Tapper clay is used to seal the drain hole in melting vessels in the smelting industries. It is refractory, low in potassium and sodium to prevent glass development (and therefore harden the plug excessively), and high in aggregate. The wet pugged clay comes into contact with molten metal, thus it needs to be able to liberate its water quickly without popping. Tapper clays are pugged very stiff to minimize the water content. They can be oil or water based.
Example of a tapper clay fired to cone 8 and 10 oxidation and 10 reduction
Specification for a Tapper Clay lacks physics
Often ceramic clays are described on data sheets primarily by their chemistry (and requested as such). This is typically done at the expense of physical properties data. For example, Tapper clay is employed to plug the drain hole of ladles used to melt metals in the smelting industry. The operators of that equipment confront, in the physical presence of the material, many properties that have no relation to the chemistry (e.g. plasticity, shrinkage, water content). Notice also that the chemistry is not correct anyway, it species calcined material yet does not total 100. It specifies no carbon, yet this chemistry is like a ball clay, all of which have some carbon.