Crystalline glazes are special ceramic glazes in which zinc-silicate crystals grow inside the glaze while it is still very hot. The crystals begin as microscopic seeds in the glaze, which form in random numbers and locations. When the kiln is cooled to the proper temperature, crystals start to grow. In order for crystals to grow, the glaze must be very fluid. Much of the glaze runs off the vessel during the firing into a catch basin and pedestal that are specially made for each piece. After the firing, the piece is carefully separated from the pedestal with a hammer and chisel and the base is ground smooth.