Ash glaze, as the name suggests, is a glaze derived from ashes. The earliest such glazes can be traced back to the Shang period in China (c. 1500 B.C.), and it is thought they were produced accidentally, the result of white-hot wood ash being carried through the kiln with the draft of the fire and settling onto the pots, where the searing white heat melted it to a glass. Three thousand years later, wood ash remains an important and immensely popular...