Q: I've gotten curious about Faience, and I want to try it out. Do I need a special kiln? What is it best for, and what special treatment do I give it?
A: Faience, or Egyptian paste, was the stuff the Egyptians used to make some of their small statuary and jewelry items, most famously a hippo in the collection of New York's Metropolitan Museum. The clay object makes its own glaze as it dries, by sodium compounds that were mixed into the clay body migrating to the surface and crystalizing there . A turquoise color based on copper oxide and soda ash is the most common, but other oxides and soluble sodium compounds may be used for diferent effects.
Just about any kiln should work. This is a low-temperature process; in the (cone 08) earthenware , not the stoneware range. It is best for small items; it lacks the structural strength to make big ones., but it is easily press-molded or impressed with stamps. The clay has little plasticity, so compact objects work best. Handle the dried objects very carefully, if you must, so as not to dislodge the crusty stuff that covers them, because that's the glaze layer, and it's extremely fragile- if a chunk falls off you're left with a bare spot on the piece.
It's probably best to let a few pieces dry on a kiln shelf, so they can be loaded into the kiln without picking them up individually. The shelf should be heavily kiln-washed, and/or stilts can be used. If you're making beads, they should be strung on nichrome wire and put in position on the firing rack when wet, for the same reason. Daniel Rhodes, in his classic Clay and Glazes for the Potter (c.1957 Chilton Company NY LCCCN 57-11905) gives the following "typical formula" :
ball clay 5
Sodium Bicarbonate 6
Soda ash 6
Fine white sand 8
He recommends adding bentonite or dextrine to counteract the shortness of the clay, but doesn't specify the proportion of copper. Offhand, I'd say 1 part of copper oxide or 2 parts of copper carbonate should do it, but this formula is obviously meant as a base for experimentation. Let me know what works for you.
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