Beginner poroblem: zinc...

[Etienne Brule]

Hi,

I am new to round ball casting; up to now, I have made about 500 RB. Everything seemed to go well in a "pure lead" world.

This weekend I bought 50 pounds of lead at my usual dealer: "Pure Lead".. as usual.

I began the cast at 800*F... as usual; everything was goeing as usual; then I began to pour in Lee lingot mould.

What a surprise; the metal was brittle and white shiny... My God... grrr..

I looked back at the stuff that I bought: well, with my beginner eyes, it seems like pure lead...

All the 50 pounds got out the same way.

So I surfed on the web to find what it could be: I looked at melting temperature of metals in the range 500*F to 900*F ( remember that I am a beginner...).

So this morning, I casted that stuff again but à 600*F..... SURPRISE...

I had about a few onces of lead and a kind of blue gray stuff:

I concluded that it was ALL Zinc (or I think so).

Tomorrow I will go to see my dealer.... and see what he will say.


Question: is there a way to know BEFORE buying if it is all ZINC ( a real beginner question, I guess.)



Thank you for your attention.

Etienne Brule

:castmine:

[Bent Ramrod]

Etienne,

The way I would do it would be to put a drop of hydrochloric acid on the sample to be tested. "Muriatic acid" that is used for swimming pools and descaling is fine. The zinc should react quite vigorously, fizzing as it bubbles off hydrogen, and dissolving completely in the liquid, while the lead response will be sluggish, with much slower bubble evolution and a slow formation of crystals of lead chloride.

I haven't handled a great deal of zinc, but it tends to be shinier than lead and quite a bit brighter. But I couldn't say that I could tell one way or the other just by hefting an anonymous ingot. Sorry to hear you got stung; hope your dealer makes good.

The one time I think I had a small amount of zinc contamination in lead, the metal melted, but it was slushy and uncastable.

[Ohio Rusty]

I do a couple of things to test lead. If the edge slices easily with a knife and it scratches easily with a thumb nail, then it it most likely pure lead. Another thing I do with round ball to test them is I drop them on a cement floor from about the height of your pants pocket. Pure lead round ball won't bounce. They kind of stick in place and maybe roll a bit. That is because the lead flattens on one side. A harder alloy of lead will not want to flatten and will slightly bounce off the cement when dropped. Another test you can do is mould the lead into an ingot and holding it up, hit it lightly with some metal tool. A pure lead ingot won't 'ring'. Pure lead will give you a dull 'thunk' while wheel weight ingots or alloys give a light 'ring' sound when tapped. Zink is really hard and is difficult to cut or slice into with a pair of wire cutters. Also the melting temperature is a good clue if you know what temp you are melting at as zinc doesn't want to readily melt at 600 to 650 degrees, while pure lead turns to liquid. Hope some of these tips might help.
Ohio Rusty

[Etienne Brule]

WOW,

That is exactly what I wanted to know.

Thank you so much for the attention.

Etienne Brule. :-D

[OeldeWolf]

I cast for both round ball and centerfire. Pure lead is, of course, the hardest to come by here in CA. With the difference in melting temperatures, is it possible to seperate the zinc, and other alloying ingredients out? It looks possible theoretically, but what about practicality in the real world?

OeldeWolf
who may yet be kicked out of the Republik of Kalifornia for owning too many firearms

PS: looking for a mold for .25 ACP bullits

[Bent Ramrod]

OeldeWolf,

It's logical to think that a piece of zinc would float on melted lead and take a while to melt or dissolve in the lead. I've never deliberately tried to do this, so I can't say whether this is what happens or not. I think the typical situation is that an anonymous pile of scrap metal is melted down, stirred around to get the last of the lead down into the molten liquid, the mess is fluxed and stirred some more, the junk is then skimmed off and thrown away, and the pot of lead then essayed for castability by starting casting. From the result I had, it appeared that not much zinc would have needed to dissolve to ruin the pot of metal.

Since zinc is much more active than lead, there should be ways of oxidizing or otherwise removing it from the rest of the metal, but any I can think of are kind of beyond the scope of the home-caster and his setup, and definitely more hazardous than 10 or 20 pounds of lead would be worth.

[Etienne Brule]

It's logical to think that a piece of zinc would float on melted lead and take a while to melt or dissolve in the lead. I've never deliberately tried to do this, so I can't say whether this is what happens or not. .

Hi,

I am just a casting beginner; but I realized that Zinc does not dissolve at 600*F.

BUT, at 600 *F, Zinc is not as solid as we could think; it is a kind of "slusch" not liquid but not so solid; it does not float... And it is "mixed" with the liquid lead.

It is quite a mess; almost impossible ( with my little means ) to take it off completely.

Zinc is a NO WAY to go.... ( as far as my experience is ).

BTW, my dealer was impressed with the muriatic acid test and change the whole batch for "pure lead" with a 25 pounds of "compensation".


It is just my 2 cents (for whatever it is )...

Etienne Brule.

http://i16.photobucket.com/albums/b14/geraldbergeron/calumet.gif

[Andy_P]

If you run a "production line" kind of smelting operaton where you are continuously skimming and ladling to your ingot mold as soon as you have a melt, and then immediately adding wheelweights such that the melt becomes "slushy", you will not melt any zinc.

Zinc is consideralbly less dense than lead, and has a 165 degree difference in melting point. This gives sufficient separation from the lead to ensure that they float on top intact and plenty solid along with the metal clips, rubber stems, dirt etc. I have done many hundreds of pounds that way with no problems. If however, you (for some reason) let the melt sit over a hot flame for many minutes, then you will have the zinc melt into solution.

I no longer even try to separate zinc from non-zinc. I do separate stick-on from clip-on, and remove the junk, but since so many wheelweights that appear to zinc are lead and vice-versa, it is futile to try.

You'll work up your own system, but IMO, the thermometer is unecessary if you skim and our immediately after the melt goes from slush to liquid, and when done, add more wheelweight to get the slush back.