Identify zinc contamination in alloy

[lcclower]

OK, reloading for 40 years but just started casting.

How do you identify zinc contaminated alloy?

I am getting massive amounts of dross that's shiny lead colored, fluffy, like dipping ice cream off the top of the pot. i'm using sawdust to flux.

Also got a little metal stuck to a lee baloonimum mold. Can't pick it out with a toothpick. is that zinc, and do i need to put that mold on ebay, get twice the price, and order a new one?

TIA, LC

[fecmech]

When it's really bad the lead looks like oatmeal, lumpy and clingy. I contaminated 3 batches while smelting three 5 gal buckets of WW's a couple weeks ago. I skimmed two of them and while there is still some zinc in the mix after adding about 5% tin they cast ok. Incidentally I checked the ingots and they test a 19 BHN air cooled! The really bad batch I'm going to use for casting 12 ga slugs for my daughter to practice her self defense shooting with her pump slug gun. it's not going to make much difference at close range.

[GP100man]

There has been so much discusion on the subject that you could probably read for a week !!!

Use the search option & I bet ya get pages full of threads !!!

But the real test is in the castability of an alloy , it`ll never fill the mold corners out completely , no matter what !!!

[white eagle]

just because you get junk floating on the top doesn't mean its zink(unless you had some in your mix)
I just had a batch of pure that had the same symptom and my mix contained no zink what so ever

[lwknight]

Same here. I got something that made zinc looking crud on top and had ZERO surface tension. The normlly rounded edges were square and flat. Did the acid test and no reaction. The ingot is still dead soft anyway. Someday I willl get to the ( the real test ) casting test