Zinc Removal with Sulfur Report

[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!

[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