This is a sculpture body named Industrial Crank from Potclays in the UK. I dried some out, slurried and screened the grog out then dewatered the remaining clay to get this. There is almost 50% grog. Yet this body is known for amazing plasticity and toughness. How is that possible with this much grog? That base clay. It is extremely sticky and plastic. Yet it has only 6% drying shrinkage. The grog has a narrow range of sizes, from about 35 mesh to 70 mesh (a high percentage is of the coarsest size). Yet amazingly, the body does not feel coarse. Why? Again, it is this clay base. Each grog particle is nestled in a buffer that firmly holds it yet gives it freedom to move. I am working on a complete report and will share from my Insight-live.com account soon.
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.
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.
Drying Ceramics Without Cracks
Anything ceramic ware can be dried if it is done slowly and evenly enough. To dry faster optimize the body recipe, ware cross section, drying process and develop a good test to rate drying performance.
Clay Cracking During Drying
The best way to avoid drying cracks when making ceramics or pottery is to avoid doing the things that cause it. Do not just blame the clay, anything can technically be dried.