Does this look like zinc contamination?

[Comfy]

Initially I was thinking it was zinc contamination, but after reading some threads about the purple color being a symptom of a too-hot pot, I'm not so sure. These were unsorted COWW and I never saw the thermometer go past 600. I did, however take the thermometer out after scraping out all of the clips and junk wheel weights. I experienced a purple oatmeal-like substance forming on top of the melt.
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[Traffer]

Doesn't look like zinc to me. Usually that color is Tin coming out (not really a good thing) But I would just skim that stuff off the melt and move on...not give it another thought....too much to think about...Keep it simple. This is something they did at camp fires in the 1830's we don't NEED to make it more coplex...I leave that for the guys who are pushing the limits with pressures and speeds with fancy alloys. (That is interesting but way past my education.

[44Blam]

When you melt that ingot, flux a couple times and keep it coolish. Maybe you can get some of that good metal back. :)

[Comfy]

When you melt that ingot, flux a couple times and keep it coolish. Maybe you can get some of that good metal back. :)

It seemed to work, I had to scrape off quite a bit, but the ingots look much better now.
I think what happened initially was due to a high percentage of steel COWW. Once I had taken all of those and the clips out, the temperature of the lead in the pot was allowed to sky-rocket.

Anyways, I think I'll be sorting my wheel weights from here on out, cause I have a feeling I lost a few pounds of good alloy.

[blackthorn]

Doesn't look like zinc to me. Usually that color is Tin coming out (not really a good thing) But I would just skim that stuff off the melt and move on...not give it another thought....too much to think about...Keep it simple. This is something they did at camp fires in the 1830's we don't NEED to make it more coplex...I leave that for the guys who are pushing the limits with pressures and speeds with fancy alloys. (That is interesting but way past my education.

The OP specified the melting of unsorted wheel-weights. I sort of doubt 1830 era casters had much beyond pure or almost pure lead, certainly there was no zinc in their melt.

[bangerjim]

PB when overheated can turn colors of the rainbow just like that. That is just normal. Looks over-heated to me, but still good to go as you stated above.

Today you ALWAYS sort WW's due to the high count of Zn and Fe ones being used. I quit messing with COWW's several years ago when the ratio of good Pb to garbage to amount of work got totally out of whack. WW's are not worth my time anymore.....even when free. I have found that when it comes to WW's today free is definitely NOT free!

banger

[Traffer]

The OP specified the melting of unsorted wheel-weights. I sort of doubt 1830 era casters had much beyond pure or almost pure lead, certainly there was no zinc in their melt.

I meant that in general we don't have to overthink it. Something as simple as one batch of lead with a bunch of mush on top is something I wouldn't even give another thought, Skim it off and keep going. It really can be simple.

[jimb16]

I sort as best I can, but some zinc always seems to escape notice. As a result, I melt the wheel weights at a temperature 50-100° below the melting point of zinc. The zinc weights just float on top and are easily removed.

[gifbohane]

If you have already cast an ingot and you are sure that you have zinc in it, is there a way to remove it?

[Traffer]

If you have already cast an ingot and you are sure that you have zinc in it, is there a way to remove it?

Here is a thread on the subject of using sulfur. I have tried this and for me it "seems" to work but if you are not sure if there is zinc or how much... it can be a real head scratcher. Best to read a lot of this thread first.
And above ALL be careful of the FUMES from this stuff. I doubt if I will ever do it again for that reason...Make sure you do it outside, upwind of the pot AND USE a gas mask. Don't take chances with it This stuff is NOXIOUS and TOXIC...http://castboolits.gunloads.com/showthread.php?62957-A-possible-way-to-remove-zinc-from-molten-lead

[OS OK]

I always see that color when I'm smelting dead soft lead, the deep blues & purples swirl in the top of the pot like an oil slick but when the ingots have cooled the lead can have a darker blueish tone but I've not seen it collected on top of an ingot like that before.
I use a thermometer and keep my lead under 725ºƒ.

[brad925]

Zinc melts at about 787F. If you didnt get over 700 its not zinc.I find alot of garbage in WWs so could be that.

[blackthorn]

An easy way to determine if there is zinc in your alloy is to place a drop of Muriatic acid on the surface of your ingot. If there is zinc, the acid will bubble/foam. Muriatic acid can be found at pool supply retail outlets. You will likely have to purchase at least a liter/quart which is several lifetime supplies for our use.

[lightman]

It seemed to work, I had to scrape off quite a bit, but the ingots look much better now.
I think what happened initially was due to a high percentage of steel COWW. Once I had taken all of those and the clips out, the temperature of the lead in the pot was allowed to sky-rocket.

Anyways, I think I'll be sorting my wheel weights from here on out, cause I have a feeling I lost a few pounds of good alloy.

I'm glad that it seemed to clean up for you. I always sort my weights. I smelt in pretty large batches and the temps on the bottom of the pot can easily melt zinc. And I don't want to contaminate 400# of lead. Once you have sorted a bucket of weights it gets easier. You develop a system that works for you and you get a feel for it.