Zinc Removal with Sulfur Report

[arcticbreeze]

Well I got up this morning in search of sulfur and found some. So I ran home set up my smelting pot and turkey fryer and started melting 40 of my 80lbs of zincified lead. Warning, Warming, Warning Sulfur is combustible and did ignite after all the moisture sizzled out and the fumes are real bad. I was up wind with a nice easy breeze but some swirreled around an hit me. It was an acid phosgene type smell and my nostrils burned for about 10 minutes. Good news is it does seem to have worked. After doing all of this I melted some of the lead into my bottom pour pot that I had just cleaned out real well so as not to re-contaminate and casted some of the pettiest boolits I have in a long time. Here are some pics of what came out of 40lbs of lead and some boolits from that lead. The slag/Zinc that came out weighed 4lbs 9oz.

http://castboolits.gunloads.com/picture.php?albumid=30&pictureid=1320

http://castboolits.gunloads.com/picture.php?albumid=30&pictureid=1319

http://castboolits.gunloads.com/picture.php?albumid=30&pictureid=1322

http://castboolits.gunloads.com/picture.php?albumid=30&pictureid=1321

[R.M.]

Them are some good looking bullets. I'd say you've solved the problem.
Thanks for the report. I know a good many of us can reclaim our contaminated alloy now.
How did it affect the hardness? Did it just remove the zinc, or did it remove some of the tin and antimony also?

[sciguy]

Arcticbreeze,

How much sulfur did you use of the whole operation? How much lead were you able to retrieve from the original 40 lb.?
It would be useful to develop some rules of thumb so as to not waste sulfur, over do the stink factor, etc..

Thanks for being a brave early experimenter.

Hugh

[testhop]

i use sulfer for pepper plants.
i buy it in 5 lbs bags at the farmers assotion. cheep

[GP100man]

it certainly looks as if it worked !!
I`ve been doing the hi temp cool down & skim off thing .
at what temp do ya add the sulpher???

Thanks for the report!!

[hiram]

It might be a good idea as a precaution to do an initial fluxing with sulphur to clean zinc out in case there is a small amount in there you don't know about.

[Trifocals]

Initially, this sounds great! Where did you come up with the idea/info to try this? As long as the sulphur is not pulling out the tin & antimony this should be a great fix for zinc contaminated lead. More info please.:drinks:

[arcticbreeze]

Trofocals

The idea came from a post from Sciguy

http://castboolits.gunloads.com/showthread.php?t=62957

As far as the amount I used 12oz total but I put probably about 3-4oz at a time until the reaction stopped. My experiment was pretty unscientific. I kind of went in to it already convinced it wouldn't work. I did not use a thermometer but I added the first batch when it was slightly slushy. I believe this would have been a temp at which the lead was molten and any zinc over the 1.6 percent soluble amount would still be non-molten. I did not use any resin after but did flux with beef tallow after. (My neighbor thought I was grilling steak) However I believe that step is not crucial to the zinc removal. I believe I could have fluxed with any carbon material at that point. Anyone that is going to try this I would suggest using a 6-8ft long 1x2 to stir with as I did. There did appear to be some moisture in the sulfur but it stayed on the top and did not sink. I did not attempt to stir it in until all of the sizzling stopped. While stirring was when it ignited. The fumes did seem to be pretty toxic so please be careful. As far as the amount of lead I only weighed the skimming so I would assume that was my only loss in weight. As far as tin loss I don't know but the castability dramatically improved so I think it was insignificant. But even if I lost some it was still better compared to the problems casting lead with zinc in it.

Marc

[DLCTEX]

From the whiteish ?(is that a word) appearence of the boolits I'd guess the 2% of zinc that will alloy with lead isa still there. In my experience that amount does no harm and may even be helpful. As stated, this is just a guess.

[castingagain]

Good Thread ! Whiteish is a word, I use frosted,have been told caused by wrong temp and/or sb going to surface of mold when cast.
I need a little help also if that's possible. I melted 50 lbs diver "tank" weights,(10 lbs. each) had No froth and maybe,4 oz. skim total, very,very low skim weight. Weights scratched with finger nail, cast good for no tin added but heres the problem.
.50 cal mold that drops 388 grains consistent with pure pb,1% tin now drops 356 grains? and still pretty soft?
dangest thing unless there is a WHOLE lot of tin and little if any SB
I only buy pure sheet but couldn't pass up the price on these. I know any type of ballast weights could contain anything and these didn't have the real dark (old) lead look. they were un-tarnished persay.
any ideas?
Thanks in advance for your time!
Dan

[peter nap]

Great Post!!!!!!!

[geargnasher]

Looks like this could be an excellent subject for a Sticky.

Thanks to Sciguy for posting the idea and Arcticbreeze for the first Grand Experiment (with nice pics!). This may prove to help a lot of people turn their doorstops into boolits!

Just need a little bit more research, I think I could establish some additional scientific conclusions, specific percentages, before and after lab analysis, etc. if I could get, say 1,000 pounds of zinc-contaminated WW alloy donated to me for testing and shooting purposes!:kidding::kidding:

Gear

[Freischütz]

Does this method produce better results than one achieves through holding the temperature below zinc's melting point and skimming off the zinc dross?

[deltaenterprizes]

A physics teacher I spoke with about this said sulphuric acid( Battery acid) would work to identify zinc wheelweights. The zinc would react the lead would not.

[rockrat]

Careful when burning sulfur. I would use a respirator. Your slag should contain zinc sulfate.

[mcooper]

A physics teacher I spoke with about this said sulphuric acid( Battery acid) would work to identify zinc wheelweights. The zinc would react the lead would not.


Maybe muratic acid would let you know as well.

[docone31]

Muriatic acid will not produce the same reaction.
Drain cleaner, Rooto, is the best pure sulphuric acid found in hardware stores. Battery acid is diluted.
You should be able to digest the zinc with the Rooto. The remaining "sponge" will be a more pure lead.
I am not sure, but other elements will also digest out of the alloy as well.
Heat, by specific gravity, will seperate but not completely remove the zinc. Acids will remove the elements. If any other elements are digested by the acids there are other methods that drop out individual elements.
With silver, Karo corn syrup drops out pure silver after processing. Go figuire.

[Wayne Smith]

I need a little help also if that's possible. I melted 50 lbs diver "tank" weights,(10 lbs. each) had No froth and maybe,4 oz. skim total, very,very low skim weight. Weights scratched with finger nail, cast good for no tin added but heres the problem.
.50 cal mold that drops 388 grains consistent with pure pb,1% tin now drops 356 grains? and still pretty soft?

Dan

Dan, lead is the heaviest and softest component. The heavier the boolit from a known mold the more lead and the less of lighter elements. Castability can be somewhat of a measure of tin. If the mold doens't fill out, or the base doesn't fill out, this suggests it needs more tin or more heat if you want a soft boolit. When my camera is charged and I have a few minutes I'll do a tutorial on my most problematic mold, my 457122. Heat balance is the issue with this one.

[Springfield]

I've put Muriatic Acid on some slag I thought had some zinc in it and it sizzled pretty good.

[inuhbad]

Excellent information!

[acsteve]

hydrochloric acid reacts much faster than sulfuric acid with zinc. Infact, zinc+HCl reacts to produce lots of hydrogen gas. So be careful working in closed areas.

[13Echo]

Muriatic acid is hydrochloric acid. Draino is sodium hydroxide, a very strong base, not an acid Battery acid is sulphuric.

Jerry Liles

[Stove_Pipe]

I've put Muriatic Acid on some slag I thought had some zinc in it and it sizzled pretty good.

Hmm, wouldn't that give off Hydrogen?

[geargnasher]

Muriatic acid is hydrochloric acid. Draino is sodium hydroxide, a very strong base, not an acid Battery acid is sulphuric.

Jerry Liles

The Doc said "Rooto", not "draino". Draino is Lye. Rooto is sulfuric acid.

Muriatic acid is a certain percentage solution of hyrochloric acid (diluted).

Gear

[felix]

Percentage is about 35 percent. ... felix

[geargnasher]

Thanks, Felix.

Gear

[leadman]

Anyone been brave enough to continue with the experiments?

[oscarflytyer]

Just picked up a bucket of WW from the tire place. As I was emptying my carry bucket, I noticed that there was a large amount of the stick on WWs.

Does anyone know - are the stick ons Zinc? Guessing they may be. If anyone knows for sure, I would appreciate it. Thanx

[arcticbreeze]

Just picked up a bucket of WW from the tire place. As I was emptying my carry bucket, I noticed that there was a large amount of the stick on WWs.

Does anyone know - are the stick ons Zinc? Guessing they may be. If anyone knows for sure, I would appreciate it. Thanx

The stick ons are most likely pure lead. Squeeze them with a pair of side cutters and you will know right away.

[arcticbreeze]

Anyone been brave enough to continue with the experiments?

I was debating on it. I was thinking about taking 2 zinc weights and mixing it with say 40 lead weights and then taking 1/2 of the mix and performing the whole procedure. Then taking the 2 samples and sending them to Rotometals for analysis. I have not decided if it is worth the $158.

[badgeredd]

Just picked up a bucket of WW from the tire place. As I was emptying my carry bucket, I noticed that there was a large amount of the stick on WWs.

Does anyone know - are the stick ons Zinc? Guessing they may be. If anyone knows for sure, I would appreciate it. Thanx

Use the side cutter method to check the stick-ons. About 20% of the stick-ons I have gotten recently WERE zinc. I'm also running into a lot more Fe stick-ons but they're pretty easy to spot as they seem to be shaped like little rectangle blocks.. I've had several zinc stick-ons that look the same as lead weights, so I suggest you use care with the stick-ons.

Oddly I haven't been getting very many clip-on zincs, but many more Fe clop-ons.

Edd

[oscarflytyer]

Sounds like nothing is absolute! Guess I will get to drink a lot of beer as i sort thru 6 gal of WWs! Thanx

[montana_charlie]

"Of particular interest to the bullet caster are calcium, aluminum and zinc -- all of which are difficult to reduce and all of which cause casting problems if present in any significant amount (they muck up the surface tension of the alloy and prevent the alloy from filling out the mould properly). As the sawdust chars, it can be thought of as a kind of activated carbon. Both the lignin's of the original sawdust and the oxygenated sites of the activated carbon are very effective at binding metal ions like calcium, aluminum and zinc. Thus, the advantage of sawdust is that it does both jobs, returning the tin to the melt and removing the problematic impurities. Sawdust has the added benefit of being free."
http://www.lasc.us/FryxellFluxing.htm

CM

[Bulltipper]

I used this method this week and it worked well. I did use a respirator and it was fine unless you really get a strong whiff. I would add this info to anyone trying this, Let the sulpher mix sit after you have stirred in your sawdust or flux. My first batch i removed the slurry as soon as the sawdust stopped smoking. I think I may have removed more lead than was necessary. The second batch I allowed to sit a little bit (3-5 min) and the slag formed a kind of hollow crust with lots of pretty colors. This crust was a lot lighter than the first batch. My boolits then came out of the melt much better looking and my melt pot only had a very light skin of purple on the top after the process instead of the heavy oatmeal and colors.

[grumman581]

The stick ons are most likely pure lead. Squeeze them with a pair of side cutters and you will know right away.

In my last batch of wheel weights, I had some stick-on ones that were steel.

[richbug]

I went to the feed store yesterday. a 50# of 100% sulfur was $29. That ought to last me a while. If the weather cooperates I plant to try this next week.


Now if I could only find saltpeter that cheap.

[trooperdan]

Dang Rich, what was that store? It is about $1.50 a pound in 25-50 pound lots around here!

[Rotometals]

If you mail in the samples together We will test up to 5 different pieces for the one flat rate of $69
http://www.rotometals.com/Metals-Analysis-XRF-Testing-s/59.htm




I was debating on it. I was thinking about taking 2 zinc weights and mixing it with say 40 lead weights and then taking 1/2 of the mix and performing the whole procedure. Then taking the 2 samples and sending them to Rotometals for analysis. I have not decided if it is worth the $158.

[grumman581]

I was debating on it. I was thinking about taking 2 zinc weights and mixing it with say 40 lead weights and then taking 1/2 of the mix and performing the whole procedure. Then taking the 2 samples and sending them to Rotometals for analysis. I have not decided if it is worth the $158.

I would hazard to guess that the end result is that it doesn't matter if you have zinc or not in your alloy if you are able to cast good bullets with whatever you have. Of course, I suspect that once you have zinc in your alloy, the likelihood of you casting good bullets is somewhat reduced... I would be interested in hearing about people who have tried casting with alloys that were significantly zinc contaminated and they were using a very hot pot... If you get it hot enough, does the zinc-lead alloy still have problems with fill-out?

[cuzinbruce]

Interesting thread. Made me get out my copy of "The Handbook of Commercial Bullet Casting" by Paul Moore. He uses sulfur to remove COPPER. For metal contaminated with zinc, aluminum or calcium, he says the removal process is difficult and dangerous and declines to give further details. Says it is too easy to generate highly toxic fumes. His suggestion is to dilute contaminated metal with good metal. Start with a ten to one ratio.
His method for refining the metal before casting is to dry dross with sawdust, then clean with caustic, sodium hydroxide at 700-800 degrees. Be careful as sodium hydroxide is hygroscopic (adsorbs water). He puts it on the top of the melt and leaves it until melted, without stirring. Stirs after it has melted. Finally removes the caustic with charcoal. I haven't tried this yet but be careful.
Bruce

[richbug]

Dang Rich, what was that store? It is about $1.50 a pound in 25-50 pound lots around here!

Mccartney's Feed and Hardware, Fredonia PA. Little Mom and Pop type place, they cater to a bunch of Amish, apparently they use it for chimney cleaning among other things. Also supposed to be good for raspberry bushes when mixed with wood ashes and powdered limestone.

[Ed-WI]

If you play with the acids, keep some baking SODA within reach. It neutralizes most common acids. It also reacts violently with acid if added too fast. Rub or pour it on yourself if you get splashed, never pour into the acid except a pinch at a time, maybe. And yeah, the fumes will seal yer fate especially hydrocloric HCl. That stuff will put you on your knees gasping.

I need the pure lead for RB's....Just don't know how to do it.

Ed

[ghh3rd]

I just stumbled on this while searching for something else... don't know how I missed it, but it sure is good info!

[richbug]

Keep in mind... Sulfur is flammable, Think road flaresx10.

I added a few ounces to the top of my Lyman Mag 20, and turned it on. when It go to temp, I had a nice puddle of melted S on top. when I stirred it all hell broke loose. White flames 5-6 feet high.

When all was said and done there was a cake of slag on top of the pot. The junk alloy that was in the pot seemed to cast much better.

[Nose Dive]

Wow guys...acid in the pot..whew... Please remeber chemical 'gear'...breathing equipment, saftey glasses...proper gloves at bare minium. Site ventiallation..up wind of the pot... bit of baking soda,,fire exteinquisher.... at least... Certainly no 'small feet' around the work....

I just read BORAX in the pot helps when smelting... never tried it, but am gonna!

"it ain't fun if your hurtin"...

[RP]

Well I got some sulfur today and going to try it out I think I have a batch of ingots that has zinc in it. After reading the post again Iam kind of nervous. If I got it right you fire up the pot when lead gets just before melting point thick stage you add the sulfur. Then you heat it on up and stir with a long stick staying up wind at all cost and be ready for flame on. Let that burn out add sawdust to flux then let sit. The zinc should turn to a hard crust on top. That sound about right ? Also if you do the same thing twice would it remove more I was thinking so. Another note what if you did the sulfur treatment to alloy that did not have zinc in it what do you get?

[RP]

Well I got back to it today melted down the mix again and sulfer treated it again got more crud. Did it again got more crud. So I think with or without zinc your going to get some crud whats getting removed unsure. I dont have any acid to check my ingots that I poured out of the mix. But I was going to cast some boolits with them and see what happens. Has anyone tried the sulfer on a alloy that is know not to have zinc in it.

[kbstenberg]

Good inf.
If I could add 1 more question. What are the symptoms that make you think you have Zink contaminated lead?
Only once have i had a lumpy surface on my casting pot during my heat up process. An that went away when i fluxed and or when the melt got to casting temperatures.
But the problem I'm having is that my 44cal bullets are not expanding when shot into testing media. My alloy is both 50%clipon/50%stickon WW or 75%clipon/25%stickon both have about 1%tin added. The expansion media that I'm shooting into is both 1 gal. jugs and wet newsprint. Everything is shot at 25yards
I'm using both testing medias to see if there is a difference in how the bullets expand.
The bullets I'm using are 503 solids ah the 503 with the small HP pin. The heaviest load has been 18gr 2400, with both the solid an, HP with both alloys penetrating to about 18" of news print without any expansion.
I have only been casting about a year. But it seems like i am getting good fill out on everything I'm casting. I have about 5/ 44cal molds, and 2/30 cal molds. an i don't go above #8 on my lee pro 4/20. But i don't have a thermometer.
If it makes a difference i can adjust my casting temp to go from shinny surfaced bullets to frosty. I tend to stay on the shineyer side
I hope i haven't muddied the water with excessive detail!
Kevin

[sagacious]

Only once have i had a lumpy surface on my casting pot during my heat up process. An that went away when i fluxed and or when the melt got to casting temperatures.
...
But it seems like i am getting good fill out on everything I'm casting.
...
If it makes a difference i can adjust my casting temp to go from shinny surfaced bullets to frosty. I tend to stay on the shineyer side
Kevin
Those two details argue persuasively that there is not likely to be zinc in your alloy. Could be, but as far as I can see, nothing in your description indicate the usual problems from zinc contamination.

I'd recommend you start a new thread for your question about lack of expansion, and the relevant factors can be addressed one at a time, and the fix identified. Good luck.

[kbstenberg]

Thank you Sagacious! I was hopping i hadn't been contaminated. Hopefully i have just water hardened to too high of a BHN for expansion.
Kevin

[sagacious]

Very good-- your question didn't mention quenching, but I thought that might be the problem. Those quenched bullets can be surprisingly hard. Try air-cooling and you'll probably get the kind of results you're after. Good luck!

[45nut]

Mr. 45nut, Sir:
I was reading the thread ( a "sticky") concerning the removal of zinc with sulfur in the lead, and lead alloys section of your cast boolits site.
In reading about some of the more dramatic reactions witnessed by some of your site members, I recalled from my adolescence the fact that sulfur and zinc , when intimately mixed together make an effective, if somewhat dirty , model rocket propellant.

I thought you might want to be aware of this ( you probably should verify this, as it was a long time ago... ) and probably make your membership aware of this as well.
At the concentrations of zinc generally experienced in lead melts, there is probably little or no danger . But if someone were to try to "clean" some granulated zinc with a substantial amount of sulfur , I would not be surprised if the bottom of a cast iron pot melted out from the reaction.

Again, I'm not trying to cause a panic, I just felt that I had some specialized knowledge ; if it turns out that I'm wrong , please accept my apologies in advance.
( love your site, by the way; - will get around to joining one of these days )

regards,

From a innocent bystander ;-)

[sagacious]

I can vouch that the wrong flux can light a pot of zinc on fire-- which is to say, molten metal that is on fire. Imagine that for a moment.

Powdered zinc should not be mixed with powdered sulfur. It will burn with exceeding vigor. Molten lead and sulfur do not pose any explosion hazard that I am aware of, but I still would not mix lead dust with sulfur. Use both common sense and safety gear at all times when working with anything molten or flammable.

[Charlie Sometimes]

The "innocent bystander" is right. I don't know why I never thought of it before! :groner:

I've got a book on model rocketry printed in 1960 (Rocket Manual for Amateurs, by Capt. Bertrand R. Brinley, Project Officer, 1st US Army Amateur Rocket Program) and it lists a mixture of zinc dust and powdered sulphur as a propellant, and several pages of recommendations and formula.
It says that a properly designed amateur rocket could be propelled to heights in excess of 100,000 feet by this mixture. It also states that there are no reliable performance parameters in mixture ratios. Purity of the ingredients, particle size, thoroughness of mixing, amount of air present, etc. effect the performance. It also says that zinc and sulphur burn readily in open air, and can be ignited by squib or random spark. Most any metal when powdered will burn in similar fashion, provided with the correct amount of oxidizer.
Reading more here, it sounds like mixing it is similar to the making of BP, that many other threads here have related the processes.
So, it sounds like you DON'T want to confine it while burning out in the pot, which will keep you from sending any lead pots or ladles into shallow earth orbit, or from knocking the earths axis off center. But, you could generate enough heat to melt your pot down too.
Caveat Emptor (my latin sucks)- Mixer Beware!

[trooperdan]

Charlie, you must have been an experimenter like me! I'd like to buy your book, if you ever decide to sell it!

[Charlie Sometimes]

I've seen several like it over the years- next one I find, I'll get it for you. I'll be on the look out now, and probably never see another! :roll:
The first one of them I ever saw was in my 8th grade science class, and that got me started into experimenting with scientific stuff. It didn't help that the teacher, encouraged me! :grin: He let me have stuff that would get us all sent to jail these days. You can't imagine the things I tried making back then. I would have won the science fair that year, but I had a temperature fluctutation in my "lab" and it ruined the entry experiment. I was growing various types of crystals, and my supersaturated solution dumped too fast due to a temperature drop, and I had nothing to fall back on.
When I found this copy of it, I couldn't refuse it, and have had it all these years.

[Nose Dive]

MMM... The crud your gettin out could be the crud (sulfur) your puttin in... Ummm..Dunno..ain't that bright... But be careful... Puttin stuff in the pot is tricky... Why I only use pine saw dust..

Thought about BORAX..use it ofte in tanning deer hides...but..no..don't know the impact and ain't got the place and time to 'test' it. So..bit of saw dust and maybe some old grease to flux...

Just be careful....

"it ain't fun if your hurtin"

Nose Dive

[CowboyPoetWannabe]

Charlie and trooperdan,

A PDF copy of the book, "Rocket Manual for Amateurs," is available at:
http://www.rocketryplanet.com/content/view/2766/95/

BEWARE...the file size is quite large.

-CPW

[Charlie Sometimes]

That's the book! Mine looks just like that. :smile:

[LeadThrower]

Folks have been talking about the noxious fumes of burning sulfur, but I didn't see anyone identify the product. It's sulfur dioxide, and truly nasty stuff. Take the words of caution seriously -- the suggestions for respirators are good. For details, see the OSHA site: http://www.osha.gov/dts/chemicalsampling/data/CH_268500.html

[hunter64]

No one has mentioned the fact that when Sulfur is burning it stinks to high heaven. First time I did the sulfur treatment for zinc removal years ago I did it in my backyard and the neighbor thought there was a huge Natural Gas leak somewhere. They don't smell at all the same but to the uninformed they smell exactly the same so be careful where the process is done, you might get some unhappy gas company employee's breathing down your throat.

[Fixxah]

Those boolits look sweet. How did you know there was Zinc in the mix? Poor boolit fillout?
My apologies if I missed the explanation, I skipped to reply.

[rogn]

Burning sulphur produces sulphur dioxide, which is used to kill bugs and to sterilize dried fruits. When it combines with wter it forms sulphurOUS acid, which is not as strong as sulphurIC acid. If you get a good blast of the fumes your throat and/or lungs may become very inflamed . Throat could swell shut in minutes and lungs can fill with fluid. So do your processing in a very well ventilated area. The suggestion of a respirator is a very good one.

[xfoxofshogo]

i have tride this and found you lose lead too but if you take the slag and re het it at lead temp after braking it up in a pot you can melt that lead back out and if you think its has to much zinc in it take it to the scrap and sell i melt all my zink down too and take it to the scrap thay pay a nuff for it here to wher my lead ww are all most free not i do not sulfer the zinc i know is all zin for thers nuthing left win your done but you can make some cool look rocks that sparkle lol

[xfoxofshogo]

o scrap the steel too the price is up right now 1000 lb is like 130 buck here

[DrB]

I take it that no one ever followed up with a rotometals assay to characterize the elemental depletion in the alloy from a identified starting point?

Any conclusions on this re the fire and sulphurous acid hazard? Are they reasonable with proper precaution or is this meritless as compared to just diluting the contaminated alloy?

[Gswain]

Ill second that this method works. Had some lead alloy of questionable origin, fizzed when I acid tested. Went to the hardware store and bought some sulfur, it was mixed 50/50 with gypsum. dumped about a cup into the melt, held my breath, stirred like hell, and stepped away for a couple minutes. You do not want to be ANYWHERE NEAR the fumes from that ****. Its miserable. Went back, stirred again, stepped away. After about 5 minutes, no more funky smoke, and clunky chunks I could scoop out. Now alloy doesn't test for acid, so all turned out well!

[Arnie]

Did any one figure out what Zinc does to a lead alloy.I used to use Linotype to cast 500 grain 45 cal bullets and i would buy the lino in type form from a guy .One day he melted all he had together and i bought it in ingot form .When i cast with that new batch of ingots the bullets would come out of the mold with a shrunken spot on one side and would actually bend as they cooled . I was told by a type setter that they use spacers made of zinc between the type letter so that guy melted all those spacers in with the good lino and ruined it . Arnie

[Dthunter]

Anyone have any idea as to how much zinc it takes to cause problems?

If I have 40 pounds of wheel weight lead melted in a pot, and 5-10 zinc wheel weights,or 4-5Zinc Wheel weights, or 1-3 zinc wheel weights? What is enough Zinc to create problems?

thanks guys for your input!
Straight shootin!

[badbob454]

depends on how much zinc is in your good lead .. usually 1-3 wont hurt but i would be comfortable if i missed only 1 ,.... 2-3 i will be stressing out

[thos]

I gave it a try this weekend. I had 100# of very "contaminated" lead. It seems to have worked, but the real problem for this amateur was recognizing when to stop the process.
After repeated fluxing with sulfur, there seemed to be a change in the quality of the slag. It became more a fine powder and the creation of the hard sulfate slowed. I had significantly reduced the weight of the pot and I was thinking that I my be removing tin or antimony or even binding with lead at that point.
I don't know if the change in consistency was the result of the temp of the pot, the reduction of zinc, or some other factor, but I stopped at that point. I have yet to cast boolits from the lead, but in did seem to fill the ingot mold without the anomalies that I was getting. The hardness of the lead was known before, I'll be checking the hardness of the lead after. I'll post the results if anyone is interested.
How did you recognize when to stop? Did you see a change in the properties of the slag?
I would not expect acid to be a good test because there would alway be a trace (1.6%) zinc remaining.
Thanks for a great post.

[nwilson1024]

I (along with others I assume) are interested in the hardness before and after if you get a chance :)

[popper]

Reading on HT hardening of arsenic and sulfur, they seem to have similar capability and sulfur is easier to come by. Anyone have any data on it? Don't want to make PbSo4 or So3. So2 isn't too bad, SO3 is NASTY.

[geargnasher]

Popper, sulfur is a grain refiner like arsenic, and will improve the casting qualities of any lead alloy.

I too am interested to know about the formation of lead/sulfur compounds when doing this. Thos had a good point in post #71 regarding when to stop. I'm under the impression that zinc is far more reactive with the sulfur than lead, tin, or antimony, so it will react first, but at a point when the zinc is mostly gone, will continuing to add sulfur create other compounds? My chemistry knowledge is limited out here.

Gear

[popper]

Sulfur mixed with lead is a grain refiner, mixes with the antimony and if you do it right, is better than arsenic for a HT hardener. I'm thinking it needs to be combined with the fluxing to reduce the creation of SO? products. Under the right conditions, it combines with Pb to get various PbSo? compounds. I don't find anything saying it combines much with Sn. Most of my reading on the subject is related to smelting lead ore. Has some phase diagrams which relate to quenching process(hardness) and the end products after quenching. I'm guessing , but I think the powder after the zinc is removed is PbSo4, hard but granular, not chunky.

[Flintlock Hokie]

The stick ons are most likely pure lead. Squeeze them with a pair of side cutters and you will know right away.

I've found quite a few "stick-ons" that are zinc. I believe all were marked as such with Zn.

[One Gun Andy]

Another great post! I'll be heading to the hardware store for sulfer tomorrow morning!

[RyanJames170]

that is neat

[zxcvbob]

I have about 7 or 8 pounds of zinc-contaminated lead. I can't throw anything away, so it sat there on my casting bench mocking me. A few months ago, I melted it down and cast a bunch of little ingots that weigh about 3 ounces. I've been adding one to a 20# batch of medium-soft lead (range scrap) and stirring it in when I cast wadcutters, and run the furnace hot. I get just a little bit of "oatmeal" floating on top, but I just leave it there. Some of it harmlessly oxidizes away, but most just eventually dissolves after I add a few more ingots of good lead. It casts just fine. I've used up several pounds so far.

"The solution to pollution is dilution!"

[Dumasron]

I can't see any pics. Is there a link?
Does zinc cause a purple, foamy dross on the lead when melted and
a gold color on the ingot?
Thanks
Ron

[Markbo]

I have a pot that is hardened (I ran out of Propane!) that I know is Zinc contaminated. When I remelt, at what temperature should I try this sulphur treatment? At Lead melting temp or zinc melting temp???

[Nose Dive]

Well Markbo... Both. I start at 600 or around 550 and flux saw dust.... then hit it with the sulfur.... Now, Zinc melts in the 700s so, why do I do it now? "Cuz". If the smelt is really contanimated, this is my attempt to capture the already combined zinc bits. Then... heat up to above the zinc melt point and hit it again with saw dust. Then..you guessed it.... the sulfur. I get a good dross with each flux with sulfur and really, do it twice at high temp. Dunno why...just do.... Sometimes I may sulfur flux there or four times. The dross does change over attempts and finally finish with wax. Then I add my tin and mix.... Sometimes...it works really well. Good Luck.

Nose Dive

Cheap, Fast, Good. Kindly pick two.

[Markbo]

I found some sulfur at the local plant supply place pretty cheap and a 5 gallon bucket of sawdust free at Home Depot. Finally got a day off today, but it is unusually for this time of year here, absolutely dead calm. I think I will wait till we get some breeze back and try it then. In the meantime I have lots of buckets to separate. I think in the end the manual separation will be worth it.

[popper]

Try using copper sulfate instead of sulfur to get the zinc out. Doesn't make a fire and does the same thing. Cost is about the same, toughens the CBs. It will also remove tin but not antimony. Check the thread under adding copper.

[Markbo]

Finally had time and perfect weather and the same time. Breezy to waft away the fumes! Got a lot more dross out using sawdust and sulfur. Probably 10-12 ladles full of oatmeal looking stuff out of roughly 40 lbs of lead. Real colorful too. Lots of blues in spots. Must have been the sulfur - never seen it like that before.

Anyway, the test will be in the casting. Now I have to wait for time and weather again. :) I DID take the opportunity though to filter all my wheel weights. From 6 x 5 gallon buckets I got 3 full of lead only and will sell the 3 full of zinc, steel & aluminum. Maybe they'll trade me for some lead. ;)

[Lizard333]

Finally had time and perfect weather and the same time. Breezy to waft away the fumes! Got a lot more dross out using sawdust and sulfur. Probably 10-12 ladles full of oatmeal looking stuff out of roughly 40 lbs of lead. Real colorful too. Lots of blues in spots. Must have been the sulfur - never seen it like that before.

Anyway, the test will be in the casting. Now I have to wait for time and weather again. :) I DID take the opportunity though to filter all my wheel weights. From 6 x 5 gallon buckets I got 3 full of lead only and will sell the 3 full of zinc, steel & aluminum. Maybe they'll trade me for some lead. ;)

Are you sure you found aluminum WW's? I've personally sorted through 30+ buckets of WW's and never once found an aluminum WW. Your not tossing the ones marked AL in the scrap pile? These are lead, just the AL means they are ok to install on aluminum rims.

[Markbo]

I am familiar with all the different wheel weight markings, thanks lizard. I am 100% sure I have found some aluminum weights. Very few, but they are out there!

[Packntchr]

As a chemistry teacher, I want to point out that Hydrochloric Acid (pool supply houses call it muriatic acid) will work as well, and is marginally safer to work with. In either case, beware of the fumes.

[Whizzer]

I am familiar with all the different wheel weight markings, thanks lizard. I am 100% sure I have found some aluminum weights. Very few, but they are out there!

Hard to believe.... Why would anyone make a weight out of something light?

I control my smelting temps, but it slows down the process. But I've only had a few zinc weights ever sneak by my sorting process. They float easily to the top.

[Cesure]

I've been reading this thread with great interest. I don't have any WW, but I might pick some up from a local tire place. I can get a lot of sawdust, but that's mostly chainsaw shavings which I think I might have to dry before using. Wouldn't sawdust alone remove zinc? Would that just be too slow or require too much sawdust? Also, would venison tallow be an acceptable substitute for suet or lard? Would it have to be rendered first to remove the water from it? It would be good to find a use for it.

[badbob454]

Hard to believe.... Why would anyone make a weight out of something light?

I control my smelting temps, but it slows down the process. But I've only had a few zinc weights ever sneak by my sorting process. They float easily to the top.

they do make an aluminum /zinc alloy wheel weight , never saw a pure but who knows maybe in texas they want to make em bigger .., if you cant cut em dont put em in the pot ...

[Relsom]

Good info. I was wondering what to do with some WW ingots i bought that i think are contaminated. I'll give it a try when the weather clears up.

[Markbo]

Relsom, FWIW I used a respirator that I keep for using with a blaster. It did NOT help much! Those sulfur fumes are no joke. I wore my respirator, stayed up wind and held my breath when I had to get close to spoon off the dross. I just used a long 1x2 for stirring so I could stay away from the pot. I must say though that following advice of low temp sawdust, then sulfur, then repeat at higher temp got a lot more dross out of the pot than I thought was still in there!

[grumman581]

Relsom, FWIW I used a respirator that I keep for using with a blaster. It did NOT help much! Those sulfur fumes are no joke. I wore my respirator, stayed up wind and held my breath when I had to get close to spoon off the dross. I just used a long 1x2 for stirring so I could stay away from the pot. I must say though that following advice of low temp sawdust, then sulfur, then repeat at higher temp got a lot more dross out of the pot than I thought was still in there!

You need to use a positive airflow respirator / hood. They are relatively easy to make and you can use a garden hose for the forced air supply so that it can be coming from an area well away from the toxic environment where you are working. The air supply can be just part of a shop vac if you hook the hose to the exhaust port on it. The first one I made MANY years ago was made from a paper grocery sack with a view port cut out and a clear panel taped inside of it for a view port. I had seen plans for this on the web and decided that it was simple enough that I would give it a try. I was working with some chemicals that produced some rather hazardous fumes and I was in a relatively enclosed space. Even with just the paper hood, I could not smell the chemicals.

Since then, I have adapted an Israeli surplus gas mask to do the same thing. Here's a link to a Finish one for $20 that would also work:

http://www.sportsmansguide.com/net/cb/new-finnish-military-surplus-gas-mask-with-bag.aspx?a=641202

To convert it to a forced air supply, you need to modify the screw-on gas cartridge to have a connector for whatever air supply you are using. Another advantage of this is that you can have your air source inside the air-conditioned part of your house and you'll have cooler air that you are breathing in.

If you don't have a shop vac or if you want something that is not quite so powerful, the 120VAC air mattress type inflators also will work and will produce plenty of air supply for your breathing needs.

When using the modified gas mask, I leave the facepiece slightly looser so that the air doesn't all have to exit through the designated air port. It's more comfortable that way anyway.

[hickfu]

I picked up some Sulfur today to try to get zinc out of alloy I purchased, Thanks to everyone on this thread. I thought I was going to have to throw the alloy away or mix it 25% to 75% new alloy. At 800lbs of possible contaminated alloy, I dont have the money to buy 2400lbs of good alloy.


Doc

[Markbo]

Grumman, I was thinking about that gas mask you linked to. I get enough funny looks from neighbors already. I can just imagine what the gossip would be if they saw me walking around wearing one of those with a long hose attached to it! :mrgreen:

[grumman581]

Grumman, I was thinking about that gas mask you linked to. I get enough funny looks from neighbors already. I can just imagine what the gossip would be if they saw me walking around wearing one of those with a long hose attached to it! :mrgreen:

Just make sure that you wear the proper protective clothing also...

http://www.latexbay.com/ebay/germany/god-102115.jpg

Uhhh... Maybe not...

[Sasquatch-1]

Just make sure that you wear the proper protective clothing also...

http://www.latexbay.com/ebay/germany/god-102115.jpg

Uhhh... Maybe not...

Now that one would have been worthy of one of the photo threads.

[tallow98]

What is the bes way to detect zinc before messing up?

tallow98

[Markbo]

In my case it was wheel weights. There are already some advice listed about not letting get in there in the first place, which is sure a lot easier than getting it out once it is already contaminated. :mrgreen:

[mold maker]

Zinc is a relatively new problem(5-6 years) and there is no absolutely fool proof method of keeping it out. That is however, the best approach.
As to getting it out after contamination occurs, I think the jury is still out. I've read, and reread what has been discussed here. It seems as if several have tried with different degrees of success. Those with chemical backgrounds say it will work. Skeptics like me are waiting for the unfortunate event to need it.
Probably, I'd take mine to the scrap yard, with it marked as such.

[popper]

Copper sulfate works much better, doesn't have the terrible fumes. It adds Cu which goes into the lead just like sulfur. Cost is the same. Add just a little at a time (tea spoon in a 40# pot) When it turns white, mix it in, add more. You're done when white crystals stay on top. After all the zinc is removed, let it cook for 1/2 hr, add uncontaminated lead to get the % Cu you want. It will remove tin, not antimony. 4 pennies into 10# pure will give you about 2 cups of fine brown powder. You should wear a dust mask when doing this, no respirator needed and it doesn't flame up.

[tallow98]

Ok. I read in Lees reloading handbook that zinc wheel weights are shiny. Is that the only way to check for zinc?

Tallow98

[grumman581]

Ok. I read in Lees reloading handbook that zinc wheel weights are shiny. Is that the only way to check for zinc?


Don't melt at too high of a temperature and you can skim the zinc wheelweights off the top.

They will also usually have a "Zn" on them.
They are noticeably harder when you take a pair of side cutter pliers to them.

[Lizard333]

MOST of the time the zinc ones will have Zn on them. Sort through a couple of buckets and you will get the feel for it. I keep a magnet and a pair of side cutters with me when I sort. If it isn't magnetic (on the ends), and I can cut them with side cutters, they are lead.

Keep your melt below 700 and the zinc ones will float.

After a couple of buckets you will developer a feel for the WW's. the Zn ones won't "feel" right. Not being as dense, they don't weigh enough for their size.

[Markbo]

When you drop a lead wheel weight on concrete, there is a dull thud. They also have a particular shape that you will begin to recognize. When you drop a zinc or steel weight onto concrete, there is a definite 'ting' sound. Drop is on the weight, not on the clip. If you are not sure, throw it out. A tossed lead weight here and there will not be missed. From experience it is a heckuva lot easier to separate ahead of time and melt at lower temp rather than (as I did) melt everything and get the zinc out. I just had no idea what a pain it would be or I would have been more careful to start with. Now I sort all my weight when I get them. I don't even take any zinc or steel weights home.

[funshooter]

Do you think that putting a contaminated load of lead in a melting pot and putting that into a kiln that you can control the heat on.

Bring the temp up to about 800+ deg. and slow cool the mix over a day to just over the zinc melt temp. but under the lead melt temp.

That you could pour off the zinc and have a good lead mix left over. There would be little work to do it. just time.

I melted about 47 Lbs. of wheel weights and I did not read this post before I did it and I am wondering if I now have contaminated ingots.

I did just that to soften a steel punch from an ironworker so that I could drill and tap it. and I slow cooled the thing for 3 days bringing it down 100 deg. every two hours and the carbon migrated out to the surface and was about 1/16" thick. I chipped it off , drilled and tapped my hole.

Any advice

[Sasquatch-1]

From what has been posted in the past, try filing some of the suspect lead and applying a little Muriatic Acid to the filings and see if it foams. This is supposed to be a sign of zinc contamination.

[Cesure]

Bring the temp up to about 800+ deg. and slow cool the mix over a day to just over the zinc melt temp. but under the lead melt temp.

I think you might have that backwards. Zinc has a higher melting point than lead. So after slow cooling down below 780degf, you would have solid zinc floating on top of molten lead. But you would still have some zinc in the molten lead until you chemically removed it. Better to slowly raise the temp to 700degf and skim the zinc off before it melts. But you'll still have some zinc in the lead.

[funshooter]

Thanks guys

still learning every day

[bangerjim]

Just tried some KNOWN PURE 100% lead in the pot with sulfur added (1/2 tsp/5#) and got black crud from PURE lead. Not sure what it is combining with, but is definitely not zinc! And it is really black and heavy for a flux "floater".

Smell reminds me of hell.....4th of July and making fireworks.....Yellowstone mud pots....all those good "sulfury" things.

As far as testing COWW......use the old "bell ringer" method. I keep a large 1" steel rod about 8" long on the bench when sorting. Banging zinc on it sounds almost musical! It rings. Lead will sound totally dead. That is the best way I have found to tell them apart....other than just reading the label on the side that says ZN!!!!!!!! I even find SOWW's that are Fe....steel/iron! Beware if you are paying good $$ for Pb and there are a bunch of Fe ones in there.

Happy meltin! :lol:

[3jimbo3]

I just smelted a 5 gallon bucket of ww and it yeilded me 99 ingots. Some of my ingots came out nice and shinny and sone came out kind of frosty colored. I was not sure about the zinc so just to make sure, the ingots went back in, melted down, and I fluxed with copper sulfate. I fluxed 3 to 4 times scrapping the pot real good and stiring with a wooden stick (pine). I then poured my ingots and I still got some frosty looking ingots. At leat I know they are clean anyway. Does anyone know why some are frosty looking and others are shinny, out of the same mix?

[Lizard333]

I'm guessing the frosty ones came after you poured a few rounds of ingots through your molds. Same reason you get frosty boolits in a hot mold. Your mold was hot. Don't worry about it.

Btw, its a LOT easier to check for zinc with a small bit if muratic acid. If it bubbles when applied, you got zinc.

[3jimbo3]

Hey thanks for that insight. I will pick some up and try it. That mighr just save me a lot of work.

[kaptain kartridge]

Muriatic Acid (Hydrochloric acid) will digest all of the alloy, Lead, Tin, Antimony, and Zinc. Once in solution, the solution can be chilled, and the Lead Chloride will solidify and settle out. So, a carefully weighed sample, dissolved, and the Lead Chloride strained out and weighed, will give you the amount of lead in the alloy. I believe that the other metals can all be precipitated out of solution, to give the ratios of all the metals in the alloy. But, it has been a long time since Quantitive Analytic Chemistry class, to remember the whole process. Any chemists out there?

[badgeredd]

Can you believe it? I went looking for some gardening sulphur at our local Wally World, Menard's, Home Depot and our area chain Meijer's and not one container of sulphur to be found! I wanted to compare results using sulphur to results using copper sulfate for my own knowledge. I have to try few more places to try a bit out of the immediate area yet for the sulphur.

Edd

[Markbo]

I went to a nursery that sells more stuff than the box stores to find it.

[JLMEMT]

I guess I will weigh in with my experience here.

First off someone asked if you should just use the sulphur method to avoid sorting the zinc weights out? NO!!!!

I was not really aware of zinc or the problem it is when I tried my first WW smelt recently. I had only done a little lino before. I came in and started doing some reading and found out about zinc. I am almost positive I had a bunch of zinc towards the end. I thought they were different, but tried the let's see if it melts route. With the pot good and hot they slowly melted. I tried to chalk it up to the paint or coating but it didn't look the same.

So I read up here and decided that I had some sulphur and would give it a try. Molten sulphur is nasty stuff so the first time I just kind off dumped it on and stepped back. You get the black crud talked about above but I realized that I was not removing much if any zinc. Next I tried to stir just a little quickly, essentially the same. You have to mix it into the melt pretty well. Be aware that once it reaches the right temperature it starts jetting gases that ignite with very hot flames. Now it is doing what you want. One of the first times I did this correctly I got a hard thick layer on top of a straight sided pot. It is very hard to remove at that point and I ended up breaking through and splashing lead everywhere. Best if you have a pot that is slanted out for this so you could remove the cake intact. If not you want to break up this cake while it is cooking and before it solidifies. This is a distant second, but the best I figured out for how I was doing it. Breaking it up you are bound to get some lead on it that you will lose in the process. If you have some patience it is better to do several small amounts of sulphur to keep the layer thinner, in my opinion. I tend not to be so patient with such things.
One thing I did not figure out is how much zinc is being removed, when is a good time to stop, etc. I did several rounds in each pot and finally called it good and tried some casting. They cast as well, if not better than early in the process before I believe I contaminated my lead.

I agree with Markbo. I also found some at a nursery years ago. If you cannot find that option you can find it in a more expensive form at Fireworks supply companies such as Americanpyrosupply or Skylighter. I have both.

[JLMEMT]

I guess I will weigh in with my experience here.

First off someone asked if you should just use the sulphur method to avoid sorting the zinc weights out? NO!!!!

I was not really aware of zinc or the problem it is when I tried my first WW smelt recently. I had only done a little lino before. I came in and started doing some reading and found out about zinc. I am almost positive I had a bunch of zinc towards the end. I thought they were different, but tried the let's see if it melts route. With the pot good and hot they slowly melted. I tried to chalk it up to the paint or coating but it didn't look the same.

So I read up here and decided that I had some sulphur and would give it a try. Molten sulphur is nasty stuff so the first time I just kind off dumped it on and stepped back. You get the black crud talked about above but I realized that I was not removing much if any zinc. Next I tried to stir just a little quickly, essentially the same. You have to mix it into the melt pretty well. Be aware that once it reaches the right temperature it starts jetting gases that ignite with very hot flames. Now it is doing what you want. One of the first times I did this correctly I got a hard thick layer on top of a straight sided pot. It is very hard to remove at that point and I ended up breaking through and splashing lead everywhere. Best if you have a pot that is slanted out for this so you could remove the cake intact. If not you want to break up this cake while it is cooking and before it solidifies. This is a distant second, but the best I figured out for how I was doing it. Breaking it up you are bound to get some lead on it that you will lose in the process. If you have some patience it is better to do several small amounts of sulphur to keep the layer thinner, in my opinion. I tend not to be so patient with such things.
One thing I did not figure out is how much zinc is being removed, when is a good time to stop, etc. I did several rounds in each pot and finally called it good and tried some casting. They cast as well, if not better than early in the process before I believe I contaminated my lead.

I agree with Markbo. I also found some at a nursery years ago. If you cannot find that option you can find it in a more expensive form at Fireworks supply companies such as Americanpyrosupply or Skylighter. I have both.

[1bilmr59]

Very Good post

[ProfGAB101]

Just tried some KNOWN PURE 100% lead in the pot with sulfur added (1/2 tsp/5#) and got black crud from PURE lead. Not sure what it is combining with, but is definitely not zinc! And it is really black and heavy for a flux "floater".

Smell reminds me of hell.....4th of July and making fireworks.....Yellowstone mud pots....all those good "sulfury" things.

As far as testing COWW......use the old "bell ringer" method. I keep a large 1" steel rod about 8" long on the bench when sorting. Banging zinc on it sounds almost musical! It rings. Lead will sound totally dead. That is the best way I have found to tell them apart....other than just reading the label on the side that says ZN!!!!!!!! I even find SOWW's that are Fe....steel/iron! Beware if you are paying good $$ for Pb and there are a bunch of Fe ones in there.

Happy meltin! :lol:

You have made a form of lead sulfide - basically the same as the crud that is left in a automobile type lead acid battery after its well past its usable life.

[Steven Dzupin]

Please take the time to read Lyman's book on bullet casting.

A wealth of information .

Pictures of the result of Zinc contamination as well.

Regards,

Steve

[DeputyDog25]

Copper sulfate works much better, doesn't have the terrible fumes. It adds Cu which goes into the lead just like sulfur. Cost is the same. Add just a little at a time (tea spoon in a 40# pot) When it turns white, mix it in, add more. You're done when white crystals stay on top. After all the zinc is removed, let it cook for 1/2 hr, add uncontaminated lead to get the % Cu you want. It will remove tin, not antimony. 4 pennies into 10# pure will give you about 2 cups of fine brown powder. You should wear a dust mask when doing this, no respirator needed and it doesn't flame up.


Popper, where can you get the Copper Sulfate, I think I am going that direction rather than the fumes, flames, and whatever else sulfur might do.

[Markbo]

Good questions. And pennies are about 98% zinc & 2% copper. Seems you'd be spinning your wheels using oennies.

[AllanD]

A physics teacher I spoke with about this said sulphuric acid( Battery acid) would work to identify zinc wheelweights. The zinc would react the lead would not.


Hydrochloric Acid would react more tellingly with Metallic Zinc...

To get Copper Sulfate go to the plumbing department of you "Big Box store"
(Lowes or Home Depot) and look for something called "Root Kill"

(Read the ingredients)

Do not add the blue crystals directly to hot metal, blue crystal Copper Sulfate is in the Pentahydrate form
(Look up "water of crystallization") and if heated suddenly this water comes out, often violently...

[AllanD]

Borax should be "Safe" to add to molten metal as simple Borax is the basic flux for brazing or gas welding

[garrisonjoe]

I've found laundry "borax" is a safe flux agent, but be aware it has water bound up in the mineral, too. Let it puff up on the surface - it puffs to about 4x bigger volume and is very fluffy. After puffing up, it readily grabs dirt from the alloy and carries it to the surface. I've not seen it affect any of the alloyed metal content. It "dries" the wall of the pot very quickly, so usually some wax or 2 cycle oil is needed to keep the pot walls wet enough to keep alloy from sticking to the walls. Takes a VERY hot lead pot to make this form of borax go molten like brazing flux does, however.

Borax will NOT pull zinc out of the alloy (which I thought was the topic of this post)!

[garrisonjoe]

FWIW I used a respirator that I keep for using with a blaster. It did NOT help much! Those sulfur fumes are no joke. I wore my respirator, stayed up wind and held my breath when I had to get close to spoon off the dross.

Sulfur dioxide gas is NOT removed by a standard dust/silica respirator like would be used for sand blasting (or sanding). You need a specialized acid fume cartridge which neutralizes the SO2. After my 5 years experience of running a large Arizona copper smelter back in the 70s, sulfur fumes are nothing to be cavalier about - this stuff can cause serious respiratory burns, and can asphyxiate you in high concentrations. Please be real careful with this, and be aware the SO2 smell will attract attention at very low concentrations. SO2 is pretty hard to oxidize to the next state (sulfur trioxide, SO3) - but if it does, it is certainly toxic and a lung and eye destroyer, as it rapidly combines with body moisture to make strong sulfuric acid.

[Nose Dive]

Gents... Believe garrisonjoe is correct. "any old" respirator will not provide the level of safety needed for gaseous fumes. You will need a properly selected 'acid gas' cartridge for the protection needed. Or, 'get the right cartridge for the gas' you may be exposed to. Dust masks are for dust....not gases. And, here too, you need the 'right dust mask for the dust' to which you maybe exposed.

And, here too, cartridge masks do NOTHING for oxygen deprivation.

What you don't know can hurt you.

Nose Dive

Cheap, Fast, Good. Kindly pick two.

[Nose Dive]

Gents... Believe garrisonjoe is correct. "any old" respirator will not provide the level of safety needed for gaseous fumes. You will need a properly selected 'acid gas' cartridge for the protection needed. Or, 'get the right cartridge for the gas' you may be exposed to. Dust masks are for dust....not gases. And, here too, you need the 'right dust mask for the dust' to which you maybe exposed.

And, here too, cartridge masks do NOTHING for oxygen deprivation.

What you don't know can hurt you.

Nose Dive

Cheap, Fast, Good. Kindly pick two.

PS:... be very careful about what you put in your smelt pot. Some of the chemical solutions offered on these pages become very dangerous when we bring up the temp. Protective clothing, properly selected breathing protection, eye protection are in many cases, well, MANDATORY to prevent blindness, burns, and lung damage. ND

PSS: ...be ware, the person you hurt, may not be you.

[Traffer]

I tried using sulfur to get zinc out of lead. It was the most futile thing I have ever done. The lead bubbled with awful bubbles. Then it turned into something like metallic tar or metallic bubble gum. Then it turned onto black powder. The most disgusting stuff.... If it works for you good but for me it is NOT the thing to do. I read up on sulfur in lead and it seems that the big smelters have a heck of a time getting it out. They have to roast the lead to get the sulfur out. A process that is not done at home by any means.

[Arisaka Hunter]

THis is a very infromative post. Thanks all.

[dimaprok]

Copper sulfate works much better, doesn't have the terrible fumes. It adds Cu which goes into the lead just like sulfur. Cost is the same. Add just a little at a time (tea spoon in a 40# pot) When it turns white, mix it in, add more. You're done when white crystals stay on top. After all the zinc is removed, let it cook for 1/2 hr, add uncontaminated lead to get the % Cu you want. It will remove tin, not antimony. 4 pennies into 10# pure will give you about 2 cups of fine brown powder. You should wear a dust mask when doing this, no respirator needed and it doesn't flame up.

Can you please explain a little bit more. I am lost, you go from adding Copper Sulfate crystals to "after zinc is removed" Does that mean once the crystals are mixed in you have to skim the dross which will contain Zinc? Also you completely lost me where you say to add pure lead to get desired percentage of copper? What does that mean? Do the crystals add copper to the lead mix? You also talk about 4 pennies per 10# pot.... Are you saying I need to add 4 pennies to the pot? Why? What kind of pennies? Copper or Zinc? Because all modern pennies are Zinc, so I assume you mean copper pennies? Ok, so we are adding Copper to the mix and that's somehow suppose to remove Zinc? Please explain thoroughly.

[MyFlatline]

Can you please explain a little bit more. I am lost, you go from adding Copper Sulfate crystals to "after zinc is removed" Does that mean once the crystals are mixed in you have to skim the dross which will contain Zinc? Also you completely lost me where you say to add pure lead to get desired percentage of copper? What does that mean? Do the crystals add copper to the lead mix? You also talk about 4 pennies per 10# pot.... Are you saying I need to add 4 pennies to the pot? Why? What kind of pennies? Copper or Zinc? Because all modern pennies are Zinc, so I assume you mean copper pennies? Ok, so we are adding Copper to the mix and that's somehow suppose to remove Zinc? Please explain thoroughly.

Do a quick search on adding copper to your mix, popper has done quite a bit of testing and goes into much more detail there. Yes getting copper in the mix is one of the goals, the other is to get the zinc out.

[popper]

Sulfur in you alloy is GOOD, hardens the alloy. As a process, it STINKS. and will continue to stink if you recycle those culls. Some Zinc is good, hardens the alloy too.

[AllanD]

I use Muriatic Acid to clean my big cast iron smelting pot each and every time.
It will clean cast Iron down to bare metal but be cautious with the virulent yellow solution
(Iron III Chloride) that often results it will vigorously attack Copper, Nickel & Zinc.

Iron Chloride is used commercially to etch excess copper off of printed circuit boards.


BE CAREFUL Muriatic acid (aka Hydrochloric Acid or HCL) reacts VIOLENTLY with metallic Zinc as well as many zinc compounds.

the only substance I personally know of that is more aggressive against rust on Iron or steel is Hydrogen Floride/HydroFloric Acid,
but it is very dangerous in other ways as well.

AD

[Traffer]

I don't know much about chemistry but I know that hydrofloric acid will dissolve GLASS. Yeah, I would say be careful indeed.

[fishingsetx]

Sulfur dioxide gas is NOT removed by a standard dust/silica respirator like would be used for sand blasting (or sanding). You need a specialized acid fume cartridge which neutralizes the SO2. After my 5 years experience of running a large Arizona copper smelter back in the 70s, sulfur fumes are nothing to be cavalier about - this stuff can cause serious respiratory burns, and can asphyxiate you in high concentrations. Please be real careful with this, and be aware the SO2 smell will attract attention at very low concentrations. SO2 is pretty hard to oxidize to the next state (sulfur trioxide, SO3) - but if it does, it is certainly toxic and a lung and eye destroyer, as it rapidly combines with body moisture to make strong sulfuric acid.

I work at a sulfuric acid plant and we burn sulfur to make acid. Ive had to put out several fires in our sulfur storage areas. SO2 is no joke! Just last week, a guy at a copper smelter lost his life due to SO2 exposure.

It can be detected by smell at .01 ppm, a half mask acid gas resperator should be worn at 2 ppm, a full face at 10 ppm and 100 ppm is NIOSH's IDLH (immediatly dangerous to life and health) level. It wouldnt be hard to hit these limits if you didnt have good ventilation.

It is HIGHLY unlikely that any will be converted into SO3 and if any significant amount was, you would know it by smell. SO2 is a burning sensation, almost like pepper spray. SO3 is more of a sharp, stinging sensation.

The only good thing about SO2 exposure, compared to most chemicals, is that there arent many cronic effects from occasional exposure over long periods.

VERY good ventilation and a good acid gas resperator that fits you correctly would be my recommendation if you plan to use sulfur to remove zinc!

Guns have only two enemies: rust and politicians!

[AllanD]

Muriatic Acid does not react with lead at all, but Reacts violently with elemental Zinc to nearly explosively form Zinc chloride, I say "Explosively" because this reaction liberates much HOT Hydrogen.

so Muriatic Acid can be used to identify Zinc



Muriatic acid will not produce the same reaction.
Drain cleaner, Rooto, is the best pure sulphuric acid found in hardware stores. Battery acid is diluted.
You should be able to digest the zinc with the Rooto. The remaining "sponge" will be a more pure lead.
I am not sure, but other elements will also digest out of the alloy as well.
Heat, by specific gravity, will seperate but not completely remove the zinc. Acids will remove the elements. If any other elements are digested by the acids there are other methods that drop out individual elements.
With silver, Karo corn syrup drops out pure silver after processing. Go figuire.

[popper]

From my testing, <2% Zn doesn't hurt at all, actually helps. No problem casting and rifle boolits shoot pretty accurate too. I.E. can't tell any accuracy difference.

[shootinfox2]

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)

[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.

[super6]

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

[Traffer]

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?

[WRideout]

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.
Wayne

[Traffer]

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.

[RogerDat]

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.
.

[Traffer]

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?

[RogerDat]

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.

[super6]

https://en.wikipedia.org/wiki/Lead_smelting#Secondary_lead_processing. Seems you need 1000+ and some other chems. I know my sulfur rescue was At least 1000 degrees.

[Traffer]

https://en.wikipedia.org/wiki/Lead_smelting#Secondary_lead_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.

[Bama]

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

[RogerDat]

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....

[popper]

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.

[pakmc]

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.

[dondiego]

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.

[pakmc]

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

[Traffer]

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.

[slohunter]

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.

[Conditor22]

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

[TwinTurbo34]

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

But does it get rid of the zinc as good as sulfur?

[poppy42]

Copper sulfate has sulfur in it. So the short answer to your question is yes. Just depends on how much zinc you’re trying to remove.

[Krh1326]

I just realized that the copper sulfate that I ordered, and should be here, tomorrow…. Is in crystal form. I read in one of these threads that crystals contain water, and can’t be directly added to the pot? How are they added? The description is fine crystals, but further down, it reads powder. The product pic shows really small blue crystals.
Please forgive my confusion…

[Budzilla 19]

Krh1326, I use the blue crystals also. Just spread the crystals across the hot melt, it should dry quickly! Then just stir it in, it’ll do what it does! DO NOT breathe the fumes. Once is all it’s going to convince you not to do it again! Be safe,

[deces]

Wow, this really is a great thread!

[Waydeo]

I used copper sulfate, zep root killer, to skim off zinc that I missed . Lost about 8-12 lbs. Out of a 50 lb block. My next casting session I'm going to empty my pot and try what I melted today. Fingers crossed.lol

[justindad]

Zep Root Kill works for me. I melted a piece of zinc into lead as a test - turned into a slushy mess. Added copper sulfate a few times, and now the lead is great for casting. I think you can overdo the copper sulfate, and just create more & more slag after all the zinc is gone.

[JimB..]

Zep Root Kill works for me. I melted a piece of zinc into lead as a test - turned into a slushy mess. Added copper sulfate a few times, and now the lead is great for casting. I think you can overdo the copper sulfate, and just create more & more slag after all the zinc is gone.
Curious how much zinc you added and how much sludge you removed.

[justindad]

I added 200 grains of zinc to 4 lb of lead, giving 0.7% zinc. I didn’t consider how much lead I lost, but after going through the process I’m sure it’s a measurable quantity. I just wanted to see if it really worked. The lead did go from trash to useable alloy.
*
It’s so much effort that I’ll only do this for special cases.

[gunshooter]

I just posted to this thread so I can find it again.

[dr_rick]

I did not find any reaction with the sulfuric acid and wheel weights. I did however find a reaction using muriatic acid and wheel weights. A couple of drops on a suspect bare piece of suspect lead will bubble up indicating the presence of zinc or not. I use it on lead that I cannot readily identify. Sulfuric acid works great for "etching".