Why not use Zinc to make lead harder?

[TylerR]

I am wondering why you cant alloy a small amount of Zinc in with the lead to increase the hardness. I am sure there must be a reason people dont do this. I have just never known why.

[docone31]

I do.
With my paper patching, it either helps, or does nothing negative.

[runfiverun]

you can do it.
if you use too much it has a tendency to make a mess of the whole batch, including making you have to really clean your pot and your mold.
a small percentage will harden lead just fine.
the refiners use zinc to clean "impurities" from lead. impurities including tin and antimony.

[44man]

Zinc does not like to stay in alloy and migrates to the surface. Boolits will not fill out and will look like a galvanized rain gutter.
If you slowly bring the lead to the melting point, zinc will float so it can be removed. 600* works best. You will also lose some antimony and tin to get rid of the junk. One zinc WW can ruin a whole pot of lead.
Best to stay away from the stuff.
A trace will not hurt but the amount is so small it will not harden anything. Use antimony.
When smelting WW's, keep the temp low so anything that floats can be skimmed off.
I don't want any part of zinc in my alloys. Zinc loves to combine with the precious tin and keep it from allowing antimony to alloy properly. Tin alloyed with antimony might allow zinc to suck both metals out of alloy with lead too.
There must be some here with knowledge about alloys that can really explain what happens.
Zinc is NASTY! [smilie=1: