Crust forming on top of pot.

[mto7464]

Was casting along today, running hot and pouring good. It was a short session off about 1/2 hour. Near the end of my session I noticed a crust had formed on the top of my lead. It was almost 1/8" thick and kind of a dirty yellow looking stuff. I broke up into chunks and I tried to flux it but nothing happened as far as getting rid of the crap. I skimmed it off and dumped it in my coffee can. After it cooled I looked at it and it seemed to have some lead or tin in it since it was fairly heavy. I was using wheel weights with some tin added. Any ideas on what it was?

[bobthewelder]

I call it wheel weight crap! I get the same from some of my ingots. Maybe we didn't get all the WW crap off during smelting?

[longbow]

It is most likely "dross" or lead oxides. When the lead is heated and especially if it is kept at high heat you will get some oxidation and dry lead oxides (and maybe other oxides as well) will form a dry dross on the surface.

Try not to breathe it in as it is bad stuff and can be quite dusty. Also wash up after casting and especially after handling anything with dross on it.

Longbow

[mto7464]

perhaps tomorrow I will sprinkle some ashes on top to keep the oxidation down and see if that helps

[Shuz]

perhaps tomorrow I will sprinkle some ashes on top to keep the oxidation down and see if that helps

Another suggestion to avoid oxidation is to place a small layer of new kitty litter on top of your melt. Works great for bottom pour pots!

[NVcurmudgeon]

Save that dross. When it accumulates to say a coffee can full, flux it with Pat's California Flake Flux. It will surprise you how much good metal can be recovered.

[mto7464]

I turned down the temp and sprinkled some ash on top and that took care of it. I think I must have been running way too hot and burning my tin out of the mix.