Smelting heavily oxidized lead

[whisler]

Some years ago a friend and I got some lead from a college indoor .22 range. We smelted some and stored the rest in his shed in open 5 gal. buckets. He did some repairs on the shed and moved the lead outside where it got wet and oxidized badly. Today we tried to smelt some and it was a bear to say the least.

We started with a cold pot and heated until everything that would liquefy did. We fluxed heavily with both wax and cedar pet bedding,but still had lots of crud that would not melt. We skimmed it off and poured ingots but I know we are losing lots of lead because the scrap bucket (5 gal.) is only half full and very heavy. I know that the trash is from oxidation because this was very clean lead originally.

Does anyone have a good suggestion for smelting the rest of this lead without so much loss? Is there a better fluxing method than what we used? All help appreciated as we don't want to lose this lead what with the increasing difficulty of obtaining lead.

[olafhardt]

I would try less lead in the smelter and more flux and longer fluxing time.
I would try resmelting the flux also. Increasing the carbon in the flux with charcoal may help. The reactions are not instaneous so you may have to cook it longer.

[w5pv]

Don't know how much good it does but I always put the dross back in the melt and flux with the other melt.It seems that I don't lose as much that way.

[snuffy]

Just my opinion, but if you're getting a lot of oxidized dross, you're not hot enough. The melt should be hot enough so that when you drop wax into/onto the top of the scrap lead, it should flash to flame in only a few seconds. The cedar should smoke a lot and burn if you light it with a match or butane torch.

You didn't say what your heat source is, but it must be capable of getting the melt to 1000 degrees.

.22 lead is mostly pure, with a bit of antimony and tin, right around 8 BHN. You need to get it to a bare minimum of 800 degrees, 1K would be better.

Take that dross, get it REAL hot and flux with the cedar, and then some wax.

[whisler]

I'm pretty sure we were hot enough. We use a propane plumbers furnace and the bottom of the cast iron pot had a bit of red glow. The lead was already oxidized before we started. Some one on the forum once commented on using old motor oil for flux. I know this would be a smokey stinking mess but would it offer any advantage over what we were using? Or would charcoal be a better choice?

[dbosman]

Please be careful. Powdered lead oxides are dangerous.
Running the temperature of molten lead above 1112 degrees Fahrenheit is how one forms lead oxides for industrial processes.

[whisler]

Any comments on used motor oil or charcoal for this application?

[rr2241tx]

Considering the "red glow" in post 5 and the industrial process for making lead oxides in post 6, maybe you are too hot. Use a thermometer and go to about 800*F then give it a good fluxing with sawdust and call it good.

[DLCTEX]

Forget the oil and use sawdust for flux.

[whisler]

Just to be clear it was the outside bottom of the cast iron pot that had a bit of red glow not the lead. Thanks for all replies (and a PM).

[L Ross]

I was using waste motor oil for quenching oil hardened steel when a fire fighter friend gave me heck for it. He explained there are PBB flame retardants that are very bad for your lungs when you inhale the smoke. I have my best luck with soft wood saw dust. I also have some flux sticks left from an old print shop, I ration those for bottom pour pot use only.

Duke

[trixter]

If you can, use pine sawdust, the resins in it work to allow the crud to actually separate from the lead and float the junk to the top. I have been doing this for years and as far as i can tell my alloy is very clean. Also, get a thermometer. That made all the difference in the world to my smelting and casting.