Gosu

Also written as Gosu. A type of painting pigment used for ceramics. It is a mineral whose main component is cobalt oxide and contains some impurities, and is usually black-gray in color. When a design is drawn on the back of a transparent glaze using this gosu and then fired with a strong reducing flame, a cobalt blue-colored underglaze is obtained. In China, it is called Huiqing, Doqing, Shiqing, Mumyoui, Somarisei, Gayakiao, Kokushaseki, and Naidingshi, and in Japan, it is also called Iwakonjo and Chawangusuri. Cobalt appears as a coloring agent for colored glazes in the 8th century Tang sancai, but underglaze underglaze was first developed in Islam in the 9th century, and underglaze underglaze was also invented around the same time in China. In Japan, cobalt-colored blue and white porcelain was used in Mino ware in the 16th century, but it did not become popular until the 17th century, when Imari ware obtained Chinese gosu and began firing blue and white porcelain.

[Yoshiaki Yabe]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

呉洲とも書く。陶磁器に用いる絵付顔料の一種。酸化コバルトを主成分とし、若干の夾雑(きょうざつ)物を含む鉱物で、通常は黒灰色を呈している。透明釉(ゆう)裏にこの呉須を使って文様を描き、強力な還元炎で焼成すると、コバルトブルーに呈色する染付の呈発を得る。中国では回青、土青、石青、無名異、蘇麻離青(そまりせい)、画焼青、黒赭石(こくしゃせき)、内頂子などと称し、日本では岩紺青(いわこんじょう)、茶碗薬(ちゃわんぐすり)ともいう。コバルトは古くは8世紀の唐三彩に色釉の呈色剤として登場するが、9世紀にはイスラムで染付が創始され、中国でも同じころ染付がくふうされている。日本では16世紀に美濃焼(みのやき)でコバルト呈色の染付が行われたが、盛行するのは17世紀になって伊万里焼が中国製の呉須を入手して染付を焼造してからである。

［矢部良明］

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