Greenish yellow dirt????????

[3006guns]

I'm smelting some linotype for some of the members on this forum. I've used this metal many times over the years without any problem, but this is the first time I've melted a large quantity. Equipment consists of a turkey frier burner, stainless pot, ladle and ingot molds.

Everything was going well, except the ingots were taking too long to cool, so I turned the burner output down a bit thinking I had the melt too hot. As I waited for the last pour to cool I looked into the pot and the surface was covered with a powdery green/yellow dirt looking mass. It would not melt back into the metal even with increased heat. I tried fluxing with no results.

Since I have quite a bit to pour, I stopped at that point until I get an idea of what happened. This is good metal and I don't want to damage it. Since lino is an alloy, is it possible that I caused a gravity separation of some sort from running too hot at the beginning? If so, I'll just call that batch junk and start over with a much lower heat output.

[3006guns]

I think I got my question answered. Evidently I DID get the metal too hot (first time with a turkey burner) and had an alloy separation as I suspected. Never happened with my electric bottom pour because I had better heat control. That first batch goes to the scrapper.........dang it!

[Matt_G]

3006guns
Where did you find out that is was excessive heat?
I was under the impression that lino was a true solution so to speak, and therefore not subject to separation in that manner.

I dug out my copy of Cast Bullets published by the NRA and read Dennis Marshall's article on heat treating lead alloys.
On page 119 he states:
"While there are several materials which may be added to lead to improve its strength, tin and antimony are at present the only practical alloying elements for cast bullets. When either of these is added to molten lead, a metallic solution is formed. It is a common misconception that because they are less dense than lead, antimony and tin may undergo gravity separation from the melt. Nothing could be further from the truth. The solution formed in this case is like that when sugar, salt, alcohol, or antifreeze is dissolved in water."

Could that green and yellowish crud be ink and other crap?
I guess I'm just not convinced that particular batch of alloy is junk. :veryconfu

[masscaster]

The greenish/yellow stuff is junk, not the alloy itself. i've had this on many occaisions over the years. It's just some impurities. Best to keep the heat low, skim alot of it off, give it a fluxing, reskim, and pour.
Save the lead.
masscaster

[.45Cole]

In the lyman casting handbook it says that black specks on the surface are tin particles, and to flux back into the mix. I think that many things will come into and out of solution, depending on the temp, elements involved, and concentration. Maybe if you could identify your constituents and get a phase diagram from some scientific lead site???

[carpetman]

I've always heard don't eat yellow snow. People do eat snow. Never heard don't eat yellow dirt--but I guess that's because people don't eat dirt anyways.

[DanM]

I have seen the greenish-yellowish slag during several sessions. Fluxing just produces more until you get it all out. I am pretty sure it is just unwanted crud that should be fluxed out and skimmed off....

[EMC45]

I've seen it too. I usually push it down into the mix a couple times then flux it. After that anything left in it goes to the skim pot.

[sagacious]

I think I got my question answered. Evidently I DID get the metal too hot (first time with a turkey burner) and had an alloy separation as I suspected. Never happened with my electric bottom pour because I had better heat control. That first batch goes to the scrapper.........dang it!
Yes, your problems were definitely caused by overheating. Despite constant claims to the contrary, MORE heat is often not always a good thing.

But the problem was surely not "alloy separation." The cause the overheating, and the result is high rates of dross formation. Fluxing at high-heat won't fix it. Only flux at low heat, and only pour at just high-enough a temp to get good pourability. Hotter than that can-- and will-- cause the problems you encountered. This is basic foundry practice.

That batch of linotype need not be scrapped. It is not permanently damaged. Add 1% tin back in, and flux at a low temp, and pour into ingots. Lesson learned, and no damage done. I have seen exactly what you described, and the batch can be reclaimed.

Hope this helps, good luck.

[3006guns]

Guys, I can't thank you enough......shoulda known the answers would be right here! It's just that I had never had that experience before, despite all the casting I've done over the years....at least not with that amount (about 4 tablespoons) and I was smelting about 40lbs. in one shot. Come to think of it, it might very well have been old ink and printing "crud" infused with the metal itself as it looked clean and shiney on the surface. I'll keep the kettle full of metal and break it down into ingots for future use. Again, thanks for relieving my mind!

[msw]

What were you fluxing with? I just had this happen with Wheel Weights using boric acid. My melt got to about 925!