Fluxing Question

[fordfan]

When smelting in order to make ingots I understand and do flux with sawdust. In doing this I get pretty clean ingots and my question is, If your ingots are clean is it necessary to flux again while in the casting pot? And if you didn't would it hurt anything or cause problems with the boolits?

[Jeffrey]

I flux only as necessary. If your ingots are clean, and the metal in your casting pot is clean, additional fluxing would only be necessary as the tin gets oxidized. If your casting pot is a bottom pour, you would be far better off using wax (hydrocarbons) to flux as this will keep debris out of the nozzle. Others may be able to better speak on bottom pour pots as I don't use one for casting.

[40Super]

I usually put a small layer of sawdust on top to keep an oxygen barrier. Otherwise I don't really do a fluxing on already clean ingots.

[shadowcaster]

I usually put a small layer of sawdust on top to keep an oxygen barrier. Otherwise I don't really do a fluxing on already clean ingots.

This is what I do as well...

Shad

[Defcon-One]

I only do it in the casting pot to keep the Mix, Mixed!

Like when I add a new ingot or two!

It doesn't take much flux in my 20 pound pot.

[7Acres]

I always keep sawdust on top while I'm pouring cast Boolits to keep anything from oxidizing. Every time I drop in an ingot or two I add a generous pinch.

[leadman]

If your clean ingots spent any time setting around before you use them there will be a layer of oxidized lead on the exterior. How bad depends on time and conditions. So I always flux when adding ingots to my pot.

[geargnasher]

All you really NEED to do for clean, fluxed ingots is reduce the oxides. You can do that with sawdust or wax, your choice. Wax, rosin, animal fat, oils, etc. all make excellent sacrificial reducants, and work especially well if you "light them off" or "light the smoke" to produce carbon monoxide near the alloy's surface.

No harm in using sawdust for a reducant in the casting pot, just don't do anything that will carry ash clear to the bottom and get trapped between the alloy and the bottom of the pot. Scraping the bottom with a wood stick, or poking an ingot into the molten alloy such that it traps and carries ash to the bottom on the end will result in stuff coming out in your boolits as little pits and inclusions.

I like to keep a layer of sawdust on top, and leave the ash alone to seal the surface so I don't have to fool with it until next time I add ingots. I reduce and skim again before adding ingots, and again after they melt.

If the lead has solidified, it has a tin/antimony-rich surface oxide coating. It's immediate, happens even before the metal has frozen, and there's nothing you can do about it short of having your entire casting operation in an oxygen-free environment. Keep this in mind when you toss sprues back into the pot.

Remember too, sacrificial reducants will take care of oxides just fine (as will sawdust), but FLUXING to remove undesireable contaminating metals is the job of a true flux such as sawdust. Sawdust fluxes and reduces, Marvellux fluxes but DOES NOT reduce.

Gear

[leadman]

Gear, I have been having a heck of a time trying to clean the trash out of my alloy since I started using sawdust, wax, etc. I was pushing the sawdust thru the lead and that sounds like a mistake. I had run out of Marvelux at least 6 months ago.
Today I used the Marvelux that I just purchased and the oxides on the top returned to the alloy faster then anything I have used recently. The alloy also cleaned up very nicely after about 5 fluxings. The appearance of the alloy has changed dramatically. I am going to clean my pot and remelt a batch of alloy and flux it with ML before using it again. I have about 1,800 pounds to clean up!
I did notice the new ML I have is much finer grained than what I had before. Could the formula have been changed?

My neighbors also might appreciate the fact that now there will be almost no smoke and no odor from my pot!

This is my experience from earlier today and it may be different from others experience. Now I'm off to the lake for 3 days of fishing and relaxing.

[geargnasher]

WRONG! The Marvellux didn't return the oxides to the alloy at all, they were absorbed into the borate glass and permanently removed.

This is one of the reasons I hate that garbage.

If you insist on using it, at least reduce the surface oxides with paraffin wax or something, light the smoke/fumes, stir the top of the mix, skim the ash quickly, and THEN do the fluxing with the borate.

Gear

[leadman]

I'll have to watch the next time I use it and see if the dross I remove is heavy or light. Would be a good experiment to have 2 samples tested to see if the tin or antimony content changes when using the ML. If the member here runs some more tests maybe I'll do this just to see.

[geargnasher]

Or you could investigate the chemistry and understand what happens that way. Or not.

Gear