Yohen
Yohen (Japanese: 窯変) is a term used in Japanese ceramics to describe changes in the appearance of pottery caused by unexpected transformations during firing in the kiln. The word literally means "kiln change" or "kiln transformation".
Yohen effects occur when variations in temperature, atmosphere, flame movement, or ash deposits interact with the clay body and glaze during firing. These conditions can produce unusual colors, surface textures, or glaze patterns that were not intentionally planned by the potter.
In traditional wood-fired kilns, such as those used in Anagama firing and Noborigama firing, pottery may experience different firing environments depending on its position inside the kiln. Ash carried by the flames, shifting temperatures, and changes in airflow can create dramatic visual variations on the surface of ceramic pieces.
Some yohen effects have become highly valued in Japanese ceramic traditions. Certain rare glaze transformations, especially in tea ceramics, may be regarded as particularly beautiful and unique results of the firing process.
Because kiln conditions are complex and difficult to control precisely, yohen effects are often unpredictable. Each piece that develops such transformations may display distinctive visual characteristics.
