Still a bit flummoxed about fluxing.

[Flintlock Hokie]

OK, I've read NUMEROUS posts about fluxing as well as the Fryxell and Applegate article "Fluxing the Melt." I've been using sawdust (by the handful) when smelting wheel weights. In fact, I made a bunch of cupcake ingots then mixed them up and smelted them again just to get my 150 lbs of weights well blended. I've been using a paint stirrer to try to get the sawdust and the metal mixed. I've also been lighting the sawdust after it's smoking lots. I don't have a bottom outlet pot, so I can't leave the sawdust on top of the melt. I have to skim it off.

So what is the melt supposed to look like AFTER smelting? No matter what I do, I still get a very thin layer of light gray material on top of the melt. I assume this is lead oxide. Is this correct? Is this normal? Only rarely has my melt exceeded 700 F. Mostly I've managed to keep it in the mid 600s.

When I cast I flux again, usually with paraffin, though I could use sawdust again. Sawdust is just more of a pain because I don't have much freeboard with 8 lbs of metal in my 10 lb pot.

What's the criteria to flux again?

Are there any pictures or videos out there that show before and after fluxing?

Thanks!

[btroj]

That skin of lead oxide is just going to happen. Hot metal in contact with the atmosphere.

Ignore the skin.

[geargnasher]

I ladle-pour amidst a quarter-inch layer of sawdust just fine. The key is a Rowel ladle. If you ladle, you're exposing much more of the alloy to the air as you work it with the ladle, so the sawdust helps. Messy, but no worry. 1/2" of "freeboard" is all you need.

If you keep a "clean pot", i.e. flux and skim, oxide scum is inevitable. If you've fluxed with sawdust when smelting or at the beginning of the session and haven't added too much "contaminated" alloy, just a pea-sized piece of any kind of wax thrown in and stirred will reduce the scum back in very quickly in the middle of a session. Lighting the fumes helps the reduction process by creating carbon monoxide near the melt's surface.

Gear

[Flintlock Hokie]

Rowell ladle… interesting design; easy to see see why it works. I have a Lyman dipper ladle. It's not the same as a Rowell, but it should keep most of the flux on top.

Thanks

[grouch]

I flux with cooking oil(unsalted). Works for me, but scum does form atop the melt. I flux after melting, then skim the scum when necessary until I'm done with that batch, then remelt the sprues and scum and flux befor turning off the hat.
Grouch

[9.3X62AL]

What Btroj said. I'm a bottom-pour caster, FWIW.

[btroj]

I use a standard ladle for pouring ingots when smelting. I just ignore the film, it goes into the ingots too.
I use a bottom pour pot for casting and I ignore any film there too. I se sawdust to flux my casting pot and just leave some of it on the melt while casting. Or sometimes I skim it off.

This need not be rocket science. Clean the melt when smelting raw materials. Flux again when preparing to cast

[geargnasher]

I flux with cooking oil(unsalted). Works for me, but scum does form atop the melt. I flux after melting, then skim the scum when necessary until I'm done with that batch, then remelt the sprues and scum and flux befor turning off the hat.
Grouch

You aren't "fluxing". All you're doing with the cooking oil is reducing oxides to elements, same with any grease/wax/oil. If you want to "flux", you need to add something that absorbs the impurities from the melt and draws them to the surface where they can be skimmed off.

Gear