I've been casting for several years now but I am using pure lead for black powder for the first time. My question is related to the ingots I melted the lead into. I melted the lead down in the pot in the same fashion as my wheelweights, i.e. same burner, heat etc...

What happened was I have some ingots with beautiful colors, almost like case hardened steel. What are the colors? Is this a reflection of impurities, or did I use too much heat or not enough?

Those with experience please pipe up I am very curious. Thanks

I get this occasionally, and suspect it may be trace tin oxidizing on the outside. Another alternative could be the natural arsenic that occurs in native lead and is nearly impossible to remove all traces of in the smelting process. This can only be fully removed in a carefully controlled smelting, as too hot will cause permanent attachment of molecules, and for most any purposes, this purity isn't necessary.

I'll see if I can find my info from the old Mines of Spain, and the St. Louis smelter for more on this.

I think what you are referring to is called "frosting" where the lead looks like new steel. I believe that it comes from too high a casting temperature.

Rainbowing. That's all I know. Frosting is when it looks like it has an off-white coating on it.

Underclocked is right. The colors are a rainbow effect, frosting is when I am casting bullets, these are ingots.

Some of my local cronies tell me this is nothing to worry about but simply trace metals such as copper showing themselves.

This explanation seems plausible since the lead did come from telephone wire sheathing.