Article: Yuteki Tenmoku: The Oil-Spot Tea Bowl Japan Made a National Treasure
Yuteki Tenmoku: The Oil-Spot Tea Bowl Japan Made a National Treasure
Oil spots are not painted. They are iron, brought to the surface by heat.
Look into an oil-spot tenmoku bowl and the black is not flat. Thousands of silver-grey droplets sit in the glaze, catching light the way a night sky does. Tilt the bowl and they move.
This glaze has a name - yuteki tenmoku - and a history that runs from Song-dynasty China through the tea rooms of Japan's warlords to three bowls that Japan has designated National Treasure and Important Cultural Property. Here is what it is, why so little of it exists, and what to look for if you want to own a piece.
What is yuteki tenmoku?
Yuteki means “oil droplet.” The spots read as oil on water, or as stars.
Tenmoku is the Japanese name for a family of dark, iron-rich glazes. The word comes from Mount Tianmu in Zhejiang, China, where Japanese monks studying at the mountain temples encountered dark tea bowls and carried them home.
Yuteki means “oil droplet.” Yuteki tenmoku - oil-spot tenmoku - is the version in which the black glaze is scattered, inside and out, with round silvery spots that shine like precious metal. The technique began in the twelfth and thirteenth centuries at the Jian kilns of southern China, under the Southern Song.
The bowls reached Japan and were prized immediately. Seto potters began making their own versions. By the age of the warring states, oil-spot tenmoku was beloved of samurai lords and tea masters alike - Oda Nobunaga, Toyotomi Hideyoshi and Sen no Rikyū all owned pieces.
How the pattern is made
A pair. The spots differ on each piece, because the kiln decides them.
Oil spots are a form of kiln transformation - in Japanese yōhen: the pattern is not applied by the maker, but produced by what happens to the glaze inside the kiln.
Iron in the glaze rises as the glaze melts, gathers at the surface and cools into droplets. Their size, their spacing and their colour are decided by heat and by chemistry. The maker can steer the outcome; nobody can dictate it.
That is why no two pieces are the same, and why each one carries its own gradation from black to silver to brown.
The bowls Japan made National Treasures
The National Treasure bowl is finished with a gold rim, kinpukurin. This Arita bowl is finished the same way.
Three oil-spot tenmoku tea bowls in Japan carry official designation. One is a National Treasure; two are Important Cultural Properties.
The National Treasure was made in the Southern Song, after the Jin had taken the north, and is held today at the Museum of Oriental Ceramics, Osaka. Its rim is bound in gold - kinpukurin, a finish that both decorates and strengthens the lip - and oil spots cover the bowl inside and out.
It reached Japan in the Kamakura period, and its list of owners reads like a history of the country: the shogun Ashikaga Yoshimasa; Toyotomi Hidetsugu; the temple of Nishi Hongan-ji; the Mitsui family of Kyoto; the Sakai Wakasa family; the trading house Ataka & Co. When Ataka collapsed after the war the bowl passed to the Sumitomo group, which gave it to the city of Osaka. That is how it came to the museum.
The two Important Cultural Properties are quieter. One is at the Kyushu National Museum, fired in the Southern Song at the Jian kiln in Shuiji, in northern Fujian; its box is inscribed yuteki in the hand of Sen no Rikyū or Furuta Oribe. The other is at Ryoko-in, Daitoku-ji in Kyoto, where it is said to have arrived in 1610, when the son of the tea master Tsuda Sōgyū became the temple's 156th abbot.
If you want to see one: the National Treasure is on permanent display in Osaka except when it travels. The two Important Cultural Properties are not normally on view - check the museum and the temple for announcements.
Why so little of it exists
Oil-spot glaze cannot be produced in quantity. The chemical change that makes the spots happens only within a narrow window, and even when it happens the result differs from piece to piece. A firing that works does not guarantee that the next one will.
That scarcity, combined with a beauty that is never twice the same, placed oil-spot tenmoku close to the centre of Japanese taste - to wabi-sabi, the beauty of the imperfect and impermanent, and to yūgen, the sense of depth that cannot be stated outright. Historically these were tribute pieces, given to lords and to the court.
Choosing a piece to use today
- Decide whether you want to look at it or drink from it. A chawan - matcha bowl - is wide and shallow, made to be held in two hands and to show the whole field of spots at once. A yunomi teacup or a mug puts the same glaze into daily use.
- Silver spots or brown. Silver oil-spot reads cool and metallic; the browner, tortoiseshell-toned versions read warmer. Both are the same technique, taken to different points.
- Look at the rim. A gold rim follows the historical kinpukurin finish and lifts the black. An unrimmed piece is plainer and quieter.
- Expect the piece to differ from the photograph. The spots are made by fire, so the one you receive will not match the picture exactly. That is the nature of the glaze, not a defect.
A note on care
Gold and platinum finishes are the reason these pieces are washed by hand.
These are porcelain pieces with metallic, reduction-fired glazes. Wash by hand in warm water with a soft sponge, and avoid abrasive cleaners, which dull the surface. Pieces decorated with gold or platinum must never go in a microwave.
See the work
Oil-spot tenmoku on JTOPIA runs from matcha bowls made to be held and looked at, to teacups, rice bowls and coffee cups for the table.
