This is an unusual cone 10R vitreous sculpture clay (code number L3118J). The grogless base burns dark brown and is almost porcelain-vitreous. All of the surface variegation is a product of the contrasting colour of the dark brown body and lighter coloured grog. Almost all of the fired porosity is from the refractory grog particles.
This was inspired by Craft Crank, a UK-made highly grogged body: A super-plastic base that can host a high percentage of coarse grog particles yet still offer very good workability (and be throwable, even non-abrasive, on the wheel). My base has 40% ball clay, 10% plastic kaolin, 20% Redart, 5% quartz and 25% 20x48 grog. Redart is an illitic clay, containing K2O like a feldspar, the 20% here has enough fluxing power to vitrify the body. Given recent changes in Redart, this recipe could be modified to compensate (e.g. add iron oxide, use 45 ball clay instead of a 50 ball clay/kaolin mix, add 5% feldspar).

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This cone 10R piece is about 8 inches tall and quite thin-walled. This is L3118J grogged clay with 25% Christy Minerals STKO22S grog. It is not a typical grog having a range of particle sizes, these particles are all close to 20 mesh. Because the base body, mainly Redart and Ball clay, is so fine and plastic, and the grog is only one size, this is not only throwable but resistant enough to splitting that large pieces can be made. The plasticity of the base and the mobility of the grog particles within enables applying pressure with surprisingly less abrasion than expected. And of course, the grog makes it highly resistant to cracking during drying.
| Materials |
Grog
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| Materials |
Redart
The most common commercially 200 mesh available raw terra cotta clay in North America. It fires red, has low plasticity and matures a low kiln temperatures. |
| Glossary |
Sculpture
In ceramics, clays with added aggregate are free formed or molding into shapes that are slowly dried and fired in a kiln. The process requires much skill. |
| Glossary |
Grog
Grog is a term used in ceramics to describe crushed brick (or other fired ceramic) aggregate that is added to sculpture and structural clays to improve drying properties. |
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