Fluxing Tin

[Chris C]

Does one flux Tin the same way one fluxes lead...........and with the same material?

[JSnover]

Yep. Treat it the same as lead, you'll be fine.
http://www.lasc.us/Fryxell_Book_Chapter_4_Fluxing.htm

Here is what you want to know, from the bottom of Glens page:

"Is there anything that combines these two modes of operation so that we can get all three of the desired attributes? Fortunately, there is. What’s more, you probably already have a pile of it in your shop. It’s good ol’ fashioned sawdust (hold the motor oil, thank you). The benefits of sawdust are that it‘s a sacrificial reductant that can reduce any oxidized tin back to the metallic state, and it‘s cheap enough that the caster can use enough to form an effective barrier layer to protect the alloy from subsequent oxidation. What’s more, as the sawdust chars on top of the melt, it forms activated carbon, which is a high surface area, porous sorbent material that has a large number of binding sites capable of binding Lewis acid cations like Ca, Zn and Al. So it not only keeps the tin reduced and in solution, but it effectively scavenges those impurities that raise the surface tension and viscosity of the alloy (Al, Zn and Ca), keeping the alloy in top shape for making good bullets. Vigorously stirring in a heaping tablespoon of sawdust into a pot full of bullet metal does a fine job of conditioning and protecting that alloy. Sawdust doesn’t really qualify under the formal definition of “flux” as it doesn’t produce a fusible slag, but it does very cheaply and very effectively accomplish the three primary goals that we set out for cleaning up bullet metal. Reduce, remove and protect, sawdust does it all!"

[Chris C]

Being a retired professional woodworker, I not only have a lifetime supply of sawdust...............but still have all the equipment I need to make 500 lifetime supplies. But my question was specifically for Tin..........or in this case, Pewter. I'm melting down all the Pewter I've accumulated and want to make sure any impurities end up in the trash. So do I just use sawdust in the same way I would with lead?

[Yodogsandman]

Yes, flux 3X with sawdust to clean. Melt any questionable "pewter" pieces separately from hallmarked pewter and keep the temperature down below about 500*F.

[JSnover]

"The benefits of sawdust are that it‘s a sacrificial reductant that can reduce any oxidized tin back to the metallic state"

It works the same way whether your pot is filled with pewter, tin, lead, lead/tin alloy.

[Chris C]

Okay, guys, thanks.

[bangerjim]

WATCH YOUR MELT TEMP!!!! Sn melts at a much lower temp (450F) than Pb (622F). The hotter you get it, the more SnO2 you form. You need to flux but do not use near the temps you would to melt COWWs and Pb and you will have very little oxides.

The reason we get oxides in casting pots is because we have to run the alloys and ~750 to cast and the Sn oxidizes rapidly. That is why we use beeswax (only) to REDUCE in a casting pot.

[runfiverun]

to reduce the oxides back in.
fluxing is something else.

[Chris C]

I know to keep the temp around 450*..........that's what I did when I previously rendered it. Last time I was able to render it in my casting pot with the PID. This time I've got close to 30#, so will need to use my big pot on the turkey fryer. I'll just have to keep the flame down and go slow............turn the heat back a little bit when the Pewter finally starts to melt.