Lye. Lye is the supernatant of wood ash, hearth ash, etc. soaked in water, and is essentially soluble alkali salts. The reason why wood ash and clay ash are used as glazes for ceramics is to utilize the carbonate lime content they contain. Soluble alkali salts are harmful to the glaze and must be removed. The word “bad” in the pottery law book of the Keio period (1865-8), which describes the preparation of glazes for Gojosaka and Awata, refers to the ashes that have been removed, and the character “bad” was probably used exclusively for Gojosaka and Awata.
