All Glossary

Casting Slip

To make casting slip you need to understand deflocculation and have a good propeller mixer. If you are already buying a premixed powder then shifting toward your own recipe will be much easier. Making your own affords flexibility. Commercial stoneware or porcelain casting slips will almost certainly have a recipe similar to that discussed on this page.

Porcelains and white or buff stonewares

Kaolin: Most kaolins are non-plastic and so are a natural fit for use in a casting body. White-burning ones are more expensive. Availability and price will likely determine which you use.
Ball clay: All ball clays are highly plastic and thus not good for casting. A few larger particle size ones are available and producers target them to casting. Use one of those. White-burning ones are generally less plastic, thus more suitable.
Feldspar: Likely you don't have many available, try the ones you can get.
Silica: This should be available everywhere and it fires white, use a 200 mesh version.
Bentonite: At most, only 1% is likely needed. Get one that is processed to at least 200 mesh.

L4807 Recipe for Cone 6 (using the most suitable materials in the US)

OptiKast Kaolin 30
Silica 25
KT #1-4 Ball Clay 20
Nepheline Syenite 25
Talc 0.5

Tuning:

Increase ball clay at the expense of kaolin for better green strength, better mold release (but slower casting).
Add bentonite for better mold release (it increases drying shrinkage).
Increase Nepheline at the expense of clay for more fired maturity. If feldspar must be used the body will be less mature so more will be needed.
Glazes should not craze with 25% silica and if the body is mature, if they do then fix them (by lowering their thermal expansion). Glazes may fit with 20% silica, or even 15%, if so then increase feldspar if more maturity is needed, otherwise kaolin.
Add talc for better maturity (up to 2%, otherwise increase nepheline).

Terra Cotta

Coming.

Black cone 6 Stoneware

Coming.

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