/charcoal foundry/ galvanized or ss?

I'd go with the SS. Zinc fume fever is no fun:

Symptoms: flu-like illness with a metallic taste in the mouth, throat irritation, and dry cough;

Signs: leucocytosis (high white blood cell count) is common; normal chest x-ray;

Onset after exposure: 3-10 hours;

Heavy exposure to: zinc oxide fume or dust, e.g., after welding or flame cutting of galvanized steel, high temperature zinc coating processes, or metal pouring in brass foundries; (Brass is an alloy of copper and zinc.)

Resolution: spontaneously within 48 hours;

Comments: After an episode, there is a temporary period of tolerance for a day or two afterwards. Copper and magnesium fume can also cause metal fume fever. It is important to distinguish metal fume fever from cadmium pneumonitis.

Be careful out there, and have fun!

-- Ed Huntress

For the shell of your furnace, galvanized sheet metal is fine. That's all I've ever used. It doesn't get hot enough to worry about zinc fumes. At least, I've never noticed any, and I use a homebuilt (ala Gingery) electric furnace indoors, summer and winter, for melting aluminum ( *not* aluminium, hehehe).

CVC

The straight sided shell will be easier to work with. You'll probably abandon the charcoal furnace pretty soon anyway. Look in the yellow pages for "refractory", that's what you'll need for the lining. Or use the fireclay and sand mix. Fireclay comes from masonry suppliers.

As far as never upgrading to propane, I've built all three types and propane is definitely the best.

Arcady wrote: I know that zinc is bad for home melting - but how

The Zinc is not a problem unless you are going to get it close to red hot.

Try your pottery stores for high temp cement. Sodium silicate all so known as water glass.

You might also think about using vermiculite or perlite as an insulating refractory inside the shell. And some hard refractory for a liner.

Dan

I beg to differ. A couple of decades ago I was boring galvalized castings on a turret lathe and got classic metal fume fever apparently just from the heat of the machining - which was nothing close to red hot. I walked out of the shop in a bit of a daze and when I came back told the foreman I wasn't going to do that particular job anymore. NO fun.

This is not to say that the outside of a well insulated foundry would necessarily get that hot, but why take a chance if there is not compelling reason to use galvanized?

Mickey

Things get pretty hot when machining. If the chips are coming off and turning blue, they are pretty hot. Much hotter than the outside of a furnace ought to get. I would not hesitate to use galvanized steel on the outside of a furnace. But having had fume fever from welding galvanized, I understand how you feel.

Dan