Glaze - porcelain

Japanese: 釉 - うわぐすり

Also called glaze. A glassy substance that is baked onto the surface of ceramics to give them beauty, strength, corrosion resistance, and eliminate moisture absorption. It must have a coefficient of expansion roughly equal to that of the base, and a melting point lower than that of the base. The main component is a silicate compound, and glazes are classified into lead glaze, alkali glaze, lime glaze, feldspar glaze, boric acid glaze, etc. depending on the characteristics of the flux. In addition to transparent glazes, there are also colored glazes that contain metal oxides, milky glazes, crystalline glazes, and matte glazes. In particular, when the glaze contains metals that act as coloring agents, the color often varies depending on the content and whether it is fired with an oxidizing flame or a reducing flame. Various glazes are also broadly classified into low-fire glazes and high-fire glazes based on their melting temperature. Among low-fire glazes, old alkaline glazes are used for Egyptian tiles, and lead glazes for Raku ware, Tang sancai, and green glazes. Ash glaze, which is representative of high-fired glazes, can be said to be the origin of celadon glaze, and ash-glazed pottery first appeared in China in the middle of the Shang (Yin) period, around 1300 BC. In Japan, it has been seen since the Heian period, and there are various types such as straw ash (opaque milky white) and chair ash (white porcelain glaze), but when it is made from pine ash, which has a high iron and alkali content, it reduces to become a green Vidro glaze. Feldspar glaze is made from weathered granite, and Shino ware is a typical example. Glaze baked onto a metal surface is called enamel.
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Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

釉薬(ゆうやく)とも。陶磁器の表面に焼き付けて美観，強度，耐食性などを与え，吸湿性をなくすために用いられるガラス質の物質。素地と膨張係数がほぼ等しく，溶融点が素地より低いことが必要。主成分はケイ酸化合物であり，融剤の特性により鉛釉，アルカリ釉，石灰釉，長石釉，ホウ酸釉などに分類される。透明釉のほか，金属酸化物を加えた色釉，乳白釉，結晶釉，つや消し釉などもある。とくに呈色剤となる金属を釉が含有する場合，その含有率や酸化炎焼成か還元炎焼成かで発色は異なることが多い。また各種の釉は，溶融温度から低火度釉，高火度釉に大別され，低火度釉のうち，アルカリ釉の古いものはエジプトのタイル，鉛釉は楽焼・唐三彩・緑釉に用いられている。高火度釉を代表する灰釉は，青磁釉の源流ともいうべきもので，灰釉陶器の初現は中国で商（殷）時代中期，前1300年ころにまで遡る。日本でも平安時代から見られ，わら灰（乳白色不透明），いす灰（白磁釉）など種々あるが，松の灰など鉄とアルカリ分が多いと，還元して緑のビードロ釉となる。長石釉は花コウ岩の風化したものを用い，その代表は志野焼である。金属表面に釉を焼き付けたものは琺瑯(ほうろう)という。
→関連項目井戸茶碗｜インチン（影青）｜鈞窯｜三彩｜磁器｜墨流し｜青磁｜【せん】｜象嵌｜染付｜鉄絵｜陶器｜陶磁器｜白磁｜モヘンジョ・ダロ

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