gold scum

[Dr.Doug]

Hi Guys,

I was casting round balls last night, and noticed a golden "scum" on the surface of the molted lead. It didn't seem to bother the casting process, and Marvalux didn't remove it. I was using dead soft lead from lead shielding that had been used around an x-ray room. When left undisturbed for a time, the scum seemed to oxidize further and began to look like rust. The balls are within 1 grain of those I cast a few day before (with different lead), but I'm curious.

Any ideas?

Thanks,

Doug

[waksupi]

Doug, that is most likely just tin oxidizing on the top of the melt. Leave it there!

[Buckshot]

...........Dr Doug, welcome to the board. Maybe you can help me out? I have this pain that........... well never mind. Maybe you're not that kind of Dr :D.

Might be tin as Waksupi suggests. Regardless it's a sign of heat. No problem except it will build up as you dipper cast (if you are) as you're exposing fresh lead to the oxygen in the air each time you dip. If a bottom pour, it should just remain on the surface. As the level in the pot lowers it may want to cling to the side of the pot some.

If you should ever batch scrap lead, say with a turkey deep fryer deal, you will get the yellow scum and also it will turn shades of iridescent blue. JUst hot!

...............Buckshot

[Dr.Doug]

Thanks for your advice, gentlemen!

Buckshot, regardless of what your pain is, I bet it can be cured with a new mold or two! (at least that always makes ME feel better)

If it's tin, I'll save it for non-muzzleloader projectiles.

I hadn't thought about heat- I did have it turned up pretty high for no good reason. I'll cool it down next time and see if it changes.

I am a dipper, rather than a bottom pour kind of guy. If it's oxidaton, wouldn't Marvalux remove it?

I blended some for 20:1 alloy (with tin), and did not notice the same golden scum.

Oh, darn, I'll just have to shoot these, then cast some more...

[9.3X62AL]

Dr. Doug--

Welcome to the board, and thank you for posing the question about the colors atop the melt. I've seen the same sort of effect now and then, and wondered what it was. As long as it ISN'T something evil (like ZINC, for example), I'm a happy guy.

[Cherokee]

Like others have said, just heat. Turn it down some next time.

[BruceB]

I've only seen the gold/blue colors when casting what is, for all practical purposes, pure lead.

Lead sheeting, cable sheathing, and stick-on wheelweights typically show the coloration on the melt at my normal high casting temperature, which is 870 degrees in my RCBS furnace.

The most recent occurrence was a few days ago, when casting .416 softpoints with a can of molten pure lead floating on top of the WW in the pot's bowl. Even some of the bullets themselves showed gold/blue coloration on the soft noses. I don't believe this phenomenon is is tin-related, since it manifests itself only in the very softest (highest-lead-content) melts. I expect it MIGHT show up in such low-tin alloys as 30:1 or something, but it certainly doesn't appear in harder mixes, in my experience.

[PatMarlin]

Could be gold in them thar lead... :shock:

[Dr.Doug]

PatMarlin-
Gee, I hope it's not gold- I just want PURE lead for my round balls. Darn contaminats! :)

Doug

[felix]

Doug, are you talking lab grade lead? ... felix

[Bent Ramrod]

Pure lead melts at higher temperatures than most of our alloys, and is more prone to oxidation at the hotter temperatures. The yellow is PbO, called massicot, which upon further heating and melting turns darker yellow and finally to a reddish color, which is known as litharge. This mixture is probably the "gold" that we see. Further heating turns the oxide to minium, or red lead, which is Pb3O4. I suspect this latter material is mistaken for rust when we clean out our lead pots, as it looks very much like iron oxide. I find it stuck to the sides of the pot when I scrape them down. Don't breathe or otherwise ingest this dust.

[fiberoptik]

Then don't buy them remington RB's, as they're already gold color'd!

[Dr.Doug]

Bent Ramrod-
The oxidation you described is exactly what I observed. Thanks for solving the mystery!
Doug

Felix-
I doubt it's lab grade lead, but I suspect it's pretty pure (other than a lot of drywall dust!)
Doug

[Headstamp]

"The yellow is PbO, called massicot, which upon further heating and melting turns darker yellow and finally to a reddish color, which is known as litharge."

So people with a reddish complexion are basically, "Lithargic"? ;-)

[Dr.Doug]

Hi folks,

I finally got around to casting some round balls with the lead I asked about. Keeping the heat in a normal range showed no discoloration, but when I cranked it up and let it sit for a period of time the colors returned.

Thanks again for all your help.

Doug

[versifier]

These different oxides of lead were for many years used as oil paint pigments. Too many artists exposed to them have had to change to less toxic alternatives. The oxides are definitely much more toxic than metallic lead, and like it can be ingested, but unlike it, also inhaled or absorbed through the skin. Nasty stuff, but no one's tempted the lick the bowl when the casting pot is empty. Still, it's another good reason to be careful about washing your hands and being careful how you dispose of dross and waste.

[StarMetal]

Washing your hands is probably one the most healtiest things you can do, not only when handling lead, but also for cold and flu prevention. When you handle lead, especially when your fingers look lead color, don't eat anything using your fingers, don't pick your nose, don't scratch your head. It's not a bad idea to wear gloves when handling lead such as casting, except in reloading unless they are some kind of thin glove.

Joe

[kodiak1]

bruceb you mentioned stick on wheel weights from what I have heard and please correct me if I am wrong but that stuff is bad bad bad for you!!!!!!
Thanks Ken

[BruceB]

Kodiak, sir;

As far as I'm aware, the stick-ons are just another lead alloy which is much softer than the clip-on "normal" wheelweights. They are soft enough that I treat them as pure lead, and they serve me well in the normal roles for a dead-soft bullet material. That is, I use them for round-ball in percussion revolvers and muzzle-loading rifles, and occasionally to soften-up some WW alloy for certain loads in my Sharps' or .416 Rigby.

I do my smelting outside, so fumes from the glue and backing material of the stick-ons don't bother me.

Based on using them for quite a few years without harm, I'd say the stick-ons are quite acceptable in the pure-lead role. What have you heard, that says they're
"bad, bad, bad for you"?

Curmudgeon, Deputy Al and I passed through your area back in November; we'd been hunting around my brother's place west of Grande Prairie, and we're GOING BACK THIS YEAR!!!! Congrats on your new guvmint, too....it's a long-overdue change. Hope they can do some good as a minority, and then get a working majority a couple of years down the line.