Fluxing questions about smelting and melting

[NoZombies]

I've never been too serious about bullet casting, but have started getting a little more serious lately...

I believe most folks flux with candle wax, wood shavings, or something similar for the melt, but as far as smelting goes, would it be better to flux with a borax based flux?

I have two distinct sources of materials; Wheel weights, which obviously would be pretty dirty stuff, and I also have pure lead, which is pretty clean stuff.

I'm thinking, maybe use the borax based flux (probably a boric acid based flux really) when smelting the wheel weights to rid it of more of the impurities, and use wax/shavings with the pure lead? (I will have to smelt the pure lead as it's large enough pieces that it wont fit into my melting pot.)

Prior to now I've just been melting and ladling the pure lead for round balls for BP, but I picked up a cheap lee bottom pour melting pot, and plan to start casting some boolits.

What do you guys think?

[monadnock#5]

First off, never smelt anything in your bottom pour, as it will cause you agony and frustration long after you've moved on to the better way. The better way is a dedicated smelting setup: Harbor Freight propane fish fryer; plumbers furnace; electric hot plate.... I'll let your wallet make the final decision. I much prefer a stainless steel pot over cast iron, but many members use cast with no complaint.

Borax, I don't know, as I've never used it. Candle wax, remnants of boolit lube, canning paraffin, those are what work best for me. Grated Ivory Soap (stearic acid) also works well but the fumes are offensive.

The idea here is to scrupulously clean the melt at the smelting stage. If well done you don't have to worry about it when casting. I routinely cover the melt with wood ash or wood shavings while bottom pouring. I dump the remnants at the beginning of a session, get the pot up to temp, scrape down the sides, bottom and plug, flux, cover the melt and cast 'til I'm done. If I don't see the dross, I can't worry about it. Inclusions in the melt will leave a tiny, telltale tuft of dross on top of the sprue as it solidifies. Sorta like a cherry on top of a sundae. No tuft, no worries.

[NoZombies]

Very Cool, thanks for the advice!

I was planning to smelt and melt in separate pots... I've got several options for heating the smelt, so there should be no problems there...

Your tip about the dross above the sprue is golden, Thanks a bunch!

[JSnover]

A pretty good post by Linstrum on another thread:

"A couple of things about re-claiming scrap lead alloy like wheel weights:

The main thing about using a reducing-type cleaning agent like wax, sawdust, etc, is to RECOVER the oxidized minor alloying constituents in with the lead. Lead metal is a bit more inert than tin and antimony, and due mostly to what is called the Electromotive Series of the Elements, when they are in contact with lead, the tin and antimony will for the greater part oxidize before the lead does because they are more reactive. In essence, if a bit of lead oxidizes, the lead oxide is immediately attacked by the elemental tin and antimony and the tin and antimony accept the oxygen from the lead oxide to reduce it back to the elemental lead form, and in doing so the tin and antimony become oxidized and stay oxidized. On top of that, tin and antimony quite readily oxidize when hot and in contact with the oxygen in the air. If a FLUX is used at this point it will REMOVE the tin oxide and antimony oxide floating on top of the alloy in the melting pot and deplete the alloy. To prevent depleting the desirable tin and antimony alloying constituents, a REDUCING AGENT is used, like wax, sawdust, sugar, polyethylene plastic sandwich baggies, powdered charcoal, straight non-detergent motor oil, vegetable oil, etc. The reducing agent will attack the tin oxide and antimony oxide and reduce them back to their elemental forms by removing the oxygen combined with them, and they will immediately dissolve back into the alloy where they belong. This is a good thing because it keeps from depleting them in your alloy.

The best material for treating scrap lead alloy is pine tree pitch (rosin) since it has both reducing agent (smelting) properties as well as fluxing properties and it will readily reduce the tin oxide and antimony oxide back to their elemental forms plus remove unwanted dirt without removing the tin and antimony, unlike a straight fluxing agent such as MOLTEN borax. But if you don't have access to a pine forest to get pitch for free don't worry about it, just use sawdust, wax, or whatever, since they work pretty darned good, too. By the way, don't bother using borax for boolit casting alloys, the melting pot temperature is way, way too low for it to work since it must be molten at a bright red heat to have an adequate effect.

A magnet is a pretty good idea to get the clips and other iron debris out. If you have a rare earth magnet like a cobalt-samarium magnet, it might be a good idea to stick it onto an iron spatula where it won't get too hot since high heat could possibly degrade the magnetic strength after awhile and those super-powerful magnets are pretty expensive. I have one I use to trick kids with, I hold it clenched in my fist out of sight and pick up nails on my knuckles.

Like Bret4227 already mentioned, pure lead metal has to be pretty darned hot to generate any lead vapor, which is why boolit casting is a pretty safe activity as far as breathing poisonous lead fumes. But - what will get you is the antimony oxide dust that is always around in small amounts no matter what you do to keep it reduced back into the alloy like I just said above. For those of you who have not had chemistry, antimony is right below arsenic in the Group 15 elements (nitrogen, phosphorus, arsenic, antimony, and bismuth) and resembles arsenic a great deal in its chemical properties, including being darned poisonous in rather tiny amounts! So, be careful about breathing or otherwise accidentally ingesting any dust from the dross.

Have fun!

rl537"

[Duckiller]

If you have real oily or greasy wheel weights DON'T clean them. Used oil is a great flux. Aslo stir with a wooden stick another great flux. I used to create all sorts of smoke and fire when fluxing with wax etc. Now I just dirt on weights and a stick. Melt the weights and fish out the clips. Stir with the stick to make sure nothing is hideing deep in the pot then carefully remove dirt and other bad things floating on the surface. Over time I have come to the conclusion that keeping the melt temperature low helps produce clean ingots. I turn the burner up high to get the lead melted, but before I start removing clips I turn the burner down low, hot enough to keep the lead liquid but not roaring flame.

[NoZombies]

Okay, Cool, so to overview:

Borax based fluxes aren't generally recommended, but rather a reducing flux to help maintain alloy percentages in the scrap.

Pine pitch or similar is a good idea for a flux. (conveniently I have a stash of fat lighter wood.)

And turn the heat down before removing dross and crap...

Well, that's all good news, I'm not a fan of barax/borric acid fluxes when they can be avoided... nasty stuff to ingest or inhale.

I will be wearing a respirator, I've had heavy metal poisoning before, and I'm very sensitive to even small doses of air-born particulates.

Thanks for all the info guys! anything else I'm obviously missing?

[cuzinbruce]

Fluxing with caustic? I have a copy of Magma's bullet casting book and he discusses fluxing with caustic to clean the metal. I don't have the book in front of me, but IIRC he was using sodium hydroxide. Anyone here have any experience with that? After the caustic, he fluxed again with something else to remove any of the caustic remaining.
There are so many warnings associated with sodium hydroxide that I have always avoided using it in other areas.