Problems with new lead alloy

[Greg Skinner]

I recently acquired about 100 lbs of lead from a gun club that sold it as reclaimed shot that had been melted and poured into ingots. My understanding is that shot is lead with some antimony, the percentage depending on whether it is magnum shot, chilled shot, etc., but with little or no tin. Therefore, I bought some tin to add, figuring one or two percent would improve casting qualities.

For the first batch I melted 20 lbs of ingots and added 0.4 lbs of tin nuggets. I fluxed it thoroughly but no matter how much I flux there still is a thick layer of "oatmeal-like" consistency metal floating on top. When the temperature is hot enough for good casting the color becomes sort of yellowish-purplish. I casted a couple of hundred boolits and they seemed to cast all right but I'm wondering about the quality and uniformity because of the unknown metal floating on the surface.

I've cast quite a few boolits in the past using Roto Metals hardball and Lyman No. 2 and experienced no problems.

Anyone have any thoughts on what is floating on top and what, if anything, I can do about it or whether to just ignore it?

[sqlbullet]

What temp is the pot?

As I recall both hardball and No.2 are eutectic alloys, meaning they don't really have a slush stage. But other ratios of lead/tin/antimony do have a slush stage, and more heat may resolve your issue. Unless/until I know the temp, I can't comment on that however. About any alloy of lead/tin/antimony should be fully liquid by 650° F. Below that point you may get good casts with a hot mold, but might still see some slush at the top.

As a second, unsolicited piece of advice...I always cast with what I have without addition until I identify a deficiency I need to correct. You alloy may have needed tin, but it might also have cast fine boolits without it. To each his own, but lots of guys here, me included, cast lots of boolits that shoot just fine out of whatever scrap we have. I only spend money on additional tin if I can't get good fillout with a hot mold and a 700° pot. Or if I am after some specific characteristic tin will add to the boolit, such as better terminal ballistics in a game boolit.

Hope that helps.

[jsizemore]

If your temp is high enough and you've fluxed/reduced throughly with all the necessary stirring and scraping of the pot, your probably seeing graphite that the club didn't clean/flux from the reclaimed shot.

[fredj338]

When working with essentially unknown alloy, I don't add anything to it. Fire up the pot, get the alloy to a temp & start fluxing. You really have no idea what impurities are in the ingots. Then if you want to add tin, go for it.

[Greg Skinner]

Thanks for the replies. I don't have a lead thermometer so I can't monitor the temperature. I'll try some of the alloy without adding any additional tin and see what happens. With the other known alloys I have been using I do see an accumulation of dark gray power (graphite?) over a period of a couple of casting sessions. This powder settles out on top when the lead cools and I can dump it out. The sludge material I am seeing in my unknown alloy does not separate out when the pot cools but hardens with the main material as it cools. I'm not sure of the hardness, either, but I am procuring a means of testing and that might help me figure out what I can best use the alloy for.

[fredj338]

Fluxing is your friend with unkown alloy.

[gtgeorge]

I had the exact same experience with some supposed WW lead bought from a member here last year and only way to use it was to turn the temp way up and it left nasty deposits everywhere it was used. I finally gave up on it and went to lead from a foundry and stick to that as it is a pleasure to use and clean. I am currently cleaning up the last pot it was used in.

I also tried thinning it with good alloy but the sludge followed through ruining every batch.

[lwknight]

I got some scrap that made a thick sludge on top that would not reduce or flux in. I skimmed it off several times
till finally it was good enough for fishing weights. Actually , I think it would have cast bullets after adding tin.

Anyway the sludge that I skimmed off was about 20 pounds so I remelted the sludge and fluxed that. It yielded 15 pounds of good lead and 5 pounds of some grey crumbly powdery oxide junk. No idea what it was but it can be removed with patience.

After assays if my various mixes , there were only minimal zinc levels in some samples so it was not zinc related. My highest zinc level was something like .4 percent and it did not hurt the alloy one bit.

[tomme boy]

It is lead oxide. Smash it against the side of the pot. Takes awhile but it will reduce back in. It will turn to a grey dust as you keep doing this. I ran into a bunch of virgin shot that was very old and stored in a wet garage and got the same thing. Don't thown it away just take your time and try to fix it.

[WILCO]

. I don't have a lead thermometer so I can't monitor the temperature. I'm not sure of the hardness, either......

You can't dance if you don't have the right shoes. You need the correct tools if you're going to blend your own alloys. To do so otherwise if a waste of time and materials.