Tenmoku Glaze: Exploring Origins, Techniques, and Colors

Tenmoku glaze, also known as “temmoku” and “temoku,” holds a rich history and mesmerizing allure. Originating from the imitation of Chinese Jian ware during the southern Song dynasty, Tenmoku has found its place in both China and Japan. Let’s delve into the captivating world of Tenmoku glaze and its journey through time.

Origins and Aesthetic

Tenmoku glaze emerged as an attempt to recreate the magnificent Chinese Jian ware tea bowls. These tea bowls, characterized by their conical shape and slight indent below the rim, stood approximately 4-5 inches in height. However, the true essence of Jian ware lies in its ceramic glaze, which offers a myriad of distinct effects. Some of these effects possess an element of randomness, which holds a deep philosophical appeal to the Japanese. The tea-masters who developed the Japanese tea ceremony were instrumental in promoting the aesthetic and significance of Tenmoku pottery.

The Influence of Tianmu Mountain

The name “Tenmoku” derives from the Tianmu Mountain temple in China, where iron-glazed bowls were used for tea ceremonies. This style gained immense popularity during the Song dynasty and was referred to as Jian Zhan in Chinese, meaning “Jian (tea) cup.” Its association with the divine, as the English translation “Heaven’s Eye” suggests, adds to its mystique.

Cultural Exchange and Valued Treasures

Historical accounts reveal that the Ming Emperor Yongle sent ten Jian ware bowls to Ashikaga Yoshimitsu, the shōgun of Japan during the Muromachi period, in 1406. Additionally, Japanese monks who visited Chinese monasteries brought back these prized ceramics. As they became highly valued for tea ceremonies, more Jian ware pieces were imported from China. Today, three vessels from the southern Song dynasty hold such immense value that they have been designated as National Treasures of Japan. This cultural exchange resulted in the gradual adoption of the Japanese term “Tenmoku” to refer to this type of ware, replacing the original Chinese name.

Enduring Legacy in Japan

The production of Tenmoku glaze eventually took hold in Japan, where it continues to thrive. Seto ware kilns, renowned for their craftsmanship, particularly excelled in creating Tenmoku ceramics. Even today, a small circle of Japanese artists keeps the tradition alive, producing Tenmoku glaze with remarkable skill. Notable artists such as Kamada Kōji, Nagae Sōkichi, Hayashi Kyōsuke, and Oketani Yasushi contribute to the preservation of this ancient craft. Moreover, a renewed interest in Jian ware in China during the 1990s has allowed masters like Xiong Zhonggui from the village of Shuiji in Fujian to revive the production of Jian Zhan using the original raw materials.

The Magical Transformation of Tenmoku Glaze

Composition and Cooling: Tenmoku glaze, an enchanting ceramic finish, is crafted using a combination of feldspar, limestone, and iron oxide. Interestingly, the speed at which a piece is cooled plays a significant role in determining the depth of its black hue. The faster the cooling process, the darker the glaze becomes.

Formation of Iron Crystals

One of the distinctive features of Tenmoku glaze is its inherent variability. This is attributed to the interplay of various factors during the heating and cooling stages of production. The presence of iron in both the clay body and the glaze itself contributes to this effect. A lengthy firing process and a clay body infused with iron provide ample opportunities for the iron to migrate into the glaze. While the glaze is molten, the iron can either form surface crystals, giving rise to mesmerizing “oil spot” patterns, or remain within the glaze, producing a lustrous, glossy color. The occurrence of oil spots is more common in oxidation firing.

Cooling Time and Crystal Formation

The duration of the cooling phase influences the development of surface crystals in Tenmoku glaze. To maximize the appearance of these crystals, potters can adopt a technique known as “firing down.” Typically, during a regular firing process, the kiln gradually reaches its maximum temperature by continuously adding fuel. Once this temperature is reached, fueling ceases, and the kiln slowly cools by dissipating heat to the surrounding air. However, when firing down, the potter adds a limited amount of fuel after reaching the maximum temperature, intentionally prolonging the cooling process. This approach keeps the glazes in a molten state for an extended period, allowing ample time for surface crystals to form.

A Palette of Colors

Tenmoku glazes exhibit a captivating range of colors, from deep plum resembling the ripened flesh of a persimmon to vibrant yellow, warm brown, and profound black. Each variation adds its unique character to the finished piece, creating a visual feast for the eyes.

Two Prominent Glaze Types

Within the realm of Tenmoku glaze, two types stand out as particularly common: Youhen and Yuteki. These glazes represent distinct approaches to achieving the desired aesthetic and offer artists different avenues for creative expression.