Fambe 窑变 [yáo biàn] (lit. kiln-change)
Fambe is a porcelain-making technique used to create beautiful unique and unpredictable patterns. Fambe was originally the result of accidents during firing process - temperature changes in the kiln made the color and even the shape of the porcelain change. In modern practice the process is more controlled, but the aesthetic quality of the beautiful unpredictability remains.
In ancient times, fambe was literally considered an undesirable accident, and potters couldn't understand the process that led to it, thinking it was caused by evil spirits. This was especially considered unlucky in royal kilns, and fambed porcelains would be destroyed immediately. In one account recorded in a Song Dynasty (960 - 1279) notebook (清波杂志, Qing Bo Za Zhi) by Zhou Hui (周煇), one such incident is mentioned: "In Rao Jingdezhen, a porcelain changed color in the kiln, red as cinnabar. It was abnormal and must be evil, and the potter broke it immediately." ("饶州景德镇，大观间有窑变，色红如朱砂。物反常为妖，窑户亟碎之。" )
During the Qing Dynasty (1636 - 1912), the fambe process became more understood, and people started to admire its unique colors. Potters learned how to control the color glaze on the porcelains and the temperature in the kiln to make the fambe occur. The process became more controlled, but the unpredictable character of the porcelain remained, giving each particular item a unique look.
Jun Kiln (钧瓷 [jūn cí]), known for its Fambe style, is one of the most famous kiln styles in China. Jun Kiln originated in Yuzhou, Henan province, where the local clay and color glaze contain up to 40 different trace elements. These elements combined with certain kiln environments catalyze the creation of fambe. Besides this, the shape of the kiln, the thickness of the glaze, and the changing of the temperature can also affect the result. Even in a single firing process in the same kiln, each piece of porcelain in the batch can come out different because of its exact placement as well as other factors.
Yixing Clay can also have a look similar to 'Fambe'. Yixing clay doesn't have a glaze like porcelain, but the clay's different colors can also produce these "happy accidents". They are not considered to be in the Fambe Kiln style per se, but they have their own version of this unique and beautiful aesthetic.
Every Fambe piece is unique. The one you have is the only one in this world.