bad issues while smelting lead andneed help

[latesvak]

so im melting down a 5g bucket worth of ww like i have done so many other times . im cooking them down in a c.i. dutch oven (6" tall and 14"wide) over a turkey burner . not my first rodeo doing this by any means . so the first two melts went fine with me getting 12 1.5 lb ingots per pot . previously i had sorted and pulled all but the lead ww vs others. if i think it might not be lead i scratch it on a file to rough it up or i will dent check it with some pliers just to double check. so im pretty sure all the bad ones are out .
well after getting this 3rd pot melted down and getting ready to start skimming the dross off it just looked a bit off to me . then after getting all the clips out i skimmed it off and added some wax then waited for it to burn off then scrape all the sides and bottom as usual. then it got an almost iridescent color to it . like some purple/orange/yellow layer on top. wth is this im thinking? so i skim it off and fluxed again. i tried 2 different waxes and sawdust and this layer of junk kept coming back . any help would be greatly appreciated .

thanks

latesvak

[badbob454]

im thinking the melt is getting too hot if the color is just paper thin , should be oxidized from the heat of the melt if it is thick and oatmealy may be something else

[leadbutt]

From my limited experience color is temp related.

[Ben]

Yes, it is a temperature issue. Way too hot.

[evan price]

Rainbow colors are an indicator of the pot too high and more lead in the alloy vs antimony or tin. Nothing wrong, lower the temp and all will be fine. 700 degrees max.

[sqlbullet]

Too much heat. I find I have to cut my heat as I cast ingots, then turn it back up again when I add lead back to the pot. I generally cast about 60 one lb ingots and then add 60 lbs of lead to my pot.

I also start casting as soon as I can. I hate waiting on ingots to cool, so I have the molds sitting on a soaking wet towel in a cookie sheet. By the time I cast the end of the second mold, the first one is set up enough I can dump it. I can get about 80-90 lbs an hour this way.

[latesvak]

i thank you all for the input and i did not think i had it to hot but i will try some more later tonight with a lower temp and see how they come out . but after the ingots cooled off they look just like the other 2 batches i did . and if i can figure it out i'll try and get some pics up and show you what i mean. thanks again .



latesvak

[Gtek]

+1 on the 700 degrees, that is my do not exceed mark smelting. All the colors are from oxidation on surface. A thermo is money well spent. Gtek

[sqlbullet]

Also, a thermometer will save you if you ever get one of those evil zinc WW in the mix. It won't melt at the lower temps.

[Defcon-One]

....purple/orange/yellow layer on top.....


Everyone else already said it, but it can't be said enough. This almost always means lead oxides! Your melt is way TOO HOT!

[SkookumJeff]

Not to hijack this thread, but I recently had a pot of lead get way too hot. I turned on my pot and while waiting for it to get up to temp I started messing around with a reloading press setup, and sort of forgot about the casting pot heating up. When I checked it, the temp was over 1000 degrees F. (my gage was pegged). My lead looked REAL BAD. I lowered the thermostat and added more ingots to try to cool the alloy down to casting temp. Once it got down to 800 degrees F I fluxed it well with hardwood sawdust, mixed it well and after the alloy looked normal again I started casting.

My question is, did I do any damage to the alloy? Does overheating cause any irreparable damage? My cast boolits seemed fine, although frosty. Just curious...

[Wayne Smith]

Nope, nothing permanent. By fluxing with sawdust you returned the oxides to the melt, so all is good.

[Tammany42]

The issue is the temp at which lead vaporizes and is really hazardous.

[sqlbullet]

The issue is the temp at which lead vaporizes and is really hazardous.

The boiling point is over 3000°*F. You will have very little lead vaporization until your cast iron was near or at it's melting point of 2800°.

The larger health concern I see is the lead oxide dust that may be lifted off the melt if using a dry flux alone, or if the flux is flamed before stirring some. This dust the biggest reason to have an exhaust fan to draw off any fumes.

[Defcon-One]

....My question is, did I do any damage to the alloy? Does overheating cause any irreparable damage? My cast boolits seemed fine, although frosty. Just curious....


You might have turned it into GOLD, but I doubt it!

1,000 degrees F is not hot enough to do any real damage! It takes about 3180 degrees F to fume out (Boil) Lead, which could be a risk to you not the lead. The frosty surface is from pouring the lead a bit too hot.

Cooling it down with a couple of new ingots and fluxing was a smart and appropriate response!