Melting lead - crazy colors

[wolvesdad]

I've been saving up Lead to scrap for for five years. I hardly come across any, an occasional tire weight, or some bullets, or something like that.
Well, we were on a fossil hunting trip, and came across a bunch of bullets and other lead scrap and copper scrap, and it got me motivated to melt some:
http://youtu.be/JbUHlh-0870
I think it was only after I started melting the tire weights that I started getting the yellow blue and purple colors.

Has anyone else seen this before? Do you know what metal in the mix is causing that?

Anyway, it was pretty, and I just thought I would share.

[Market Harmony]

Tin and bismuth maybe

[Kurr]

try salt, sawdust, borax, as a flux to do the reduction, parafin to flux an form a barrior anp prevent oxidation.

[johnbrickner]

Either of you ever think of starting an alchemy 101 class? Might pick up an apprentice or two.

[natsb88]

The colors come from bismuth. It's the primary metal in a lot of lead-free bullet alloys. It's also in a lot of low-temp alloys and lead-free pewter. It's 86% as dense as lead and non-toxic (or at least non-toxic enough) so it gets substituted for lead more and more. Costs a lot more than lead though.

It also works well WITH lead. Unlike most metals that shrink when they cool, bismuth actually expands 3% when it solidifies. In the right ratios you can get low-temp alloys that don't shrink. They used to be popular for casting type face for printing presses.

You can do a eutectic alloy with lead and bismuth that melts around 250 degrees and holds a constant volume whether its solid or liquid. That means you can use it as a cooling fluid in a closed system without having to manage major volume (pressure) fluctuations. Ideal for nuclear reactors because it also absorbs very little radiation. The Soviets experimented with it in some nuclear subs and there are some modern reactor designs that call for a lead-bismuth-eutectic cooling system.

It also has a very cool natural crystalline structure

[wolvesdad]

Haha, awesome! I had seen YouTube videos of people making super cool bismuth crystals. But I didn't think of it here. Ao some of the bullets I melted were bismuth alloy, not lead!? Neat.

[natsb88]

some of the bullets I melted were bismuth alloy, not lead!?

There may very well have been a lead-free bullet in there. They are usually 10% - 12% tin with the rest bismuth. Could also have been from a wheel weight. Bismuth was used in some earlier lead-free wheel weights before they came up with cheaper alternatives. Could have been in just about anything really if somebody was playing around with a low-melt alloy.