備前焼“火だすき”の発色機構 ＩＩ

Abstract

The coloration of Hidasuki on Bizen-yaki is due to the formation of hematite. When a mixture of Bizen-clay and potassium chloride was heated at above 1150t, glassy phase was formed. Hematite was formed during the cooling process of the glassy phase. In this study the behavior of hematite in the heating and the cooling processes of biotite and in those processes of a mixture of biotite and potassium chloride were studied. Biotite which contains iron ions in its structure is found in a parent rock of Bizen-clay. When biotite was heated at 5001, its basal spacing decreased to form dehydrated phase I followed by gradual decrease of the basal spacing up to 1000°C. When biotite was heated at 1000°C, dehydrated phase 0 was formed and hematite appeared coincidentally. When mixtures of 8wt% of potassium chloride and biotite were heated, hematite was found at above 500°C and the basal spacing decrease in biotite was also found at 500°C. Hydrogen chloride was detected at above 570°C. Leucite was formed at 1100°C and glassy phase appeared at 1300°C. Part of the hematite dissolved in the glassy phase. When the glassy phase was cooled down slowly, hematite was recrystallized.