What's that orange crust?

[oldsalt444]

So I'm casting pistol bullets using COWW and a little 50/50 bar solder. Of course I flux the mix with a wooden dowel stirring well. Things are going well and it's time for a lunch break. I leave the Lee bottom pour pot at casting temperature and set the mold on top of the pot to keep it warm. When I return 30-40 minutes later, there's a thick orange crust built up on the top of the alloy. So I skim that off and continue casting. The bullets come out perfect, even a bit better than before. What is this crust and why doesn't it show up while I'm casting?

[megasupermagnum]

If it's an orangish-yellow powder, it was probably lead oxide. The most common cause is too high a pot temperature. It could be that your flux burned off and the lead was exposed to air.

[Winger Ed.]

Leave a pot sitting awhile and at different times, with different alloys, and you'll see a few different colors float up and make a 'skin'.
Gray, gold, sort of a mustard color, and purple are pretty common ones for me.

I figure it's mostly oxidation of the different metals in the alloy.
Stir it frequently, and either it stays in solution, or doesn't have a chance to form.

[Land Owner]

I don't understand

...flux the mix with a wooden dowel stirring well..

What material, not method, do you use to flux the alloy?

Flux is the addition of a catalyst (ex: wax, sawdust, cat litter, other) to the surface of the melted alloy, stirring it in for the purpose of binding with impurities, that make those easier to remove, AND to keep the oxidizing alloy components in suspension with one another.

[dondiego]

I don't understand

What material, not method, do you use to flux the alloy?

Flux is the addition of a catalyst (ex: wax, sawdust, cat litter, other) to the surface of the melted alloy, stirring it in for the purpose of binding with impurities, that make those easier to remove, AND to keep the oxidizing alloy components in suspension with one another.

He fluxes with the wooden dowel as he is stirring with it.

[imashooter2]

If you don’t have any dowels, your local home center gives away paint stirrers for free.

[centershot]

I don't understand

What material, not method, do you use to flux the alloy?

Flux is the addition of a catalyst (ex: wax, sawdust, cat litter, other) to the surface of the melted alloy, stirring it in for the purpose of binding with impurities, that make those easier to remove, AND to keep the oxidizing alloy components in suspension with one another.

It's been a while since college chemistry class, so forgive me if this isn't exactly correct. "Flux" is basically hydrocarbon of some type; some guys use sawdust, some wax, etc. Using a wooden stick of some type is no different than using sawdust, it's just sawdust in it's "solid" form. Works great, and smells better than burning wax.