Problem with my melt

[rrob692326]

Been casting for a very long time but lately my current batch of metal bought on line a few years ago is producing an oatmeal like byproduct that despite my best efforts of fluxing with commercial flux beeswax candle wax and sawdust and even skimming off of what was supposed to be already clean ww ingots the oatmeal keeps coming out in prodigious amounts. I use a home made 50 year old welded stainless steel stove with a commercial propane high pressure burner and a ladle so no high tech issues here. just keeping things simple. The bullets do come out ok and water dropped nice and hard as expected. Remelting the oatmeal skim only produces a little metal return despite vigorous fluxing, and even using sulfur, just in case it was bismuth. There is a considerable amount of loss here guys and not just a small amount or I would not be here ******** , I would guess almost a 1/4 total loss in a session, nor does it ever stop being produced from the melt. I've cleaned the pot and no change. What do you think I have here? Do you think that it might just be a temp issue? Only recently sprung for a thermometer as all these many decades I used the mold and bullet fill out and bullet condition to determine my casting temp issues. What would be an optimal temp to possibly getting rid of it, or barring that perhaps keeping in the melt from coming out? I have about 200 lbs of this lot of metal and sure as heck hate to dump it as Hawaii is a fricken bear to get casting metal for any kind of reasonable price anymore. Sorry no pics computers are not my fort'e Any ideas will be appreciated,

[NyFirefighter357]

A quick test would be a couple of drops of muriatic acid if it bubbles you have zinc in your alloy. I would contact member BNE and have it tested. What temp are you melting it to? I had an issue once where it just wasn't hot enough.

[OS OK]

Aloha, I think they say there...I use a casting thermometer in my ingot pot and keep the temperature below 750ºƒ, if I'm doing my job right and not slugging too much cold beer I'll catch it before it approaches 725º. Lately, or I should say, this last ingot pot full of COWW I purchased on line here, I came out with about a half ladle full (1.25 pounds) of that oatmeal crud in a 50 pound pot of lead. I was surprised to see it but wasn't hesitant in dipping that crud out of there quick.
Temperature control is the only way I know how to guard against it being in the mix although somewhere I've seen that up to and including a 5% blend of that stinking zinc won't hurt anything anyway.



At about 675º I'll start turning the burner down to simmer and start fluxing, but I start out with about 1/2 cup full of sawdust in the pot with the cold lead and I don't create for myself a layer of oxidized lead as the lead all comes to the melt point...I stir, scrape the first sawdust out and do it a second time...stirring and scraping well the inside of the pot and that's the end of all this fluxing business, just a pure clean melt left behind shining like a mirror.

Less than a minute before I got the camera and snapped this picture, this pot was a perfect mirror of the sky and the second story of my home above...that's how quick it will oxidize but I don't let the oxidation get me sidetracked as most of it will stir back in the pour pot with some wax.



Hope my meanderings here will help...

[georgerkahn]

I will add a caution. A buddy (Mike) rang me a few weeks ago, asking if I ever got sick from melting my alloy. Apparently, he purchased a sheet-rock bucket of COWW at a local gas station, carefully culling out ones which -- using diagonal cutting pliers -- he determined were zinc. He brought a pot load to melt, fluxing with church-candle stubs and pine sawdust, as usual, but after not that long into the session got extremely nauseas, with considerable vomiting following. He turned off the propane, and upon returning later, found similar (I don't exactly know, as I didn't see it) to what you describe as oatmeal. NOT correlating the melt with his sudden sickness, he re-lit his burner... and to make a long story short, again ended up throwing up. Fortunately, I never had this experience from smelting -- but, albeit I cast in an open garage with fans both behind and in front of me -- it was a bit of a wake-up call as to what may be in that alloy we're melting.
Just a cautionary note -- we do not really know (cadmium, zinc, arsenic,???) what might be in that which we melt... To lose a few dollars on "bad alloy" we can live with... BUT... our health/longevity?
geo

[Peregrine]

Geogrgerkahn, that sounds a lot like the result of zinc overexposure. I know that excessive intake of zinc can cause nausea and vomiting, the fact that he ended up finding 'oatmeal' in his melt collaborates that because that's how people describe their alloy clumping when there is excessive zinc around.

While your cautionary note is very much in the right spirit, and we would all do well to be cautious, as toxic as arsenic (especially if you manage to form arsene) and cadmium are, to my knowledge even large overexposure won't cause any acute effects the way your friend experienced them. I don't think your friend has anything to worry about long term as a result of that exposure, but it's interesting that he had a such a strong reaction.