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JimmyBallew
08-03-2006, 09:23 PM
I've been getting a lumpy, oatmeal like dross on my melt that will not melt away, even at close to 900 degrees. It averages between 1/4 and 1/2 inch thick on top of a lee 10 lb pot. Is this zinc? I've been skimming it off the top of the melt and it dosen't reappear.

Bent Ramrod
08-03-2006, 10:51 PM
Jimmy,

Does the stuff persist even after you've fluxed the metal? My one episode of what I suspect was zinc contamination had the entire mass of lead turn into a silvery slush that would not pour through my ladle. I often get a silvery lumpy surface dross similar to what you describe after melting any highly alloyed lead, like linotype or salvaged commercial cast bullets. Skimming it off makes the bullets softer; the addition of flux makes it disappear back into the lead and the bullets are harder. Extra heat won't do much more than oxidize this dross and the underlying melted lead as well.

JimmyBallew
08-03-2006, 11:15 PM
Jimmy,

Does the stuff persist even after you've fluxed the metal? My one episode of what I suspect was zinc contamination had the entire mass of lead turn into a silvery slush that would not pour through my ladle. I often get a silvery lumpy surface dross similar to what you describe after melting any highly alloyed lead, like linotype or salvaged commercial cast bullets. Skimming it off makes the bullets softer; the addition of flux makes it disappear back into the lead and the bullets are harder. Extra heat won't do much more than oxidize this dross and the underlying melted lead as well.

Yes, it's still there after the metal is fluxed, Marvelux does nothing to it. The melt will still pour thru the pot, it just has this lumpy surface. The metal came from wheelweights that I personally smelted a few years ago. I've had the same thing you have described, but it was from some sheet lead that someone gave me, it was supposidly used to waterproof shower stalls under tile.

dragonrider
08-04-2006, 09:43 AM
First things first, Welcome to the forum.
I do not believe it is zinc, at 900* zinc would have alloyed with the lead and it would not be floating on top. It is probably just crud and dirt. If it reappears after fluxing then you don't want it there, skim it off and flux again.
Also get rid of the marvelux, it will rust your pot because it attracts moisture, at least don't use it in your bullet casting pot. I find that sawdust works the best. I dump a couple of tablespoons in my pot then let it heat up and then stir things up a bit until it is completely carburized then I add more, I leave all the carburized wood in the pot, it serves to keep the surface from oxidizing, when I am ready to add more lead to the pot I skim it off, add lead and do the sawdust thing again. My bullets and my pots are cleaner than they have ever been.

Sven Dufva
08-05-2006, 02:25 AM
My experience of zinc in alloy is that the result of casting are a disaster. When the bullet removes from mould you can notice parts of bullets who have schrinked. If you a litle zinc well blended in alloy, the hole bullet will be smaller in dia not so mutch but you lose in accuracy.
So my tip is loock at the result, is bullets nice loocking and you have good accuracy then you have good alloy.

JimmyBallew
08-05-2006, 06:49 PM
Thanks guys, I was kinda thinking that it was just some trash in the melt. The metal was making good boolits, nice and shiney and filled out at about 600 0 650 degrees. I've got to repair my lee pot before I can make any more, I think I've got a damaged heating element from a previous repair. It won't hold the melt above 600 degrees with the thermostat wide open without help from a propane torch. I've got an element and a thermostat on the way.