Plates include: Numerous 30 mm diameter perforations Large hole in center, glazed on one side Thermal Shock Resistance - average coefficient of expansion from 20 to 200°C is 3.56 x 10-5, gradually increasing to 4.69 x 10-5 at 1050°C Heated tested porcelain Glaze - no softening occurs up to 1000°C, and is extremely white Resistance to Chemical Action - resistance to acids and alkalis is excellent (exception hydrofluoric acid)