Originally Posted by
Butterbean
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.