Something floating to top at high temp

[RG1911]

I was creating an alloy with COWW and some other stuff that I knew included linotype. When the mix went past about 740 degrees F according to my lead thermometer, a silverish material started floating to the top and refused to be fluxed back in. (I was using wood shavings.)

I'm *assuming* it was tin (possibly antimony?), but was unaware that it would separate out at a particular temperature.

Thank you for any pointers or information.

Richard

[John Boy]

Flux the melt again and the tin will mix back into the alloy

[runfiverun]

tin turns the top of the alloy gold at about 750-f.
antimony can come out of your alloy and form a lumpy surface, you need to turn the heat up a little higher and flux this back in.
the tin usually responds better to a oxygen free barrier on the surface

[RogerDat]

Is tin on the surface one of those situations where wax works better than wood chips or sawdust?

[RG1911]

tin turns the top of the alloy gold at about 750-f.
antimony can come out of your alloy and form a lumpy surface, you need to turn the heat up a little higher and flux this back in.
the tin usually responds better to a oxygen free barrier on the surface

The surface is lumpy, so I'm thinking it may be antimony.

The temperature did hit about 840. Fluxing with the wood shavings didn't work. Perhaps beeswax might work better?

Thank you,
Richard

[bangerjim]

I always use beeswax in my casting pot. It has a much higher flash point than cheap old candle wax and smells great! I have always found chunks of burned sawdust in my pot when using dust and quit doing that after trying it a few times. Dust is great for your initial melt...flux 3X....and pour your ingots.

Beeswax, for me, is almost like magic.........the scummy, lumpy, chunky Sn/Sb that can form on the surface goes back into the soup with just a little pea-sized piece of the wax and some stirring! Pure magic! Keep your temp down and that will minimize the oxidization.

banger

[Forgetful]

Fluxing should only be done at the right temperature. Not too cold, not too hot. I'll put carbon in before it starts to melt, just to limit oxygen exposure. But the stirring in flux and pouring through your floating flux should be done 700-750F.