Premium Clay (also goes by the name Builders Clay or Ball Clay) consists of super fine kaolin clay and has high dry strength, refractory and plasticity properties. Premium clay should be used with caution as it can cause the structure to be weaker then intended or shrink. There are a few things to be wary of like the type of sand being used and the amount. The rule of thumb is use as little as possible. The main issues for the product is plasticiser for building mortar, general purpose filler or an ingredient in refractory formulations.