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Thread: A possible way to remove zinc from molten lead

  1. #101
    Boolit Mold
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    An update. I am learning as I go.
    The slightly "wrinkled" bullets I thought might be polluted with zinc were sized and then weighed and are right on spec. And they are relatively soft, virtually identical to previous "clean" batches. I suspect I was casting at way too high of a temp, as some of the wrinkled bullets dented/ deformed when they hit the soft board tabletop i drop on to (yes, i dont drop into water). They were evidently still semi molten coming out of the mold.

    I couldnt bring myself to discard 50# worth of ingot, even though I was sure it has zinc in it. I did not want to get into sulfur, so i tried again with the smelt pot but at a much lower temp. It took a while to bring it to a molten state, but then I immediately reduced the flame once it had melted down. As I stirred, quite a bit of silver-grey oatmeal formed at the surface. After quite a bit of diligent skimming, I had quite a pile of zinc-like material in the discard pile. Probably 5-7 lbs. Crunchy brittle oatmeal. It is nowhere near as heavy as lead would be, so I am confident in what I removed. As a test, I cast about 50 swc from the pot so i could hardness test. Damned if they were not the most beautiful silver. Weight is correct. Hardness test in the vice was spot on. The rest of the pot i cast into ingot cupcakes, and they are the right color, no galvanized sparkle, and they "thud" on the floor, not bounce. yes i drop the cupcakes and listen/watch. I do need a life.
    I consider the evening a success. And some lessons learned: more heat is not better, avoid mystery metals, wrinkles are the fault of the person casting, not the metal.
    Last edited by spqr; 10-18-2017 at 11:07 PM. Reason: typos

  2. #102
    Boolit Master Oklahoma Rebel's Avatar
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    that oatmeal is probably antimony, keep the heat up. a cold alloy and a cold mold make for wrinkles. if the weight is right it probably don't have much if any zinc in it so ya don't throw it away. get a thermometer and keep the alloy at 675-700 and after a few throwbacks your mold will warm up, wait a second or two after your sprue hadens before you cut it. just make notes of what works and what doesn't, you'll get it! good luck-Travis,oh, that stuff you skimmed, pour muriatic ( hydrochloric acid) on it. if it fizzes it is zinc, if it don't it is antimony and you need to flux it back in. if it ends up as antimony pm me and i'll let you know how to get it back in.
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  3. #103
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    "flowers of sulfur" is more technically known as "sublimed sulfur", aka sulfur condensed from vaporized (converted to gas form) sulfur, it is basically "Distilled" sulfur and is the purest form generally available in commerce.

    Nice to know that it can be used to strip Zinc from a melt, in my case especially convenient as I have a cardboard canister of the stuff (30some pounds)

    In many parts of the world it is simply collected in "flowers" form as it collects on cool surfaces near Volcanic Vents , geysers and fumaroles.
    Last edited by AllanD; 11-08-2017 at 05:41 PM.

  4. #104
    Boolit Grand Master popper's Avatar
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    Just add clean alloy until the Zn is low enough to cast well.
    Whatever!

  5. #105
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    Quote Originally Posted by Southron View Post
    I went to the Sanders Lead Company in Troy, Alabama a few years ago. They have an industrial tower/bui9lding that looks like a cracking tower found in oil refineries. One of the Engineers told me that they bring in scrap lead and then heat it up to 2300 Degrees Fahrenheit and separate ALL the various metals from the lead.

    They sell their pure lead in 60 pound ingots and will actually give you a computer print out of all the metals in it. Their "Pure" lead is around 99.96% pure if I recall correctly.
    I need to check this place out. Sounds like a really neat experience.

  6. #106
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    spgr .. sounds like you are on the right track ..
    before long you will be a expert
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  7. #107
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    Quote Originally Posted by amosfella View Post
    Something similar is used in refining. Zinc is added in the refining process. Gold and silver are very attracted to lead, much more so than the Iron sand in which they are usually found. Zinc s added in the molten state after the iron is removed and melted in, as zinc is around 3000 times more attracted to gold and silver than to lead. The zinc then forms a dross on the top as the pot cools, and is skimmed off. Then the zinc is then boiled from the silver and the gold and recovered for reuse... Charcoal or coke is used to rid the lead of the zinc.

    If it were not for the usual of amount if Silver found in Lead Ore it would be financially Impractical to mine or refine lead ore.

    The Silver extracted during the smelting/refining process pays for the entire effort and any refined Lead produced is 100% profit... all due to the fact that Silver is 3000 times more attracted to Zinc than to Lead. any Gold or Platinum recovered is a "gift from God"

  8. #108
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    I think I got lucky by not really knowing what I was doing, but, the electric coil I use to heat the pan to melt down my wheel weights gets just hot enough to melt the lead but not the zinc. Saves me the trouble if I miss a few in sorting.

  9. #109
    Boolit Master
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    Will an infrared thermometer work on a smelting pot? My analog thermometer is too short to be very useful away from the casting pot.

  10. #110
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    your tin and antimony, assuming that there IS any in WW anymore, is on top, so skimming will remove it and you need it for 9mm, at least, and magnum loads. I use a ladle and a propane fired furnace, so keeping the top of the melt occluded will not work for me.

  11. #111
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    Quote Originally Posted by caffe View Post
    your tin and antimony, assuming that there IS any in WW anymore, is on top, so skimming will remove it and you need it for 9mm, at least, and magnum loads. I use a ladle and a propane fired furnace, so keeping the top of the melt occluded will not work for me.
    Metals don't separate like oil and water. It is a true solution like salt and water. There may be a little Sn/Sb oxidation on the surface and the hotter the melt the more oxidation. Add some wax or sawdust and mix well.

  12. #112
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    Quote Originally Posted by caffe View Post
    your tin and antimony, assuming that there IS any in WW anymore, is on top, so skimming will remove it and you need it for 9mm, at least, and magnum loads. I use a ladle and a propane fired furnace, so keeping the top of the melt occluded will not work for me.
    ????????? where did you learn from ??????????

  13. #113
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    Quote Originally Posted by dondiego View Post
    Metals don't separate like oil and water. It is a true solution like salt and water. There may be a little Sn/Sb oxidation on the surface and the hotter the melt the more oxidation. Add some wax or sawdust and mix well.
    Thank you for helping steering this back to reality. These conversations can go sideways quickly and end up promoting nonsense. Let's keep these things in the realm of reality.

  14. #114
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    Quote Originally Posted by Cosmic_Charlie View Post
    Will an infrared thermometer work on a smelting pot? My analog thermometer is too short to be very useful away from the casting pot.
    I don't have an IR thermometer but I have read that the shiny surface of the melt interferes with the IR meter which gives invalid results.

  15. #115
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    I had a 60 pound smelt go South because a serving platter I thought was pewter has some zinc in it. I used sulphur and sawdust, kept the heat up and it cleaned up great. Did it outside on a day with a steady breeze. Managed to do it without a respirator but the little I did breath in convinced me not to go without one next time.

  16. #116
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    Quote Originally Posted by spqr View Post
    An update. I am learning as I go.
    The slightly "wrinkled" bullets I thought might be polluted with zinc were sized and then weighed and are right on spec. And they are relatively soft, virtually identical to previous "clean" batches. I suspect I was casting at way too high of a temp, as some of the wrinkled bullets dented/ deformed when they hit the soft board tabletop i drop on to (yes, i dont drop into water). They were evidently still semi molten coming out of the mold.

    I couldnt bring myself to discard 50# worth of ingot, even though I was sure it has zinc in it. I did not want to get into sulfur, so i tried again with the smelt pot but at a much lower temp. It took a while to bring it to a molten state, but then I immediately reduced the flame once it had melted down. As I stirred, quite a bit of silver-grey oatmeal formed at the surface. After quite a bit of diligent skimming, I had quite a pile of zinc-like material in the discard pile. Probably 5-7 lbs. Crunchy brittle oatmeal. It is nowhere near as heavy as lead would be, so I am confident in what I removed. As a test, I cast about 50 swc from the pot so i could hardness test. Damned if they were not the most beautiful silver. Weight is correct. Hardness test in the vice was spot on. The rest of the pot i cast into ingot cupcakes, and they are the right color, no galvanized sparkle, and they "thud" on the floor, not bounce. yes i drop the cupcakes and listen/watch. I do need a life.
    I consider the evening a success. And some lessons learned: more heat is not better, avoid mystery metals, wrinkles are the fault of the person casting, not the metal.
    Keep it up...you are learning the same way I did and most of us here. I never throw away stuff ...later it may come to be useful. One fyi:
    IF you find that your molds are not filling as well with your "cleaned lead" Add about 1% tin or pewter. Tin can be pulled out when you try getting other stuff out like the zinc stuff you got. But it doesn't matter at all if your bullets are still filling the mold. Tin IS ONLY NEEDED when you cannot get get good fill (or if you are an expert and using it to help get stuff like copper and antimony to play well yadayaya. Only the high pressure guys mess with that.
    PS I don't water drop either. I have a towel folded up in a box that I drop them on...gotta be cotton... They hit and don't deform.

  17. #117
    Boolit Man
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    Fertilizer. Sulphur for gardeners, cheap.

  18. #118
    Boolit Mold
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    Quote Originally Posted by gidgaf View Post
    I would like to remind folk, as is was mentioned, that sulfur is commonly used as an insecticide. As simple as flowers of sulfur, in a box, with a wick. You will have bugs falling from the sky- or at least the ceiling. Make sure you are not downwind, and have lots of ventilation. Lots and lots.
    Sulphur isn't actually an insecticide but combined with other chemicals it is used in insecticides. sulphur is most commonly used as a soil amendment to adjust ph levels.

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