In the hot glass workshop, the traditional pot furnace is used to make coloured crystal. Each refractory clay pot or crucible contains a specific colour. The crucibles are arranged in a circle around a central flame fuelled by oil or gas. The glassmakers take the crystal paste from them, which is heated to 2,550°F (1,400°C). Each pot can contain 350 to 400 kg of molten crystal and its life span is limited to 4 months. Changing a crucible is a delicate task that is carried out without ever turning off the furnace. At Lalique, the crucibles are made on site by a team of specialist potters.