- the beautiful sheen it acquires with use
- its fine grain, due to its extremely slow growth
- its unique, subtle aroma
- the pleasing sound stones make when played on it
- its extreme durability; kaya boards last for hundreds of years
- its texture, neither too hard nor too soft, bouncing back from the tiny indentations left by stones played
- long-term value, due to the small number of kaya trees available for harvesting
Itame is further categorized into "ura" (back) and "omote" (front). "Ura" boards are superior, with the center of the tree lying towards the top of the board, with no defects. In other words, the grain of the side surfaces facing the players forms the bottom half of a semi-circle. "Omote" boards have the center of the tree lying toward the bottom of the board (the grain of the side surface facing the players forming the top half of a semi-circle), with more noticeable grain on the surface and defects on the bottom.
How each is cut from the tree is shown here:
In this graphic, A is shihou-masa, the top grade of masame, requiring a tree at least 1.2m in diameter. B is masame, requiring uniform texture and grain. Depending on the cut, could be shihou-masa, tenchi-masa (straight grain on both top and bottom), or ten-masa (straight grain on top only). C is itame--ura, and D itame--omote. The red line indicates the surface of the board.
Prices for a kaya go board with attached legs (12-18 cm height, 4-6 sun) range from as little as USD $2,000 for itame/omote, up to USD $100,000 or more (masame); such boards weigh 14-20kg, with masame 1-2kg heavier than itame. Kaya table boards (6 cm height, or 2 sun) start at about USD600. Kaya table boards composed of joined pieces (setsugou-ban, 接合盤) are also available at lower prices. Prices depend on the origin and quality of wood, workmanship, and reputation of the maker.
Kaya must be dried before being made into boards. The drying is a painstaking process, involving wrapping both ends of the piece of wood in paper to avoid cracking, then placing it in a shaded drying room with no wind for six months for a 2-sun table board, one year for itame, and three years for masame, although five-year and even seven-year drying periods are also possible. According to Go Game Guru, 10 years of drying is recommended for kaya go boards. Of 50 pieces of material so dried, only 10 emerge from the process without cracks--another reason, in addition to the rarity of the material and the cost of capital and facilities costs for drying--that kaya boards are so expensive.
Shin Kaya, another material used for go boards, is not kaya at all, but rather spruce, a pale wood which requires finishing and is less long-lasting than kaya. Kaya may be called hon-kaya to distinguish it from such would-be imitators.
Thanks to its appearance, durability, and moisture resistance kaya is also used for religious statues such as of the Buddha, lacquered objects, furniture, and even bathroom fixtures.
Making one-piece go boards leaves a lot of the tree left over for other uses such as the table-top boards made from smaller pieces of wood joined together mentioned above. The wood is also used to make various smaller objects such as saucers (chataku), trays, boxes, etc. These small utilitarian objects are not too expensive.
Kaya ( Torreya nucifera, honoring John Torreya (1796-1873), American botanist and chemist), also known as Japanese nutmeg or Japanese torreya, is an evergreen tree with yellow to pale brown wood, smooth red bark, and spreading brownish branches. The kaya is durable under water. In autumn the plant is laden with large, edible seeds (like acorns or hazelnuts) which contain oil and have a resinous aftertaste. The color of cut kaya wood mellows with age.
Most often the kaya is found growing in moist, shady areas, seldom in the open. In the wild, kaya trees may reach 25m or more in height and 2m in diameter, requiring up to 500 years to reach that size. A simple calculation shows that a masame requires a diameter of a minimum of 90cm. Based on known growth data, such trees could need to be 400 to 500 years old.
Kaya grows throughout central and southern Honshu, Shikoku, and Kyushu (down to Yakushima). Hyuga kaya (日向かや)--from the ancient province of Hyuga, present-day Miyazaki Prefecture in Kyushu, is one well-known variety, used in many famous boards. Compared to Honshu kaya (本州かや), Hyuga kaya has an attractive variegated yellow tinge, although of course this comes at a price. Another popular type of kaya is Taisho-kaya (大正榧) from Kochi Prefecture.
Some writers call kaya taxus nucifera rather than torreya nucifera. This is how it was first classified by Linnaeus in 1753. Later, a Scottish Botanist, George Arnott, decided that Linnaeus’ Taxus nucifera belonged in a different genus, Torreya.
If kaya actually belonged in Taxus, we would have to stop using it.
Asian yews, genus taxus, produce the anti-cancer drug taxol/paclitaxel, but there are not nearly enough trees to provide all that could be used. They are on the World Wildlife Federation's 10 most wanted list of endangered species. After some fairly horrendous over-exploitation, they are now legally protected in China.
One paper on illegal logging Word format says:
- A chemical compound extracted from the bark, needles, twigs and roots of species of the genus Taxus called paclitaxel has been sucessfully used to treat some cancers – the drug is now the biggest selling cancer drug in the world. ...
- All species of Asian taxus are suffering from massive over-exploitation ... Just one treatment of paclitaxel requires the bark of 7.5 average sized trees. 3000 trees are needed to produce just 1kg of the drug, and current world demand is for more than 700kg.
One estimate is that by harvesting the entire world population of Taxus trees, you would get enough to give every patient that could use it one dose of the drug. Of course, effective treatment requires many doses.
The genus Torreya has been regarded as a member of the yew family, Taxaceae, along with the genus Taxus. However, some botanists put it in other families.
Related (botanical) links:
- "Torreya nucifera" at Plants for a Future Gives taxus nucifera as a synonym.
- search for "Torreya nucifera" at Spring Flowering