Question on fluxing

[grimace1]

As I understand it, carbon is the substance that actually serves as the flux. I work in a carbon black plant. Carbon black is pure powdered carbon made by partially combusting crude oil. I can get all of it I want for free, and I am curious if it would made a suitable fluxing compound. Anyone have suggestions on that?

[shredder]

Tagged for interest!
I am pretty sure it will work but since I have never actually used that substance for flux, I will let someone with direct first hand knowledge answer. If it were me I would already have some floating on the melt!

[Freightman]

don't stand close you will lose your eye brows! Use saw dust safer I know what I am saying been there done that.

[Defcon-One]

I would argue that the process of going from organic material, like sawdust, to charcoal is what does the reducing. I suspect that the wood rosin, etc. from the sawdust does this. The charcoal powder, carbon, on top is the shielding agent that also binds with and carries away the impurities that rise to the top.

Flux:

Reduce Tin, Remove Impurities (clean), Prevent Oxidation (shield)!

That is what I would say!

I'd use pine sawdust! It is cheap and effective and smells good, too.

CD-1

[btroj]

Carbon is what adsorbs the impurities but it doesn't reduce oxides. It is half the equation. It also is fine enough that it might be a pain to skim off the melt.

Sawdust is cheap, easy to get, and it WORKS!

[Bigslug]

All the advice here on sawdusting says to let it burn completely before stirring in, so I tend to doubt that there's much besides straight carbon going in - at least that's serving any useful purpose.

The finer powder MAY increase the effectiveness of the flux by increasing the carbon's surface area. Then again, the porousness of sawdust MAY have something going for it.

But if you are dealing with, as you say, pure carbon, it isn't going to hurt anything to try, and you may discover something useful without loosing a dime. Find some scuzzy wheel weights and do a side-by-side test of sawdust vs. carbon black to see which makes the prettier ingot.

[btroj]

Wrong bigslug.

That burning is important. It is what produces carbon on oxide, the reducing agent we need. It reduces the oxides back into the melt. The carbon then can adsorb the impurities.

Straight carbon doesn't reduce.

[Bigslug]

Hmmmm. . .

From our friends at Wiki: "Carbon black (also known as acetylene black, channel black, furnace black, lamp black or thermal black) is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil.Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio, although its surface-area-to-volume ratio is low compared to that of activated carbon."

I'm interpreting this to mean it's probably not AS effective for our purposes as the more porous sawdust ash (activated carbon), it would still get the job done with greater quantities and patience.

[btroj]

It is an excellent medium for adsorption of Impurities. What it WON'T do is produce carbon monoxide gas. The incomplete combustion of sawdust is what does that. Carbon monoxide is a key player in the reduction of the various oxides that form the scum on the surface of our melt. Things like tin oxide, someone we want reduced back t metallic tin so it stays in the melt rather than being removed.

Carbon black would remove the impurities, it won't reduce anything back into the melt. Sawdust does BOTH.

"Fluxng" in the sense we mean is a two part process, the carbon black only performs one part.

[Buzz64]

OK, so whats wrong with MARVELUX? Seems to do a great job for me and doesn't take much.