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Thread: Zinc Removal with Sulfur Report

  1. #141
    Boolit Buddy
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    Did my best today. 300 pounds of zinc contaminated alloy. Respirator was a necessity. Stayed upwind, but got an ocasional tingle around the eyes, no repiratory issues though. Worked as advertised. Lost about 15 pounds of dross. I suspect some of that was lead as I was trying for super clean lead.

    When to stop fluxing with sulphur was my question. When I started having molten sulphur nuggets on the surface with no reaction, I fluxed with sawdust and wax, skimmed and poured into ingots. I’ll try casting and shot dripping this week. Report to follow.

    SO/ safety observer served hot cocoa during breaks. Hands washed, etc...(34 degrees)

  2. #142
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    Hi all, thought i would post my results from attempting to remove zinc from the wheel weights i melted down last week. I attempted to cast some 200 gr .308 boolits and there were wrinkles all over them. Didn't matter what temp the alloy was at or how hit i ran yhe mold i still got wrinkles and it wouldnt fill out at the sprue hole. I assumed i had zinc contamination. I went to my local Co-Ok and picked up 2 bags of sulphur powder. It is 99.5% sulphur and it is used as an insecticide for garden plants. I had maybe 60 pounds of ingots i needed to treat. I got set up with my propane burner and cast iron kettle i use to melt lead scrap. I used my 4" dipper to add the powder sulpher to the melted lead and the temp was almost 800 degrees according to my Lyman lead thermometer. I added the powdered sulphur and immediately it began to smoke heavily and bubble. I stirred the concoction and lifted lead from underneath the sulphur and poured it through the bubbling mess. After the smoke subsided there was a defined cake of hardened dross on top of the lead. I busted it into smaller chunks and removed it from the melted lead. I could tell a difference in the lead, it was more streaky instead of granular. After i scraped the pot good and spooned off the remaining slay, i addes another ladle full of the powdered sulphur. Again, i stirred and poured lead through the sulphur as it pyrolized into the burned cake of goo. I repeated this two more times for a total of four sulphur cleaning ventures. I lost a little less than 1/4 of the lead I started out with. After I poured the cleaned lead into bigots, i cleaned out my Pro Mag lead melted and added 7 lbs of the cleaned lead to the melted and set the temp to 750 degrees and allowed it to melt. After it was ready i heated the 200gr .308 mold by casting about 30 boolits. When the mold was ready, it threw some nice boolits, much better than the previous ones. Some came out really good and others had a small wrinkle on the nose. I use a Lee Harsness Tester to check the hardness of alloy and before the sulphur treatment they were BHN 10.4 and after the treatment they are BHN 8. I do not know if the sulphur treatment removed any antimony or if the initial hardness was from zinc, i don't know. This is my experience with this process. When i do it again, i believe i will heat the mix up to 650 degrees and skim any crystallized zinc off the top and sulpher flux, then take the temp up to 800 and sulphur flux. Might try the copper sulphate also.

  3. #143
    Boolit Master super6's Avatar
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    I just processed 30lbs of zinc contaminated lead with 99% pure sulfur. A friend gave me a bucket full of salt water sinkers awhile back that I thought were lead, I added to my lead pot about 3lbs of the weights and found out they were mostly zinc! After the sulfur treatment I had about 22lbs weight after skimming. I think I now have near pure lead, Antimony, tin, and zinc, gone! the lead is as soft as butter. I will add back tin and antimony
    Give me something to believe in. Poison
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  4. #144
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    Quote Originally Posted by Butterbean View Post
    Hi all, thought i would post my results from attempting to remove zinc from the wheel weights i melted down last week. I attempted to cast some 200 gr .308 boolits and there were wrinkles all over them. Didn't matter what temp the alloy was at or how hit i ran yhe mold i still got wrinkles and it wouldnt fill out at the sprue hole. I assumed i had zinc contamination. I went to my local Co-Ok and picked up 2 bags of sulphur powder. It is 99.5% sulphur and it is used as an insecticide for garden plants. I had maybe 60 pounds of ingots i needed to treat. I got set up with my propane burner and cast iron kettle i use to melt lead scrap. I used my 4" dipper to add the powder sulpher to the melted lead and the temp was almost 800 degrees according to my Lyman lead thermometer. I added the powdered sulphur and immediately it began to smoke heavily and bubble. I stirred the concoction and lifted lead from underneath the sulphur and poured it through the bubbling mess. After the smoke subsided there was a defined cake of hardened dross on top of the lead. I busted it into smaller chunks and removed it from the melted lead. I could tell a difference in the lead, it was more streaky instead of granular. After i scraped the pot good and spooned off the remaining slay, i addes another ladle full of the powdered sulphur. Again, i stirred and poured lead through the sulphur as it pyrolized into the burned cake of goo. I repeated this two more times for a total of four sulphur cleaning ventures. I lost a little less than 1/4 of the lead I started out with. After I poured the cleaned lead into bigots, i cleaned out my Pro Mag lead melted and added 7 lbs of the cleaned lead to the melted and set the temp to 750 degrees and allowed it to melt. After it was ready i heated the 200gr .308 mold by casting about 30 boolits. When the mold was ready, it threw some nice boolits, much better than the previous ones. Some came out really good and others had a small wrinkle on the nose. I use a Lee Harsness Tester to check the hardness of alloy and before the sulphur treatment they were BHN 10.4 and after the treatment they are BHN 8. I do not know if the sulphur treatment removed any antimony or if the initial hardness was from zinc, i don't know. This is my experience with this process. When i do it again, i believe i will heat the mix up to 650 degrees and skim any crystallized zinc off the top and sulpher flux, then take the temp up to 800 and sulphur flux. Might try the copper sulphate also.
    When I did it the goo was like lead colored taffy with big bubbles then it turned black. It seemed that about half of the melt turned into that mess. Is that what your's looked like?

  5. #145
    Boolit Master WRideout's Avatar
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    Quote Originally Posted by Butterbean View Post
    Hi all, thought i would post my results from attempting to remove zinc from the wheel weights i melted down last week. I attempted to cast some 200 gr .308 boolits and there were wrinkles all over them. Didn't matter what temp the alloy was at or how hit i ran yhe mold i still got wrinkles and it wouldnt fill out at the sprue hole. I assumed i had zinc contamination. I went to my local Co-Ok and picked up 2 bags of sulphur powder. It is 99.5% sulphur and it is used as an insecticide for garden plants. I had maybe 60 pounds of ingots i needed to treat. I got set up with my propane burner and cast iron kettle i use to melt lead scrap. I used my 4" dipper to add the powder sulpher to the melted lead and the temp was almost 800 degrees according to my Lyman lead thermometer. I added the powdered sulphur and immediately it began to smoke heavily and bubble. I stirred the concoction and lifted lead from underneath the sulphur and poured it through the bubbling mess. After the smoke subsided there was a defined cake of hardened dross on top of the lead. I busted it into smaller chunks and removed it from the melted lead. I could tell a difference in the lead, it was more streaky instead of granular. After i scraped the pot good and spooned off the remaining slay, i addes another ladle full of the powdered sulphur. Again, i stirred and poured lead through the sulphur as it pyrolized into the burned cake of goo. I repeated this two more times for a total of four sulphur cleaning ventures. I lost a little less than 1/4 of the lead I started out with. After I poured the cleaned lead into bigots, i cleaned out my Pro Mag lead melted and added 7 lbs of the cleaned lead to the melted and set the temp to 750 degrees and allowed it to melt. After it was ready i heated the 200gr .308 mold by casting about 30 boolits. When the mold was ready, it threw some nice boolits, much better than the previous ones. Some came out really good and others had a small wrinkle on the nose. I use a Lee Harsness Tester to check the hardness of alloy and before the sulphur treatment they were BHN 10.4 and after the treatment they are BHN 8. I do not know if the sulphur treatment removed any antimony or if the initial hardness was from zinc, i don't know. This is my experience with this process. When i do it again, i believe i will heat the mix up to 650 degrees and skim any crystallized zinc off the top and sulpher flux, then take the temp up to 800 and sulphur flux. Might try the copper sulphate also.
    I hope that taught those bigots to watch what they say in public.
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  6. #146
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    For those of you still scratching your heads... It took me a while to figure out. OP used the word "bigots" instead of "ingots"...classic spell check mangle.
    Last edited by Traffer; 06-24-2019 at 01:29 PM.

  7. #147
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    I have a small batch of pewter and one of solder both zinc contaminated. Went from 9% Zn to 6% with two fluxings. So I figured about 3% reduction for two passes of sulfur fluxing. Did 4 more passes and will send samples to BNE to have them tested.

    Yes thick black/dark grey sludge for the dross I skimmed off. No idea of temperature. Hot, did in the fire pit far from the house or garage. Wood fire, small cast iron pot nestled in the coals. Spoon wired to long handle and stir stick of dried pine about 3/4 inch thick.

    Will be interesting to see how much zinc is reduced and what it did to the tin amount of the alloys since both were high tin to start with.
    .
    Scrap.... because all the really pithy and emphatic four letter words were taken and we had to describe this source of casting material somehow so we added an "S" to what non casters and wives call what we collect.

    Kind of hard to claim to love America while one is hating half the Americans that disagree with you. One nation indivisible requires work.

    Feedback page http://castboolits.gunloads.com/show...light=RogerDat

  8. #148
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    Quote Originally Posted by RogerDat View Post
    I have a small batch of pewter and one of solder both zinc contaminated. Went from 9% Zn to 6% with two fluxings. So I figured about 3% reduction for two passes of sulfur fluxing. Did 4 more passes and will send samples to BNE to have them tested.

    Yes thick black/dark grey sludge for the dross I skimmed off. No idea of temperature. Hot, did in the fire pit far from the house or garage. Wood fire, small cast iron pot nestled in the coals. Spoon wired to long handle and stir stick of dried pine about 3/4 inch thick.

    Will be interesting to see how much zinc is reduced and what it did to the tin amount of the alloys since both were high tin to start with.
    .
    Interested to see how it turns out. Question...Could you use a larger dose of sulfur per firing?

  9. #149
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    Quote Originally Posted by Traffer View Post
    Interested to see how it turns out. Question...Could you use a larger dose of sulfur per firing?
    I'm covering the top of the melt with sulfur to some depth, then stirring it in as it melts. I suppose I could use more sulfur if the pot was larger or the amount of lead alloy was less.

    I was using a couple of older roughly 10 to 20 lb. capacity cast iron pots. Have a heavy metal bail handle so I can hook them in and out of the fire even when full. I think the pots might have been for a plumbers lead melter. Their size determined the total amount of sulfur I could apply. I was using a 1.5 pound capacity ladle mostly full wired to a long wood handle, call it a large open hand worth of sulfur. I used more for the 2nd and 3rd fluxing than I did originally when I had samples XRF tested that showed the 3% drop from 2 fluxings.

    Not sure if it will clear out all the zinc or not. May be the high tin will interfere, or not. Will see.
    Last edited by RogerDat; 06-28-2019 at 11:15 AM.
    Scrap.... because all the really pithy and emphatic four letter words were taken and we had to describe this source of casting material somehow so we added an "S" to what non casters and wives call what we collect.

    Kind of hard to claim to love America while one is hating half the Americans that disagree with you. One nation indivisible requires work.

    Feedback page http://castboolits.gunloads.com/show...light=RogerDat

  10. #150
    Boolit Master super6's Avatar
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    https://en.wikipedia.org/wiki/Lead_s...ead_processing. Seems you need 1000+ and some other chems. I know my sulfur rescue was At least 1000 degrees.
    Last edited by super6; 07-20-2019 at 03:23 PM.
    Give me something to believe in. Poison
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  11. #151
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    Quote Originally Posted by super6 View Post
    https://en.wikipedia.org/wiki/Lead_s...ead_processing. Seems you need 1000+ and some other chems. I know my sulfur rescue was At least 1000 degrees.
    Yup, when they process galena or lead ore with lots of sulfur, they use a process known as "roasting". It is not something that can be done at home. BUT the percentage of sulfur and other "impurities" they have to deal with is, I believe, way higher than what we are dealing with.
    The roasting consists of mixing coke with the ore "and other stuff" and introducing air or oxygen into the bottom of the huge furnace: from wikipedia:
    Oxidizing roasting
    Oxidizing roasting, the most commonly practiced roasting process, involves heating the ore in excess of air or oxygen, to burn out or replace the impurity element, generally sulfur, partly or completely by oxygen. For sulfide roasting, the general reaction can be given by:

    2MS (s) + 3O2 (g) = 2MO (s) + 2SO2 (g)
    Roasting the sulfide ore, until almost complete removal of the sulfur from the ore, results in a dead roast.

  12. #152
    Boolit Buddy
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    The gases have a high percentage of sulphuric acid,be careful, doesn’t take much exposure for bad things to happen!

  13. #153
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    Quote Originally Posted by RogerDat View Post
    I'm covering the top of the melt with sulfur to some depth, then stirring it in as it melts. I suppose I could use more sulfur if the pot was larger or the amount of lead alloy was less.

    I was using a couple of older roughly 10 to 20 lb. capacity cast iron pots. Have a heavy metal bail handle so I can hook them in and out of the fire even when full. I think the pots might have been for a plumbers lead melter. Their size determined the total amount of sulfur I could apply. I was using a 1.5 pound capacity ladle mostly full wired to a long wood handle, call it a large open hand worth of sulfur. I used more for the 2nd and 3rd fluxing than I did originally when I had samples XRF tested that showed the 3% drop from 2 fluxings.

    Not sure if it will clear out all the zinc or not. May be the high tin will interfere, or not. Will see.
    Sample "Sulfur Solder"
    Pb = 67.8%
    Sb = 0.5%
    Sn = 30.3%
    Zn = 1.4%

    Sample "Sulfur Pewter"
    Pb = 5.4%
    Sb = 6.6%
    Sn = 81.0%
    Cu = 2.0%
    Zn = 5.0%

    I think the results establishes removing zinc from high tin alloy is a dubious proposition. Both started with ~9% zinc The solder started at 40% Sn and lost 10% Sn and most but not all of the zinc. Brought it down to 1.5% The pewter being nearly all tin the sulfur was only able to remove less than half of the zinc to get down to 5%.

    Both samples got the same process so I would have to attribute the difference in amount of zinc removed by the sulfur to the differences in the alloy.

    I think the zinc has an affinity for tin that fights bonding or reacting with the sulfur for extraction. I don't doubt sulfur is more effective at pulling zinc from plain lead or COWW's. And taking some tin with it.

    I guess the stuff might be good cast as round ball for slingshot ammo....
    Scrap.... because all the really pithy and emphatic four letter words were taken and we had to describe this source of casting material somehow so we added an "S" to what non casters and wives call what we collect.

    Kind of hard to claim to love America while one is hating half the Americans that disagree with you. One nation indivisible requires work.

    Feedback page http://castboolits.gunloads.com/show...light=RogerDat

  14. #154
    Boolit Grand Master popper's Avatar
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    Sulfur takes out tin, zinc and a lot of stuff. It is also very soluble in lead so you get that funny sticky solidus stuff. Then it turned onto black powder most likely zinc sulfate (tin sulfate is more brown). Don't inhale the powder! Sulfur content can be reduced by heating to just at liquidous, solubility is minimum there. lead sulfate is created when current is applied.
    Whatever!

  15. #155
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    Quote Originally Posted by leadman View Post
    Anyone been brave enough to continue with the experiments?
    I'm trying to get the (tin and/or antimony out of my lead) I want pure lead for cap and ball black powder pistols. but I do have powdered sulfur and I'll try some more with the sulfur. and yes, I've worked in a a sulfur recovery unit at gulf oil in Port Arthur many years ago. and I know how flamable that is and how bad it stinks.

  16. #156
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    Quote Originally Posted by pakmc View Post
    I'm trying to get the (tin and/or antimony out of my lead) I want pure lead for cap and ball black powder pistols. but I do have powdered sulfur and I'll try some more with the sulfur. and yes, I've worked in a a sulfur recovery unit at gulf oil in Port Arthur many years ago. and I know how flamable that is and how bad it stinks.
    You'd be better off to sell the Sn/Sb lead and buy from a known source of pure.

  17. #157
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    you ain't wrong, and today is sunday, I'll start looking monday!

  18. #158
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    Quote Originally Posted by dondiego View Post
    You'd be better off to sell the Sn/Sb lead and buy from a known source of pure.
    Yup...look for possible trades....AND PERHAPS RUN AN AD ON CRAIGSLIST OR FACEBOOK MARKETPLACE. You could very well get lucky and find someone within driving distance who would be glad to trade hard for soft.

  19. #159
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    Had approx 15 lbs of Lyman #2 lead in the pot, threw in 5 battery connectors, must of been zinc. Turned the whole pot into mush. Sulfur worked perfect, just stay upwind of the fumes. Thanks to all here for their knowledge and help.

  20. #160
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    I prefer using copper sulfate when I have to do this, it adds a little copper to the lead which makes it more elastomeric.

    Fumes are nasty, you'll only "accidentally" breathe them once

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