Once the piece has been hot-formed, its temperature must be gradually lowered to avoid thermal shock which would cause it to burst. It is then placed in a special furnace, the annealing arch, in which the temperature drops from 806°F (430°C) to room temperature. Depending on the size and volume of the crystal piece, the annealing time can last from a few hours to several days. Great care is required when handling and placing the pieces in the kiln. Annealing is the last stage of the hot workshop.