I may have Zinc contaminated lead

[ghh3rd]

I really appreciate all of the information that I have received from this forum. Every time I skim through a few posts I learn something new, but also wind up with a new question. I was just reading the sticky on "Classics and Stickies" regarding Zinc Wheelweights http://castboolits.gunloads.com/showthread.php?t=40765

I havn't cast bullets yet, but have received my mold and have a pot, laddle and stove. I am all ready to attempt my first cast this weekend (tomorrow or Sunday) after I clean the mold (got my Brake Cleaner tonight). My lead source is a hodge podge of lead from different sources that I had left over from my sinker casting days. Most of it is in ingots that I created from combining lead from various sources, including wheel weights.

After reading about the zinc wheel weights, and how to detect and avoid them, I'm wondering whether I may have mixed some into my lead, since I wasn't aware of them back then. The thread indicates that once zinc is introduced, the batch is contaminated and unusable.

What ill effects will zinc contaminated lead cause? When you purchase ingots that others have created from wheel weights, how can you be sure that theirs is zinc free?

I wonder if I should attempt to use the lead that I have. Fortunately I have one 33 lb chunk that I found on the road about 30 years ago.

Thanks,

Randy

[docone31]

The BP folks are real picky about zinc. They have to be. The nature of BP bumps up the casting.
I have zinc in my melt. I knew nothing about it and forged ahead melting everything I had. Yeah, some weights took forever to melt. I had to push them into the melt and hold them in there.
If it turns out to be an issue, melt it and make ingots. Take the ingots and make a melt. Crank up the heat and get it all melted. Then turn down the heat slowly. Zinc has a signature in a melt. As the heat congeals the zinc, it looks like oatmeal on top of the melt. Skim it off.
There won't be that much in each batch. Heck, once I went to shipyards and got all the anodes and melted them and mixed it with my lead.
Personally, I do not notice the zinc in my castings. I paper patch my rifles and both my .357s, and 45ACPs behave real well with the blended mix.
I read about the zinc, and reingoted my batch. A rather decent undertaking. I then got some roofing lead from a contractor I know. Each day at my shop, he drops off old vent pipes.
I have a 20lb Lee Bottom Pour pot. I fill half way with the blended batch, and put two vent pipes in the melt, stir, skim, and pour. I have to date, gotten great results for my needs.
Old wheel weights, and newer wheel weights have different composition. I constantly re ingot my batches to blend them out.
My suggestion,
Cast a few, fire them off and look-see. That way you will know if the zinc is an issue in your application.
I have found, the harder my castings in paper patching, the better the groups. My .30cals, and .303 cals. love them. I get better groups with them than with commercial jacketeds. Less recoil, better groups. I am pleased with it.
I figuire, if it ain't broke, don fix it.
Start small, and just plain try it out. You won't damage the mold, and with the pot cranked up, the zinc will flow.
If it gives issue, then take steps. Otherwise, relax, keep it small to start.

[Le Loup Solitaire]

Hi, It is difficult to project what actual percentage of zinc must be present to cause any obvious/visible defects in the castings. But when enough is present, you can see it right away; usually a spot that continually refuses to fill out, rounded rings and frosty sunken spots, etc. And you can spend a whole afternoon making crappy bullets, lots of sprues and doing a lot of cussing. Many casters get POed enough to just chuck the entire lot of metal. It takes a lot of patience to try and salvage the metal, but it can be done(eventually). Constant running the pot at a higher temperature along with continuous fluxing and skimming of the dross will get a lot of the contaminant/zinc out of the melt, but it takes a while. Another strategy used along with the first one is to add known "clean" metal with the object of diluting the amount of zinc and reducing the percentage enough so as to not interfere with the surface tension of the alloy. It is not an easy process and is as boring as hell. A third approach used by some is to let the metal just sit quietly after fluxing and just keep skimming the dross from time to time. I have used a combination of all of the above to eventually get zinkoed metal to start to work ok, instead of simply tossing it, but its the "pits"; certainly enough of an ordeal to avoid to start with. LLS

[10-x]

Ever hear of adding unscented Talcum powder to the pot, then mixing? Zinc is supose to "float"?

Not to stir a hornets nest, I've never tried it, just asking........:?:

I carefully sort all my lead, stick on's for BP, WW for general casting and zinc........in the junk box.:lovebooli

[Bret4207]

I'm pretty sure I have a small amount of zinc in my alloy. Every time I cast, and I tend to cast hot, I end up skimming a little of that "oatmeal" dross Docone31 mentioned. I think the key here is it takes a "substantial" amount of zinc to really corrupt your alloy. Now, what "substantial" means and what percentage of the alloy it is depends on a hundred things I suppose. All I know is a couple zinc weights in a 30 lb batch mean virtually nothing, a couple lbs of them...that's different.

I'd follow Docone31's suggestion. I said earlier I tend to cast hot and that helps too. By that I mean get the mould nice and hot, not the melt actually. Your melt can run at , say 700 F, but the mould might only be 550 or 600 and cooling every time you chuck the boolits and stand there looking at them. Fill and dump, fill and dump... If you're going so slow your not having problems with the sprue not cooling fast enough and aren't starting to see frosty boolits then I think you need to go faster or turn up the heat. Do a search on "BruceB speed casting" and read the sticky. That method makes the best boolits I ever saw and takes care of a lot of problems.

[45r]

I melt my WW's in a 7 inch pan and add a handfull after the previous ones have melted.If any zinc ww's are there they will float and I scoop them out before they can contaminate the alloy.When my pan gets 2 or 3 inchs deep and fluxed I pour the allow into my Rcbs ingot mold.I flux with marvelux and sawdust after each handfull.It is time consuming but I end up with very clean alloy.When I put my ingots in my Rcbs pro-melter I only need a little printers flux at the begining and stir with a wooden stick and scrape the side of the pot with a silver spoon and remove dross on top once about every 30 minutes and my boolits come out like they are crome plated and fill out very well.I put in 1/2 pound tin to every 20 pounds WW.If everything is done just right you will only be removing a small amount of ash when you remove the impurities.I keep my alloy temp around 700 to 750 degrees depending on weather and what the mold likes.I like to press the dross to the side of the pot with a wooden stick to make a pinch of ash and scoop it out with my silver spoon.You don't want to remove any antimony,just the ash.

[mooman76]

I am just going with waht I have read but zink causes pore fillout of bullets and it only takes one part per 10,000. Try your lead and see how it works. Keep it isolated as to not contaminate other lead but...... were are learning alot now adays about lead bullets and it would seam size matters more than hardness of lead to prevent leading but if you talk to anyone ouside this forum the first thing they think causes leading is "bullets too soft".
Now going buy what I have read here i tend to think that since zink melts at a higher temp and floats like oatmeal the probuble reason for pore fill out would be not hot enough melt. Try it and see how it works and if it don't do what the others here have posted. No use worrying about it until it is a fact.

[yodar]

Zinc melting point is 787.15°F

I keep my pot below 700 which is easy cause wheel weight/tin alloy I use needs less than lead's 628 df to melt (tin and antimony lowers lead's melting point)

Below 700 dF any zinc will precipitate UP and can be skimmed off.

The same process at 700 d F allows removal of copper from Babbit metals you might have added to punch up the tin/antimony concentration

yodar

[GP100man]

melt & flux your alloy , if good fill out is a problem after mould warm up let the melt sit at `bout 625f to 650f if an oatmeal lookin stuff starts to form in 15 min , you`ve been zinced!!


if you`re patient you can remove a portion of it but will never remove all of it.
i have saved a melt this way , i used the boolits for plinking & informal shooting


GP100man:cbpour:

[Down South]

I cleaned several buckets and partial buckets of WW over the past few afternoons. I wound up with about 640 lbs of clean alloy. I say clean, but one batch got contaminated with zinc. This is the first time that I’ve had such a problem and I think that I know exactly what happened. I usually bring my melt temp up just high enough to melt the regular clip on WW then scoop the clips, steel ww and zinc ww off the top. At this point the temp is not high enough to melt the zinc weights. This batch, after I scooped the clips I added more ww by hand and evidently one or two of the weights that I added were zinc and my melt temp was up high enough to melt the zinc. I got the famous oatmeal in the melt problem. I skimmed as much as I could off and poured my ingots.
Since my casting pot was almost completely empty I decided to try casting with the contaminated alloy. I definitely had problems. I was having problems with boolit fill out and frosting in different areas on the boolits. I found that if I held my temp right at 750 deg and didn’t let my mould get too hot that I could make decent boolits. Later on I’m going to throw all of the contaminated ingots back in the smelting pot to see if I can clean more of the zinc out. I may be able to add some known good alloy to cut the zinc with too. I may try a couple of the zinc contaminated ingots with a couple good ingots and see what happens. Hopefully I can clean the zinc contaminated ingots up enough for use since I have 64 of them. If not then I’ll reserve the zinc ingots for plinking loads since with effort I can get decent boolits with it.