Lalique is one of the few crystal factories that still makes crucibles for its pot furnace. Leaving the pottery workshop, the pots, fitted with a lid, are placed in the furnace. After 20 hours of firing, they reach a temperature of 2,550°F (1,400°C). The lids are removed and replaced with a separately made earthen arch (photo) which completely seals the joint between the kiln and the pot. The inside of the pot is then rinsed to remove all impurities. The pot is ready to receive the raw material (a mixture of silica, lead oxide, potash and soda) which, when heated to a very high temperature, is transformed into molten crystal.