Science in the Art of the Master Bizen Potter

摘要

Bizen stoneware, with the characteristic reddish hidasuki or “fire-marked” pattern, is one of Japan’s best known tradi-ntional ceramic works of art. The means of creating and controlling the various hues of the hidasuki pattern has remainedna mystery to outsiders for about a thousand years; the methods were known only to master potters who served under gen-nerations of master potters before them. In this Account, we present the results of 30 years of study in which we investi-ngated the microstructure and color-formation process in Bizen stoneware.nWe discovered that the hidasuki pattern results from the precipitation of corundum ( -Al2O3) and the subsequent epitaxialngrowth of hematite ( -Fe2O3) around it in a ∼50-µm-thick liquid specifically formed in the ceramic surface. The epitaxial com-nposites include hexagonal plate-like -Fe2O3/ -Al2O3/ -Fe2O3 sandwiched particles and also surprisingly beautiful flower-like crys-ntals, centered by hexagonal corundum crystals and decorated by several hexagonal hematite petal crystals. Bizen stoneware isnproduced from a unique clay that can only be mined from the Bizen area of Okayama Prefecture, Japan. The clay has an unusu-nally high Fe content compared with the traditional porcelain clay, as well as Si, Ca, Mg, and Na. Prior to firing, the Bizen worksnare wrapped in rice straw that was used originally as a separator to prevent adhesion. The hidasuki pattern only appears wherenthe rice straw is in direct contact with the clay; the rice straw supplies potassium, which reduces the melting point of the ceramicnsurface, thereby converting the contact area into a site for these reactions to take place. The effect is almost accidental and is pro-nduced without the aid of any artificial glazing and enameling. An unexpected variety of substances, including metallic iron coatednby graphite, Fe3P, and ε-Fe2O3, were also found to appear at low oxygen partial pressures.