Woe and Intrigue: Thick Brown Dross

[Woodsroad]

So, it's a nice day and I decide to smelt the soft lead sheet, pipe and ingots from the scrap yard.

I almost fill the large cast iron dutch oven with melt. There is not a lot
of dross, but what is there is a very fine, dark, heavy powder, difficult to
remove, even after fluxing with Borax and then beeswax. Clearly, there is
lead intertwined with this stuff. I manage to remove it all.

I cast six muffin tins of ingots, they look good, and decide to add more lead to the melt. After the pot is about half full, one leg of the burner begins to rapidly sink into the dirt. I guess the dirt under the burner had melted and that leg was sitting on ash or something. I manage to remove the kettle from the burner, but, in doing so spill a good bit of melt on the dirt. I wasn't hurt, I had on thick boots
and pants and gaiters. I get the kettle on blocks and continue with the melt.

After I get the melt back to around 650ºf, I peel the lead off of the dirt and add it back to the melt. There is a lot of crap stuck to it, since I melt next the
burn pile. I continue adding sheet lead, removing the fine, heavy powder as
I go. One extra thick sheet, marked "low level radiation shielding" takes a particularly long time to dissolve, and some of the thin sheet seems to float a little, but does melt. I assume that the really thin stuff has a heavy coating of oxidation.
I flux again and begin seeing a pretty weird thing: Brown/red/green dross "bloom" starts rising out of the melt. I remove it. It is very heavy, with a consistency of dirt. Molten lead can be seen trapped in it. the melt temp is now at 780ºf, and I turn off the burner.

As I remove it, more rises to the surface. It's looks like that this is an oxide, forming as the surface of the melt is exposed. I realize that I could sit there and remove it all day. It looks like rusty dirt, but is not magnetic. If I scoop some
up with a strainer, as the molten lead drips out of it, it leaves a
stalactite of slag, which begins to glow and burn off, giving off a thick
yellow smoke. I do have a respirator on.

What the &^%$# is happening here?

I cover the pot and turned off the heat. I wash all my clothes and throw out the gloves that had on.

Any ideas?

Thanks!

[44man]

Most is just that---dirt, along with old oxidation. I don't use a slotted spoon, just a plain spoon to work the crap to an edge to skim off. You need to stir it good with flux to get all the trapped junk to the surface. No need to worry as long as it comes out clean in the end.

[zxcvbob]

I wonder if the "low level radiation shielding" was zinc instead of lead? (zinc should be good enough to stop alpha or beta particles; not sure about low-energy x-rays)

[Woodsroad]

It's an awful lot of dross. It keeps forming and it's heavy. I'll try using a regular spoon to scoop it out and see what happens...

[Woodsroad]

I wonder if the "low level radiation shielding" was zinc instead of lead? (zinc should be good enough to stop alpha or beta particles; not sure about low-energy x-rays)

It was too soft to be Zn. An alloy, perhaps....but it was soft.

[zxcvbob]

Good. Try fluxing with a little Crisco or lard at high temperature. It will turn some of that heavy dust back into lead. Don't know what to tell you about the glowing smoky stuff.

[Woodsroad]

Good. Try fluxing with a little Crisco or lard at high temperature. It will turn some of that heavy dust back into lead. Don't know what to tell you about the glowing smoky stuff.

OK, I'll try lard or Crisco. Isn't Crisco hydrogenated canola oil? I also have a lot of beeswax (I keep bees, too). What will Crisco do that borax or beeswax will not?

The bloom of dross started after the last flux with borax, I was stirring it in really well, scraping the bottom of the pot as I stirred. I had skimmed off all the usual dross, the top was nice and shiny, I turn back to the kettle and there is this stuff, rising up and accumulating.....giving off a yellow smoke as I skimmed it. Strange brew, indeed.

[odoh]

I read w/interest your comments re the very fine heavy dirt. I too have been experiencing same stuff w/lead pipe/roofing jacks etc. Not so much w/WWs but some. The stuff sticks on the sides, bottom of the pot and even the dipper. Haven't seen it mentioned before now ~ but then I'm new to this.

As for the wierd stuff, I'd treat it like I treat the fine dirt and other dross. Save it and then re-smelt it later to extract what lead I can get out of it before dumping the dirt. I have had good result using pat martins sawdust/shavings. Today, for the first time I used some old borax found when cleaning up the garage to resmelt the save dross w/good results. Keep us posted how it goes ~

[zxcvbob]

I haven't tried beeswax cuz I don't have any bees, so I can't compare it.

Shortening or fat is the best thing I've found for fluxing. Not sure why, but I think it's because the glycerin takes a while to burn off after the fatty-acids are gone -- so after the initial smoke and/or flame, there's a bubbling charred liquid left that's easy to skim (or stir down and let it burn some more.) Old motor oil or paraffin candle stubs burn up too quickly.

[Woodsroad]

I read w/interest your comments re the very fine heavy dirt. I too have been experiencing same stuff w/lead pipe/roofing jacks etc. ...Keep us posted how it goes ~

Yeah, this was roof flashing, Pb pipe, cable jacketing, foundry ingots without any numbers (seemed soft), radiation shielding and sheet lead of unknown origin, all soft.

I smelt in a 20 qt dutch oven, and I guess that it was a little more than half full of melt. From that, I filled a 2 gallon pail 3/4 full with dross.

I'll give it a remelt on Monday and keep the heat lower. Maybe make some pics, too.

[Woodsroad]

...Shortening or fat is the best thing I've found for fluxing. .

Well, we have a tub of it aging in the back of the fridge, I'll give it a try and report back! Thanks.

[Crass Whackwords]

It has been my experience that the drive-you-crazy oxidation is normal with pure lead and or nearly pure lead.

I thought maybe it was some kind of contamination so I bought some foundry grade pure lead and it drosses like crazy, too.

Normally I prefer to cast with a ladle but for these drossy alloys a decent bottom pour pot would be the way to go. Put sawdust/charcoal/what-have-you on top to minimize the dross and cover the pot. Let it dross and don't worry about it because the dross is on top.

If you cast with a ladle, the dross keeps plugging up the ladle and results in lots of cussing. Then you have to flux frequently which smokes and smells and results in more cussing.:(

If you are casting for blackpowder, I guess you have to deal with this dross problem, but for smokeless loads use clip-on wheelweight and life is so much easier.:Fire:

[Woodsroad]

I've been told that I was running the melt too hot. Keep it around 650º. I always watch the temp when smelting WW, but I figured, what the hell, there's no zinc in this stuff, no need to watch the temp to closely...well it seems that pure lead forms lead oxide at higher temps. I have some alchemy experimenting to do now to see if the dross will return to solution. I think not. lesson learned....

[docone31]

I collect my dross. After I have done my prime smelting, I save the dross for the last pot of melt. I toss it in with lots of charcoal. In time, the charcoal breaks down, and so does the dross. Most goes back in the melt.
When I melt clips off, or batch my melt, I do not keep scrapeing the dross out. If I did that, I would have nothing but oxides.
If you leave some on the top, nothing takes its place.

[Woodsroad]

OK, I will try the charcoal route.

Understand, I am not talking about a little dross. I'm talking about 2" of dross.

[Crass Whackwords]

2" ??? Wow, that is a lot. I'm used to seeing 1/4" with pure lead, and 1/4" is bad enough.

Are you saying that after you clean off the 2" of dross, another 2" soon appears ?

Post a picture if you can.

Normally sheathing and flashing is lead with a wee bit of antimony, similar to stick-on WW, but there are other possible additives that are not bullet-casting friendly.

[Tom Herman]

I wonder if the "low level radiation shielding" was zinc instead of lead? (zinc should be good enough to stop alpha or beta particles; not sure about low-energy x-rays)

You need elements a lot heavier than Zink to make effective shielding against gamma radiation. Zink is only atomic number 30... You need to be much higher (like Bismuth at 83) to be effective at stopping gammas...
Yes, almost anything will stop alphas or betas. Alphas are essentially a Helium nucleus, and are stopped by thin barriers such as a piece of paper or two.
Betas are free electrons and are stopped by slightly thicker material, such as a layer of skin (beta burns), or fairly thin, heavy metal.
Gamma particles or energy fragments penetrate deeply, but fortunately don't have much energy. It take a lot of material (the denser the better) to stop it, the higher Z materials work best.

Happy Shootin'! -Tom

[runfiverun]

i am thinking that bismuth might be your culprit here.
you might want to try adding a bit of tin to your melt and see if that helps.
just a small batch and 50-1 might help.

[powderburnerr]

I make 16 pound ingots when i do soft lead and it sets outside til I use it . when I melt it back down I ocassionally get a clump of the stuff in one of the ingots ,I do not see it when I pour them but find them on the remelt . It doesnt seem to effect aanything I just scoop it out when it floats up .and it seems to disolve when i resmelt ..might just be some lead or oxides of lead that is not fully breaking away from the melted lead would be my guess..........Dean

[stocker]

How big is that "large" Dutch oven? ie: what is the diameter? I'm wondering if you have so much surface heat loss that you are getting a large slush layer and the normal dross is bound in it. If so the answer might be more heat or a narrower pot to reduce top surface area.

[Woodsroad]

How big is that "large" Dutch oven?.

It's a 20 qt (http://www.amazon.com/Bayou-Classic-7420-20-Quart-Perforated/dp/B00062WTOW/ref=sr_1_11?ie=UTF8&s=home-garden&qid=1237765863&sr=8-11), fired by the Bayou Classic SP10 burner (http://www.amazon.com/Bayou-Classic-SP10-High-Pressure-Outdoor/dp/B000291GBQ/ref=pd_bbs_sr_1?ie=UTF8&s=home-garden&qid=1237765828&sr=8-1) I keep the lid on as much as possible, but, yes, I think that you may be right about the lead getting bound up in the slush.

I am going to reheat the pot, skim the remaining dross, flux again, then cast ingots. I will then attempt to remelt dross, in smaller quantities, using charcoal in the mix , keep it covered and see what happens. The lead should drop out!

I'll make pix and post them.

Good thinking about thew slush layer, although the pot did hit 780ºf (ouch), it is a possibility.

[Woodsroad]

i am thinking that bismuth might be your culprit here.
you might want to try adding a bit of tin to your melt and see if that helps.
just a small batch and 50-1 might help.

Bismuth, eh?
I think that I'm going to pass some of this dross on to a friend who cna get it assayed at his work....

[Woodsroad]

The assay results are in.

33% by weight Cadmium.

I am fairly certain that the cadmium came to me in the form of octagonal ingots with "SJ" on them. They must have been pure cadmium. I will make some photos and do a more complete write up as time permits.

We all need to be vigilant about cadmium. It looks and feels like lead. It is deadly when inhaled during smelting. Death can occur within 72 hours, with complete renal shut down and cardiopulmonary edema.

Thank God I donned protective gear once the stuff started to look out of the ordinary. ALWAYS keep a high quality respirator with p100 filters handy. ALWAYS use gloves when handling metals. ALWAYS be vigilant of the slightest deviations from the norm in the appearance of your smelting pot. I did, and it saved my life.

[briang]

Wow, that's scary. Thanks for the heads up.

[odoh]

Death in 72 hrs might have been inviting for the victims of Itai, Itai (Japanese word Ouch, Ouch) disease from drinking cadmium contaminated water downstream from a factory in the 1960's. The cadmium would deteriate their bones allowing them to break easily. Its victims shrunk 10" or more as result a slow agonizing death. The factory prevailed in that court case. I recall the newscast that showed an elderly lady that shranked so much she could almost fit in a suitcase. Thanks for sharing.

ON EDIT: After posting this, I googled and surprisingly Wikipedia Free dictionary did list it and said the victims prevailed. My translator had said otherwise at the time ~ donno, maybe on appeal.

[Woodsroad]

It appears that if you do not show symptoms within 48 hours, then toxicity levels are below threshold. The Japanese victims (and employees of smelting operations) were exposed to moderately excessive levels over a long period of time: chronic exposure.

I can only hope that I escaped this unscathed. My lab training stood me in good stead.

Time will tell.

[runfiverun]

cadmium..wow.
i would like to see the ingots.
might help someone from making a terrible mistake.

[Woodsroad]

The ingots were melted, and I never mad pix of them. They were octagonal, with "SJ" on them. But that doesn't really matter. Cadmium will be encountered in many forms, all of which look like lead.

[Slow Elk 45/70]

WoodRoad, thanks for the heads up, these are some of the best reasons for posting unusual situations encountered while smelting/casting.

Thanks again, It sounds like you saved your own bacon when you used the safety precautions you employed. Good for you. This is a good example for all of us to pay attention to what is going on when we are smelting.

[xsquidgator]

Did these ingots come from a radiation therapy department? (I work in one). Until recently we kept hundreds of pounds of "Lipowitz's metal" on hand for making blocks out of this alloy, it melts at 190F. I'd forgotten about it, I knew not to try to use it for boolit making but I'd forgotten about the Cd in it and didn't know or remember Cadmium being deadly.

If you do have some silvery looking ingots that might be this stuff, an ordinary electronics soldering iron will melt into it pretty easily since it melts at 190F. The good news is that in the U.S. anyway, the hand-made block technology is being phased out for something else. We used the low-melting point alloy to make custom blocks for shaping x-ray beams used to treat cancers. Each patient would normally have a set of 2-6 of these blocks made just for him/her and then we'd melt 'em down again after the treatments were complete. We still make blocks occasionally but we have some computer-controlled devices on the linear accelerator x-ray machines that have replaced 95% of the blocks that we used to make. So, at least it is less likely that you will encounter this Lipowitz's metal if you take waste lead and lead-like material from a radiation therapy or radiology department. Radiation oncology --> make sure it's not this special metal, if you're getting the waste stuff from Radiology you don't need to worry, because radiology doesn't use this stuff.

[SciFiJim]

Wow, what a heads up. Scary stuff. I think I'll stick with wheel weights. Mystery metal is something to be careful of. Is there a way to determine the presence of cadmium with out an assay or spectroanalysis?

[303Guy]

If I may ask, where is the flame being applied? I got the impression that the flame was being directed directly onto the melt?

[Woodsroad]

Did these ingots come from a radiation therapy department?

I do not know what the origin was. I bought them as scrap from a recycler...

[Woodsroad]

Wow, what a heads up. Scary stuff. I think I'll stick with wheel weights. Mystery metal is something to be careful of. Is there a way to determine the presence of cadmium with out an assay or spectroanalysis?

Well, it is less dense. Not a lot, but....so you could check volume vs weight.

[Woodsroad]

If I may ask, where is the flame being applied? I got the impression that the flame was being directed directly onto the melt?

Just like anyone else smelts. The metal in the cast iron kettle, the burner is under the kettle.

[Woodsroad]

FOLLOW-UP:

I was able to return the Cd/Pb melt and dross to the recycler and get my $ back. I had my blood levels checked for Pb and Cd and they were below threshold.

If you come across sheet "lead" that seems a just little less flexible and just a tad lighter than it should be, then be warned, it could be cadmium. I related this whole story to my recycler guy and he now intends to shoot any lead that comes in with the assay gun. Cd is a bit valuable than lead, it turns out.

[sargenv]

I was just out melting bullet lead excavated from the backstop at my range and encountered a small amount of yellow smoke.. like just the size of a bullet maybe.. There were some traces of clay targets (pigeons) in the mix of stuff that I tried to get out before things melted, but just could not get to. I had the forethought today to have a fan blowing moderately strong across the pot to keep the smoke out of my face and all of the smoke went off in another direction.. When I saw yellow smoke, I stayed well away from it and now I'm wondering if it was sulfer or cadmium.. it poofed up one more time, and there appeared to be this black, tarry substance that burned off on the side of the pot.. I'm still thinking sulfer compound, thoughts? (didn't mean to hijack the thread, just seemed like it had come to an end and I thought this might be somewhat related). The final lead after I'd skimmed the bullet jackets and dust came out nice and clean with no smoke evident..

[Woodsroad]

Asphalt from the clay birds, or other **** in the dirt. Highly unlikely to be Cd.

[lwknight]

Yup, backstop ore can be nasty for sure. My club range uses some plastic cardboard kin sheets for target boards. Thats really nasty to process.

[Woodsroad]

Yeah, it's some other ****, other than Cd.
Doesn't mean that it will not kill you, it will just kill you differently.

[Woodsroad]

"Krap", does that make it past the filter?

[sargenv]

Doesn't mean that it will not kill you, it will just kill you differently.

Hmm.. like too many pepperoni pizzas and beer eh? ;)

Thanks for the reply all :)

and yes, the "K" word seems to get past the filter...

[sagacious]

The local department store was selling fishing weights labelled as "cadmium." I bought some just to see if it could actually be true. They were slinky weights for steelhead drift fishing, filled-- sure enough-- with cadmium shot.

It's too bad that cadmium is so toxic. It has a low melting point and remarkable cavity fill-out properties. I remember seeing castings of large tropical horned beetles poured from solid cadmium. The beetles were placed in a plaster/bentonite clay mixture, and the mold was heated to orange hot in a furnace. The beetle would burn to carbon, and the solid carbon would vaporize as CO2, leaving a beetle-shaped cavity. Then cadmium was poured in, and once cooled, the mold placed in water which softened/dissolved the plaster. And presto, a shiny cadmium rhinoceros beetle-- every leg, horn, spine, and antenna reproduced perfectly in metal.

There are several metals that would be immensely useful for casting bullets, were they inexpensively available and not so toxic. We have much to be thankful for that lead is easy to use, inexpensive, and not too toxic to work safely with.

[pjh421]

So when I handle cadmium plated parts at work am I killing myself?

Paul

[sagacious]

So when I handle cadmium plated parts at work am I killing myself?

Paul

No.

Just don't eat them, or roast anything over them.

[SciFiJim]

Or melt them.

[lwknight]

And presto, a shiny cadmium rhinoceros beetle-- every leg, horn, spine, and antenna reproduced perfectly in metal.

I always wondered how they did that. It would in effect be making a fossil.

[StanDahl]

I flux again and begin seeing a pretty weird thing: Brown/red/green dross "bloom" starts rising out of the melt. I remove it. It is very heavy, with a consistency of dirt. ...As I remove it, more rises to the surface. It's looks like that this is an oxide, forming as the surface of the melt is exposed. I realize that I could sit there and remove it all day. It looks like rusty dirt, but is not magnetic. If I scoop some up with a strainer, as the molten lead drips out of it, it leaves a
stalactite of slag, which begins to glow and burn off, giving off a thick yellow smoke. I do have a respirator on.


I had exactly same thing happen 10 years ago with some lead I got from a scrap yard. My dross looked like the crust on a peach cobbler, and it just kept coming up. I'd scrape it off, and it would return, then harden to where I had to break the crust to get it out. I got a sick feeling in my stomach when I posted this on the Shooters forum and someone suggested cadmium contamination. I wasn't wearing a respirator. I had all kind of hypochondria about it for a few weeks. I've survived this far, and if it kills me someday, I'll probably have forgotten what could have been the cause.

[Woodsroad]

Stan, you can get a Cd level blood test. Just ask your physician. Or not, if you ever intend to buy life insurance.

For the record (don't remember if I posted this or not) I did get my blood checked, and it is below threshold for Pb and Cd.

Whew.....

[leadman]

Cadmium is used as a plating on most of the bolts that hold the things in our lives together. As a mechanic I used a torch to cut many of these and saw the yellow smoke and thought nothing of it.

Also recently some childrens' jewelry imported from China was found to contain high levels of this metal. Must be because it casts so easily?

[Woodsroad]

Cadmium is used as a plating...<snip>...recently some childrens' jewelry imported from China was found to contain high levels of this metal. Must be because it casts so easily?

That and they don't give a rodent's posterior about the lives of their workers or anyone else in the world.

[sagacious]

As long as one doesn't eat, breathe, etc, the cadmium, it's not going to hurt anyone. Same as lead, which we've learned to handle safely and properly.

Cadmium was used to plate refrigerator racks, as it offers excellent corrosion resistance for that application. However, some folks would use old fridge racks as makeshift campfire grilling racks, and that's apparently a good way to introduce dangerous levels of cadmium into one's diet.

To my knowledge, cadmium is no longer used to plate fridge racks or anything else that comes into direct contact with food-- but just to be safe, it might be best to avoid grilling with fridge racks.