How do I knnow if I have zinc contamination?

[Lead Freak]

When casting with a WW alloy I normally end up with a BHN of somewhere around 10.4 using my Lee hardness tester and letting the boolits air cool. The latest batch of ingots that I smelted tested at around 20.9 as well as the boolits that I cast (air cooled). While the harder alloy is still useable for higher pressure loads in the range of 26,000 PSI, it's a mystery to me how I ended up with such a hard alloy. What affect does zinc have on hardness, and is that a good way to determine if zinc has contaminated the batch?

[oneokie]

Place a drop of Muratic acid on your sample. If it bubbles/foams, you have zinc.
DO NOT breathe the fumes.

[Lead Freak]

I'll give it a try. I remember, back in the 50's, that my Grandfather used to make a flux to brush onto copper or steel for soldering by putting zinc window glazing points into muratic acid until it reached saturation and would not dissolve the zinc points anymore. It makes sense that this would be a good test for zinc.

Here's another question though. If there is zinc in a batch of lead, why would it make a difference if the resulting hardness is within acceptable limits?

[rintinglen]

It is not the hardness that causes grief, it is the poor fill out caused by the Zinc freezing at a higher temperature. You greatly increase the number of rejects, especially with lighter molds.
I first discovered that a batch of "Wheel Weight" metal that I had got off Ebay was zinced up when I tried to make up a batch of 358=242 122 grainers. Normally, that mold makes good boolits fast, with very few rejects, but suddenly, I was getting 50% plus bad boolits. I kept turning the pot up, added a bit of tin, fluxed repeatedly, but I still was getting poor results.

What to do?

Well, throwing out 50 bucks was out of the question, as was simply using it and muddling through. I have read that sulfur can be used to flux the zinc out but that sounds too stinky for where I live. But, the solution to pollution is dilution as the old saying goes. I spent the next few casting sessions determining how much I could have in the pot and still get decent boolits. It turns out that I can use one ingot of the contaminated to 4 ingots of enriched reclaimed boolit metal and still get good boolits if I run things hot. The mold has to be about 45 degrees hotter than normal, It works best with big boolits, and I have to add a bit of extra tin, (about 2 oz tper five ingots) but I am able to get excellent fill out and maintain acceptable production rates.

I have about 12 pounds left of contaminated FBM (Future Boolit Material) that I have been using, but I won't be buying anymore wheel weight off Ebay.

[OnHoPr]

Could zinc contamination hinder mushrooming or expansion in softer hunting boolit alloys when it comes to deer ribs or between deer ribs?

[runfiverun]

yes.
zink is a hardening agent in lead alloys.
it's soluble up to about 2% and will cast very well with no problems up to 1.5% [with a bit more heat]
over about 2% it's not soluble and shows up as oatmeal looking gunk on top of the alloy,that keeps on coming up over time,it will also strip the tin from your alloy as it floats up.
sometimes antimony will float up and it is confused as zink contamination but it can be fluxed back into the alloy whereas zink will just keep on coming up.

[Defcon-One]

If you already cast good quality bullets with it, it is not gonna be a Zinc contamination issue. It is more likely too much Antimony!

Not only that, but Zinc contaminated lead looks and acts very differently than the usual bullet alloys. If you have done a lot of casting, you'll notice the difference in the melt right off.

[Lead Freak]

So in other words, if I'm able to cast perfectly good bullets, more than likely I don't have a zinc issue? Other than the usual thin dross that shows up a few minutes after fluxing, I haven't noticed anything unusual. After skimming this light (1/2 teaspoon) of dross, I have nice smooth, shinny lead.

[I'll Make Mine]

After skimming this light (1/2 teaspoon) of dross, I have nice smooth, shinny lead.

If you're getting smooth, shiny lead in the melt, and you're below the melting point of zinc (at which point, you'd start to see smooth, shiny molten zinc on top of the lead if there's too much zinc to dissolve), then you have no more than about 1.5% zinc and you should be good to go.

Zinc above 2% won't stay mixed in lead at any temperature, but if you're running the pot hot enough to melt the zinc, they'll separate almost like oil and water -- and even if you stir in the zinc and cast too quickly for them to repartition, they'll separate as they chill in the mold and you'll get boolits that are out of balance and have hard spots.

[Patrick L]

I agree, I really don't think you have zinc contamination. You wouldn't have been able to cast good boolits if you did. The hardness could be caused by a lot of things, but I don't think its zinc.

[JonB_in_Glencoe]

How do I know if I have zinc contamination?

Do your ingots look like the ones on the right ?
these are ingots from my first zinc contamination during a smelt this summer
http://i640.photobucket.com/albums/uu127/JonB_in_Glencoe/reduced100_2661.jpg

[Lizard333]

Have you tried the muratic acid yet. It's pretty clear weather or not you have zinc.

[badbob454]

So in other words, if I'm able to cast perfectly good bullets, more than likely I don't have a zinc issue? Other than the usual thin dross that shows up a few minutes after fluxing, I haven't noticed anything unusual. After skimming this light (1/2 teaspoon) of dross, I have nice smooth, shinny lead.

the light just went on ... only problem zinc has is it wont cast a good bullet alloyed with lead in higher than 2% zinc .. otherwise a good casting alloy by itself ,, or a good hardener in very small quantitys ..... so happy casting...:Fire:

[Griz44mag]

Wheel weights are all over the place when tested for hardness. It is not surprising to see a 100% swing in hardness. Alloys that are mixed by weight depending on type of material (ie - 2 lbs of wheel weight with 1 pound of lino) is not a good method to mix an alloy. It will be unpredictable just like the original materials. The lead hardness tester is the best way to get the alloy hardness you seek for a specific operating pressure you are casting for.