lee production pot-yellow powder contaminant

[Silicon Wolverine]

OK i pulled my lee production pot out for the year and it promptly started to plug up on me. when i got all the lead out there was alayer of yellow powder on the floor of the mold and chunks of it blocking the drip hole. it was a PITA to get it all out and i ahent got the pot workin right just yet, any idea what this stuff was? the only thing i melt in the pot is pre-drossed WW lead. it looked like sulfur powder but didnt smell at all.

SW

[eli]

What flux are you using?

Eli

[idahoron]

Was the last lead you poured very soft lead? Ron

[454PB]

I'm betting it's sulphur. I once melted down a bunch of "pure" lead that contained some old concrete anchors, that's where mine picked up the sulphur. In the old days, they used lead and sulphur to anchor machinery.

[Silicon Wolverine]

the flux im using is frankfort arsenal. always been good before. all the lead i cast is WW with no exceptions. the only unknown contributor was a batch of lead that had been cast in pop cans but it all casted clean with no problems. this was all WW i melted myself last fall. i got it all out (eventually) and got it working. one of the guys i work with thought maybe it was arsenic used in casting the WW.

SW

[Southern Son]

I have had the same crap turn up in my 4-20 and 10 pound lee. I have only ever put certified 99.9% pure lead and tin from a foundry into the pots. I did notice that it only happened when I let the pot get too hot. How hot are you running?

[yondering]

I had the same thing turn up on the top of the melt in my 4-20 the other day. Mix was clean ww's +2% tin, and I had just cleaned the pot right before that melt. I was using the bottom pour, so wasn't stirring the melt at all, and after 20 minutes or so found a bunch of yellow powder and slag stuff on top. Some of the slag fluxed back in with sawdust, but the yellow powder wouldn't. Really curious what it was.

[GSM]

Lead oxide?

http://en.wikipedia.org/wiki/Lead(II)_oxide

[idahoron]

I have only seen it in pure soft lead. I also have only seen it when it was WAY hot. Ron

[Silicon Wolverine]

im running the pot set on 8 right now. its a hair to the hot side for casting but it works the best for me.

SW

[Bent Ramrod]

There's a yellow lead oxide called Litharge. It further oxidizes to a red version called Minium (which looks like rust) and finally to a dioxide, which is brown.

If you have some glycerol (glycerine) around, a mixture of this plus litharge makes a pretty good cement.