Zinc - fix by alloying with pure metal?

[HNSB]

(This is kind of a long post... There is some background information at the beginning, but if you're in a hurry, you could skip down to where it says "ANYHOO" below)

I am pretty new at all of this....

When I first started melting wheel-weights, I was unaware of the problems with zinc. I just got my kettle good and hot and waited for everything to melt down. Then I'd cast ingots.

I currently have about 65# of ingots on my shelf, and about 40# of bullets cast for 9mm, 40, and 45. I did seem to have problems getting the 9 and the 40 to cast well. The mold seemed to need to be VERY hot to get good fill out. The 45 seemed easier. At the time I just figured the problem was that the smaller mold cavities held less lead, and thus took longer to heat the mold. (All of these molds are Lee molds for the micro-groove bullets, btw)...

Anyhow, it always seemed like as long as the mold filled, I had good fill out of the bullets.

Fast forward to this week. I just bought a mold for my 357. I wanted to do GCs on these, and so didn't go with a micro-groove type mold. Unlike the micro-groove molds, the bands on this one have a more square edge profile. I was having a heck of a time getting fill out. I only dropped about 80% of the bullets I poured (after the mold was heated sufficiently), and after sorting only kept about 80% of what I dropped. I had a lot of problems with rounding of the bands and on the bases. I am sure the other boolits would have had the same problem, but the rounded tumble-lube bands prevented it from being apparent.

I just chalked this up to inexperience, and not having my mold hot enough. Now I am wondering if I have a zinc problem...

One other thing I did (as I will be using these for hunting) I did a crude test for expansion, by setting one of the boolits on concrete, and smashing it with a hammer. It was MUCh harder than I expected it to be. It deformed very little upon being struck. I water dropped the boolits when I cast them, but I still didn't expect them to be that hard... That also leads me to believe that I have some zinc...


ANYHOO...

I read about using sulfur to get zinc out of the alloy. I am going to try that.

One other thought that I had though was to just re-melt my ingots, and mix in a little tin and some pure lead (which I have a lot of, from a friend that remodeled a dental clinic and gave me a bunch that was in the walls).

Thoughts?

[waco]

i think you would know if you had a zink problem
you would get a purple scum on the top of your melt, and the alloy just would not seem to melt right
as far as the fill out not being good......lead not up to temp.
mold not up to temp
mold not clean
not pouring the lead fast enough?
i dont think zink is your problem
keep at it!
hope this helped
waco

[sagacious]

Halt! Stop! Hold on a minute before you start fluxing with sulfur, or entertain any other "fixes" that you have zero experience with!

From your description, I do NOT think zinc contamination is your "problem."

Zinc has very rapidly become the new boogeyman, and the conclusion of late has increasingly been,
"My lead isn't doing what I might have expected.... must be zinc contamination!"

I have seen and worked with lead alloys contaminated with zinc. Zinc in lead generally causes extreme problems with mold fill-out, causes the cooled bullets to look like they have a 'cottage-cheese' appearance, especially at the sprue end of the bullet, and the zinc causes an aggressively-forming frothy scum dross on the surface of the melt. The frothy scum is a good indicator. Lead contaminated with zinc often presents serious or impossible challenges when pouring small castings, and it's not generally just a little bit problematic.

Your primary concerns appear to be twofold. First, you are useing ww lead, and that alloy may require a percent or two of tin to get good fill-out in some molds. This is common.

Second, your ww bullets are harder than you might have expected. This is also common. Well, you water-quenched them to make them hard, but you're surprised at the hardness. This concern answers itself-- ya made 'em hard, and they are. Done deal. Good work. :)

Now, as for the bases not filling-out and being rounded, that is likely to be solved completely by adding some tin and keeping your molds hot and at a consistent temperature.

I would urge those who are new at pouring lead to not just automatically assume that their problems arise from "bad lead" or the devil of zinc contamination. Make sure you're doing everything right first, and only then start looking elsewhere for your fixes.

I hope this helps. Keep at it and some of the mysteries will dissolve, and you'll be pouring great bullets every time.

[captain-03]

When I first started melting wheel-weights, I was unaware of the problems with zinc. I just got my kettle good and hot and waited for everything to melt down. Then I'd cast ingots...Thoughts?

I, too, did the same thing when I just started casting. I know that I have several batches of ingots that contain Zinc. I know this now because I can remember that there were WW that just would not melt down with the others - I ran the temp up until I got them to melt!

Problems - yes, I have had problems with some of my casting; however, I do can not and do not attribute them all to the Zinc ..... I have found what others have said above to be true - temp of alloy and mould and the addition of a little tin has a lot more to do with proper fill-out than a little Zinc in the mixture. The only real problem that I have yet to overcome using these batches which contain "some" zinc is with my .225 22cal moulds ... I have to use lino or virgin WWs with tin in order to get the fill-out I am looking for.

Point -- Agree, zinc is not the problem in most cases even if your mix does contain a little of it ....

[HNSB]

What you guys say makes perfect sense. Thanks for the advice.
I can relate to this with archery. I know people that have won national tournaments with equipment that was severely out of tune. I also know people that start wrenching on their perfectly tuned bow everytime they have a flier. It's always easier to find something to blame for the problems that we cause for ourselves. That can lead to an extreme paranoia about problems that don't exist.

But, you have to admit... To a newbie reading this forum it would be easy enough to believe that zinc in your melt will cause bad bullets, hair loss, kidney failure, impotence, and bad breath.

[docone31]

Oh well.
You did not mention it, but I suspect you are useing Lee Molds. I like them personally. They do exactly what I want them to do.
They need to be hot. Real hot. Good fillout comes out from an hot mold. Rest them in the mold about 1/2 minute before casting. Even with some zinc in there, you should get decent boolitts.
I deliberately mix zinc in my alloy. I try to get 2%. I paper patch so the hardness is not an issue. They fire real well. I use them in my .45ACP, 9MM, and .357s. 2% is a about all I can add to my mix to get good overall casting.
Now, I do have a real mix of zinc. They have the classic frothy top, the lower layers melt, the upper layers stay frothy.
I am diluting it with pure lead. I get about four or five Roof Boots a week from a contractor. My muzzle loaders love it, and since I have almost exclusively switched to muzzle loader my Wheel weight is untouched. I am blending my zinc with the pure, at about 20-1. From there I am blending it again the same with some wheel weight. I then mix it in the pot at about 1 ingot to a full pot. It goes unnoticed.
With Lee Molds, you should also soak them in mineral spirits for at least two days. From that point they should be degreased and ready to go. Get them hot! If they are too hot, the sprue will be too loose too long. Dump that one out, set the mold down, and resume after taking a break.
I like to go by a six second rule.
I fill the sprues, then count to six. They should be hard at that point. I then cut the sprues, dump them back in the pot, and dump the castings in the water.
I refill, then do it again.
Good luck.

[leadman]

New Lee molds can be very difficult to get clean enough to cast good boolits. I have been using carb cleaner or acetone and scrubbing with an old toothbrush. Then heat it up good in the alloy and problem is usually gone.
If I still have problems casting with a well heated mold with a known good alloy I will cast a boolit for each cavity, drill a small hole in the center of the base and screw in a drywall screw. A little mix of water and scouring powder as a paste on the boolit, spin slowly in the cavity with cordless screwdriver just enough to change the color of the metal in the cavity.
Only do this last operation as a last measure.

[fredj338]

Try holding the spout in contact w/ the sprue plate for each fill, then back off & make a spure. THis sort of pressurizes the lead pour & helps fill out.

[Rocky Raab]

I went back and re-read the metallurgy article in the Lyman Cast Bullet Manual (3rd Edition) last night to be sure I remembered it correctly. The bottom line is that they say it is not possible to get zinc out of an alloy mix, and that the mix is ruined for bullet use.

I'm NOT a metallurgist, so I can't argue or even discuss the issue with anyone who disagrees. I'm merely passing along what Lyman says.

Personally, I can't get wheelweights locally (all the tire shops are under contract with a metal dealer). But if I could, I'd follow the Lyman advice and smelt them at the minimum temperature that allowed lead to melt, and carefully pick out anything that didn't melt. If there were a zinc weight in there, it should float and remain unmelted if the temp is below 650 or so.

If I did have a zinc-contaminated alloy, I'd either make fishing sinkers or sell/trade it to the metals dealer.

[Matt_G]

I went back and re-read the metallurgy article in the Lyman Cast Bullet Manual (3rd Edition) last night to be sure I remembered it correctly. The bottom line is that they say it is not possible to get zinc out of an alloy mix, and that the mix is ruined for bullet use.

I'm NOT a metallurgist, so I can't argue or even discuss the issue with anyone who disagrees. I'm merely passing along what Lyman says.

Rocky,
Here are three recent posts you may find interesting.
Sciguy posted about a method of removing zinc using sulfer.
http://castboolits.gunloads.com/showthread.php?t=62957

Then arcticbreeze posted about messing up a batch of lead with zinc.
http://castboolits.gunloads.com/showthread.php?t=63044

He tried the sulfur and reported back in this thread. Short story, it seems to have worked.
http://castboolits.gunloads.com/showthread.php?t=63082

FWIW

[Rocky Raab]

Thanks. I did notice those threads after I posted.

As I said, I'm not smart enough to even discuss it from a technical standpoint.

[HNSB]

Thanks for your help everyone.

Instead of freaking out about zinc, I stopped at the hardware store today and got some 95% tin, 5% antimony solder.

Mixing that at a little under 2% with my wheel-weight melt fixed my problems. Tonight, about 95% of my dropped boolits were keepers, and even the throw-backs were as good as what I was keeping before... Apparently a little tin is a good thing.

Thanks everyone for your help. It would have taken me months to figure that out on my own, if I would have even figured it out at all..