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Thread: A possible way to remove zinc from molten lead

  1. #101
    Boolit Mold
    Join Date
    Oct 2017
    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. ****ed 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
    Join Date
    Nov 2015
    outside of Sand Springs, N.E. OK
    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
    Boolit Master AllanD's Avatar
    Join Date
    Feb 2008
    southern edge of the Poconos
    "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 Master popper's Avatar
    Join Date
    Jun 2011
    Just add clean alloy until the Zn is low enough to cast well.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check