Formulating a porcelain body is straightforward, but does involve a lot of work and testing. Porcelains make a lot of hard tradeoffs (color, translucency, plasticity, glaze fit, cost) so if commercial porcelain bodies don't meet your needs it may be a good idea to mix your own.
The basic idea is simple:
See Formulating a Porcelain on Digital Fire for a broad overview.
There are three attractive properties of porcelain and they are all in conflict with each other:
The whitest materials are hard to mold and throw on the wheel and are expensive. The most plastic clays are contaminated with iron, but cheap.
There is another axis, which is firing temperature. Firing hotter relaxes these constraints somewhat as feldspar can be replaced with kaolin, increasing workability.
This is a good starting point for a cone 10 porcelain.
| Material | Percentage |
|---|---|
| Kaolin | 50 |
| Silica | 25 |
| Feldspar | 25 |
Derek Au tested various kaolins and clays with this recipe.
Tony Hansen has done a lot of research in this area and used it to make Polar Ice at Plainsman Clay.
Here is his recipe for L3778D, a mid range translucent throwing porcelain.
| Material | Percentage |
|---|---|
| Grolleg Kaolin | 52 |
| Silica | 25 |
| Nepheline Syenite | 20 |
| VeeGum T | 3 |
Tony Hansen's soft paste (using frit, powdered glass) porcelain, named Zero4. It is translucent at cone 04. With the use of glass, this recipe shows that translucent porcelains can be fired to very low temperatures. Honestly at this point it feels like you're just making glassware with kaolin dissolved in it.
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