When does zinc become a problem??

[wtfooptimax200]

Zinc is certainly an undesirable component in our alloys, but at what point (percentage of total alloy) does it actually become a problem? Can one 2 oz WW in a batch of 50 pounds ruin an entire smelt?

[JonB_in_Glencoe]

there was a thread a while back, where it was discussed that a small amount of Zinc in the alloy didn't effect castability and added hardness...I think it was 1 to 2 percent.

I remember thinking if I ever got some Zinc contaminated alloy, it'd wouldn't be the end of the world. with a little experimentation, a caster could just dilute the Zincified alloy with WW back to a castable amount.
Jon

[onondaga]

Can't quote the source, But I have read 1/2 of 1% is enough to significantly effect casting quality.

Gary

[fecmech]

I screwed up a couple smelts a while back with some zinc( I do about 40 lbs at a time) and just chalked up the first one as a loss. I put the ingots behind the garage. When I did it again I turned the heat down and did some skimming to get the "oatmeal" off the top of the melt. After a few minutes the melt looked a little better so I ladle cast some bullets from the pot and they came out ok. So I said what the heck and added my usual amount of tin to get a 2% mix and poured the ingots. I marked the ingots and have since used them up casting bullets for my .357 and .38 spl. and accuracy is just fine. I have had zero problems with the mix but it is a little harder, maybe BHN 16-18 air cooled. Sometime in the future I'll remelt the ingots behind the garage and do the same. Zinc is not the end of the world IMO.

[2wheelDuke]

I had some lead that I suspected was contaminated with zinc. It still made great fishing sinkers. I still have some set aside for that, much of it in the form of rejected boolits and the sprues from that bad session.

[Defcon-One]

One or two ounces in 50 pounds is not gonna cause you a major problem. One pound or more will!

I had a small batch of 7-8 pounds that was Zinced by two or three Zinc weights a while back (my error). So, I took a risk and skimmed off all that I could and then added an equal amount of good WW lead and 2% tin. It was then made into 16 one pound ingots. I know it was Zinced because the dross tested positive the next day when I got some pool acid.

Just today I cast the last of that batch of lead into the nicest looking 9mm bullets that you have ever seen. It is obviously better to not have it, and I have taken precautions to make sure I never get Zinced again, but it is not the end of the world either.

[shotman]

your main problem is getting it to mix at normal cast temp. second is , if you use AL molds and raise the temp you will get galling . as said a little dont hurt
If you use pure for HARD cast use a steel mold

[barefoot1]

I am new to casting the last few weeks and have good results so far with my Lyman handgun molds, How do you sort out the zinc weights b4 melting?

[bumpo628]

I am new to casting the last few weeks and have good results so far with my Lyman handgun molds, How do you sort out the zinc weights b4 melting?

There are a few ways to do it:
Many are marked with "Zn"
When dropped, they make a ringing noise, not a thud.
When cut with a pair of wire cutters, you'll barely mark the surface.
In my experience, the zinc clip-on weights seem to be cleaner (although that can easily change)

With a little practice, you'll get most of them by sight. Sorting the clip on weights is harder than the stick ons though.

[dieguy59]

I think I need to try fecmech's idea. I may not have too much 'oatmeal' to scoop off, but I should try something. Is it essential to add some tin?

[fecmech]

I don't know if tin is all that necessary but it can't hurt. Keep the temp low and skim the junk off and try some bullets ladle casting. If that works go for it, if not add the tin.

[badbob454]

if your bullets dont fill out or have wrinkles , you should add up to 2% tin. or increase the casting heat .