cast.

What is this stuff? Is it impurities that finally had enough undisturbed time to float to the top, or is it an oxidized metal that is no longer in my alloy?

[Muddy Creek Sam]

If it was cleaned well during smelting it is Oxidized metal. Stir it back in.

Sam :D

[sqlbullet]

Green, yellow, dark red and 'crust' sound like a polymer of some kind to me.

Like Sam said though, if it was properly cleaned during refining, then it is metal oxide. Unless of course something fell into the pot in your absence....

[docone31]

Oxides, and sulfates, can stay in the melt untill they work their way to the top.
That is where fluxing comes in handy.
I have had that happen many times. My primary melting is not sufficient to remove the Oxides and sulphates. I started useing Kitty Litter on the top of my Lee Pro 20 pot.
I have not had any negative reactions from these being in the melt, but when it does surface, usually when I let the pot sit, the Kitty Litter absorbs it into the clay. I later will just turn the pot upside down when it is cool and the powder will fall out.
I do this about every six months.
I have found this stuff in my melt also.
Another indication of the merit of useing a seperate pot for melting the crud off the metal prior to casting.

[sagacious]

The melt likely got a little too hot in your absence. Those colors are probably antimony compounds, just part of the expectable dross. Was there any antimony in the alloy?

[daschnoz]

The melt likely got a little too hot in your absence. Those colors are probably antimony compounds, just part of the expectable dross. Was there any antimony in the alloy?

I don't know what the exact alloy was, but it is quite hard. I alloyed it 1:1 with WW, and it is still quite hard.

I would bet there is some antimony in it.

[Doby45]

Prolly some of your tin was in that too. I will get a thick scab on the top of my pot from time to time and I just stir it right back in with my wooden dowel..

[sagacious]

I don't know what the exact alloy was, but it is quite hard. I alloyed it 1:1 with WW, and it is still quite hard.

I would bet there is some antimony in it.
If it's hard lead, that dross is likely to be one of several common Sb compounds. Sb can form white, yellow, or red compounds easily. There's a post or two every month about "strange yellow powder" on someone's melt or melting pot. Probably Sb compounds-- nothing to worry much about. Good luck.