 Around 1000 BC, the Chinese apparently realized that the ash covering the pieces was causing the glaze so they started adding the ash as a glaze before the pot went into the kiln.Ash glaze was the first glaze used in East Asia, and contained only ash, clay, and water.One of the ceramic fluxes in ash glazes is calcium oxide, commonly known as quicklime, and most ash glazes are part of the lime glaze family, not all of which use ash.