This mug was made using the process of slip casting. Slip is liquid clay used in the manufacture of ceramics. Slip casting involves forming ceramics using slip and a porous mold, usually made of plaster of Paris. Slip is poured into the mold and allowed to set as it coats the walls of the mold. The excess is then poured out, leaving a thin-walled hollow form. This is allowed to harden, and the mold is removed. The piece can then be fired as usual.