Fluxing

[870TC]

As a newb I'm reading everything I can about casting, and ran across something dang confusing.
In the Lyman Cast Bullet Handbook 3rd edition, page 43 theres a article by Dennis Marshall "The Metallurgy of Molten Lead Alloys". Under the section titled Metallic solutions, he says" lead/tin/antimony will never seperate while melting at casting temps and that fluxing is only for taking dirt etc out of the melted metal"
I've read in a bunch of other places that the tin seperates and forms a "gray scum" on the top of the liquid lead and to flux to mix the metals.

Then on page 51 under the title fluxing he says to "add enough wax to cover the surface of the liquid metal by a 1/4 inch".
Well holy crap!, most places say use a pea size lump of wax.

Then on Page 57(same dang book) under bullet casting-"melting & fluxing" they say to flux with a pea size of wax and that fluxing is required to recombine the tin that seperates from the lead. Just opposite of what they said a few pages earlier.

So how much flux material and what is the fluxing actually doing?

[bradh]

870TC you read correctly that "at casting temp's lead/tin/antimony will not
seperate". get very hot and they will. I steal candles from the wife to flux.
Just a pea size or smaller is all that is needed. Experimenation will tell you
how much. And yes this method of fluxing is just taking the crap out of the mix.
I use a small spoon to remove the grey crud from the surface....then it's nice
and shiney! Stir the pot while fluxing.

[GabbyM]

One of the things fluxing does is add a carbon atom to bond with and remove an oxygen atom. releasing different oxidized metals back to the more pure state we want.

The average kitchen is chocked full of things you can use for flux. Some smoke more than others. Armour white lard works great. Then Crisco shortening and cooking oils. I keep a dish soap squirt bottle with some peanut oil for fluxing.

With my bottom poor I've been trying Twenty Mule Team Borax sprinkled on top of already fluxed and cleaned alloy then left their. I tried cat litter but couldn't warm up to dirt on my lead. Alloy

When smelting outside and smoke and high flame isn't an issue use lots of flux material. I'll put a whole Tbs of lard in my 5qt pot. Toss in a match. It will light by itself. Then stir away. If the grease doesn't' light or goes out I'll run the spoon over the flame to light the oil on it. I don't' like allowing the fumes to build up since when the go off in a fireball I'll flinch and toss hot lead all over. Not good

[leftiye]

As most fluxes smoke like h@!!, and catch fire if hot enough. Would you rather have enough smoke to be irritating (pea sized amount), or a huge cloud of smoke? A 1/4" layer would be maybe an ounce of waxy smoke. If it ignited it would be a veritable bonfire! The smaller amount will flux just as well. It doesn't smoke as much when it burns, but I don't like fires in my house, nor huge amounts of smoke.

[Calamity Jake]

The crust that forms on top of a freshly fluxed pot of lead/ww is a paper thin layer of tin that has oxided, if left undisturbed it will not get any thicker.
Fluxing returnes that layer back into the mix and removes dirt at the same time. Adding aprox. 1/4 inch layer of anything that does not burn (cat litter, powdered borax, charcoal and a few others and some thing that do burn but leaves a charcoal layer behind) will prevent the tin from oxiding again.

Again the tin will not seperate form the mix, but will oxidize at the surface only.

[dromia]

Ditto Calamity Jake, its oxidised, the tin thats come in contact with air.

I just flux at the start of a session, more out of habit than necessity methinks, with a dry stick. I then scrap the crud to the side of the pot with my spoon and the press it back into the melt between the back of the spoon and the wall of the pot.

All I get left with is some occasional powder that I think is the crushed carbon from the stick, the oxidised tin goes right back into the melt.

[Junior1942]

Fluxing mainly makes the caster think he's doing good by making magic smoke. I haven't fluxed in over 20 years, and it has made zero difference. Long ago I read where the stuff in bullet alloy is in solution like salt is in solution in sea water. Fluxing bullet alloy to keep the metals in solution is like fluxing sea water to keep the salt in solution. But of course there's that magic smoke. . . .

[utk]

It is often said that fluxing removes crap from the melt. But how? What 'mechanism' is involved here?

I have found (with my little experience) that simply stirring the melt will get crud (dirt from the ww's) to rise to the surface. But I think the stirring simply helps the crud to rise. If left undisturbed, the weight of the alloy will keep it pinned down. Those small sand etc. particles simply haven't enough buoyancy to rise by themselves.

Now, does fluxing make this process simpler/better, or what? The reduction of oxides back to metal sounds true, but 'cleaning'?
Is it simply the stirring that brings the crap to the surface and everybody thinks the flux did it?

I think that fluxing reduces the 'gray scum' back to metal. At the same time the stirring brings the dirt to the surface. The caster sees the gray scum disappear and now see dirt particles instead and believes the fluxing 'cleaned' the alloy.

[timkelley]

I'm not sure if I'm doing a lot of good but a stirring stick made out of Pine or Red Fir and couple pinches (sawdust), of the same, in the pot seems to, at least, make Junior's "Magic Smoke".
I get very little residue and the area smells good.

[Southern Son]

I have been using Matthews No. 2 BPCR bullet lube to flux. If the pot is over about 700 degrees, then it will burst into flames al by itself, saving me a match. When it burns there is very little Majic Smoke, but if I throw in the flux before the pot gets up to 700, then there is a spectacular cloud of smoke. If I forget to close the window over the carport where I cast, then I get a revving from my missus.

[Boerrancher]

when I get too much crud on the top of my little Lee production pot I toss in a pinch of pipe tobacco. Out side where I don't care about the smells, I have used every thing from ground corn, or candle wax, to goat dung. Anything that adds carbon to the dross will work well to bring out any impurities and mix back in any tin and antimony that you may have cooked out while smelting your raw WW or range scrap.

Best Wishes from the Boer Ranch,

Joe