demonstration testing at urushi liquid bidding
Fig. U1   heratate, a
demonstration testing at
an urushi liquid bidding:
Nihon Urushikakigijutu
Hozonkai, Joboji, Iwate,
URUSHI LIQUID   Urushi is obtained as sap Fig. U1 from the urushi tree 'RhusVerniciflua' which originally comes from the Himalayas. The urushi tree is to be found mostly in Southeast Asia, particularly in countries such as Japan, China, Korea, Taiwan, Vietnam, Burma, Cambodia, Bhutan and it prefers a warm climate. Mango, cashew nut and pistachio are also family of the urushi tree.

urushi flower
Fig. U2   urushi flower:
Nihon Urushikakigijutu
Hozonkai, Joboji, Iwate,
Urushi tree has the distinction of sex. Fig. U2 The female tree produces seeds that are rich in plant wax, while producing little urushi liquid. The seeds used to be fed to domestic animals for their high calories and to make candles out of them. The male tree produces no seeds, but more urushi instead. After the harvest the tree was used for floats and stakes for along the waterside, because of the light structure and corrosion resistant properties of the urushi in the tree.

urushi trees and kakitori
Fig. U3   urushi trees and
kakitori: Nihon Urushi-
kakigijutu Hozonkai,
Joboji, Iwate, Japan
The bark of the male tree is softer than the female tree and a male tree with a softer bark produces even more urushi liquid. In fact the urushi tree is a weak tree with a soft structure. Once the stem is damaged the tree will start rotting from the damaged area. In an attempt to fight this rotting process the wound produces a liquid with sterilizing properties, which dries fast and turns solid in humid air. In this way the tree tries to protect the wound from further damage. This surface is durable and proof against acid, alkali, oil, and high temperatures. By recent researches about chemical behaviour of urushi liquid, it is found that many kinds of bacteria, for example salmonella, colon bacillus, yellow staphylococcus, will be sterilized, meaning the number of bacteria is zero after 24 hours time span on an urushi lacquered surface.

In Japan the tree takes fifteen to twenty years to reach a height of three meters. When the stem of the urushi tree reaches a diameter of 15 to 20 cm the urushi-liquid can be extracted; this process is called kakitori
Fig. U3. Small incisions are made locally on the bark, in such a way that the liquid can be captured. In Japan, this process is repeated every 4 to 5 days, from the middle of June until the end of October. 700 to 1000 incisions are made on each urushi tree and at the end of October, one big cut is made around the outline of the tree to squeeze the last drops out. After this the tree dies. Depending on the size of the tree, one urushi tree can produce only 150 to 250 cc of raw urushi.

URUSHI TABLE   Fig. U4   The various kind of urushi that are used for both production and conservation. The upper row shows raw urushi. Number (Ⅰ) is Chinese, (Ⅱ) is regular Japanese, and (Ⅲ) is the best quality Japanese urushi.
Fig. U4   urushi table: Ⅰ. Chinese raw urushi / Ⅱ. Japanese ki-urushi / Ⅲ. Japanese kijomi-urushi / A. nakanuri-urushi / B. nashiji-urushi / C. kijiro-urushi / D. roiro-urushi / E. jo-nashiji-urushi / F. jo-kijiro-urushi / G. ikkake-urushi / H. jo-roiro-urushi/ a. nori-urushi / a'. rice powder / b. mugi-urushi / b'. wheat/ c. kokuso / c'. fibers / c"'. wood powder / d. sabi-urushi or ji / d". whetstone powder / d". baked clay powder/ e. - l. iro-urushi, coloured urushi / m. takamakie-urushi / n. rose-urushi / o. e-urushi / p. hiragaki-urushi / / e'. - l'. pigments

Both Chinese (Ⅰ) and Japanese (Ⅱ,Ⅲ) raw urushi (ki-urushi) are made of the main substance urushiol that polymerizes with the help of the catalyst laccase. It consists of a complex intermix of soft and hard structures which makes the urushi layer strong and lasting. The more urushiol the urushi contains the stronger the layer. The liquid contains in (Ⅱ) more than in (Ⅰ), and in (Ⅲ) more than in (Ⅱ) urushiol. The appearance of the darker colour demonstrates the quicker bonding with oxygen.

The main substance of the Vietnamese Rhus Succedanca is laccol. The Cambodian, Burmese and Thai M. Usitata contain thitsiol. The other sub-ingredients are gum, nitrogenous substance, oil and water. The difference in substance composition from particular districts developed their own adapted techniques. For example, the price of Japanese urushi is five to six times higher than that of other countries, as it is highly homogenized, it dries strongly solid within a thin layer and the results are extraordinary good and cannot be compared to other kinds of urushi. Since this durable thin urushi layer has properties to grip firmly onto fine metal grains, the maki-e technique could be developed in Japan only.

From the Chinese ki-urushi moisture is evaporated to produce the following variations: (A) nakanuri-urushi for middle layer coating, (B) mixed with gamboge (vegetable resin sort) makes nashiji-urushi for the middle layer, (C) natural coloured kijiro-urushi and (D) mixed with iron hydroxide which gives the black roiro-urushi.

The ki-urushi is further used for the treatment of wooden bodies. Glue made from rice powder (a') is mixed with it to gain nori-urushi (a) an adhesive agent. Mixed with wheat (b') this makes a strong adhesive agent, mugi-urushi (b). Fibers (c') and wood powder (c") is mixed with nori-urushi (a) to make kokuso (c) a filling component. Mixture of whetstone powder (d'), volcanic ash or baked clay powder (d"), water, and ki-urushi gives ji or sabi-urushi (d) used for ground layer coating and filling.

From Japanese ki-urushi (Ⅱ) moisture is evaporated for natural coloured jo-kijiro-urushi (F). This mixed with gamboge gives jo-nashiji-urushi with a high transparency (E). Ikkake-urushi has little moisture with a high viscosity (G). Mixed with iron hydroxide the most profound black urushi is gained, the jo-roiro-urushi (H).

Jo-kijiro-urushi is mixed with various kinds of pigments to produce iro-urushi (e to l). Jo-kijiro-urushi mixed with ikkake-urushi and pigments give takamakie-urushi (m).

Kijomi-urushi (Ⅲ) is used for the protection and glossing of the surface layer. Hiragaki-urushi (p) and e-urushi (o), both used for makie, are also made from kijomi-urushi. Jo-roiro-urushi (H) and kijomi-urushi make the rose-urushi (n), which is used for the gradation technique of togidashi-makie.

Nowadays there is an abundant supply of coloured urushi besides the traditional urushi.

Although (Ⅰ), (Ⅱ) and (Ⅲ), as well as (A) to (H) are available on the market, (a) to (p) should ideally be made by hand depending on the purpose. In this process the thickness and drying speed of the urushi can be controlled. The shortest time in which urushi can dry is approximately 20 minutes, but when certain areas need to dry slowly, the drying method can vary according to the purpose. For example, for the restoring of exfoliation mugi-urushi (b) is used. Despite the great adhesive power of this urushi, it takes one to four weeks to gain the desired result. The condition of the adhesive agent can be checked daily on superfluous mugi-urushi, and minor adjustments can still take place during the first few days. This implies that the slow drying speed minimizes the chance on failure. It can be concluded from Figure U4 that urushi with urushiol as main substance forms the origin for the components of adhesive agent, filling, paint, protection and glossing. The main difference with the japanning technique is that japanning makes use of various materials from different origins. This is a critical point. Using urushi for the treatment of the whole object makes the speed of aging simultaneous and well balanced. This is the reason that it is preferable to use materials of the same origin for the conservation of urushiware.

TOOLS   Fig. U5   On this photo are the tools for urushi work. They are specially designed for the characteristics of the viscous urushi and fine decoration material, and are therefore irreplaceable by substitute tools. Both production and conservation of urushi are unimaginable without the combination of appropriate material, tools and technique.
Fig. U5   tools: 1. spatulas made of Japanese cypress (hinoki-bera) / 2. brushes for urushi painting (urushi-bake) / 3. brushes for urushi painting for makie (jinuri-fude) 4. brushes for fine makie (makie-fude) 5. brushes for polishing, abrading and whetting (migaki-bake) / 6. dusting feather / 7. small palette for on the thumb (tsume-ban) / 8. spoon for metal grains (fun-saji) / 9. cylinders for sprinkling grains (funzutsu) / 10. brush for makie-powder dusting (kebo) / 11. a pair of bamboo tweezers for metal leaves (haku-basami) / 12. cleaning brushes (botan-bake) / 13. waterproof sandpaper (kami yasuri), #100 to #2000 are available / 14. synthetic whetstones (gousei-toishi), #400 to #4000 are available / 15. whetting charcoals (sumi) / 16.-17. kiridashi / 18. kuri-kogatana / 19. nushiya-bochyo

Fig. U6   urushi-bake, painting brush
Fig. U6   It is interesting to know that the brushes (nr. 2 in figure U5) for painting are made from girls' hair as a core. When the brush top gets worn out, it can be shaped again as a pencil.

bodies for urushi work
Fig. U7  bodies for urushi work
BODIES   Fig. U7   For urushi bodies are used: wood (moku-tai), bamboo (ran-tai), paper (ikkanbari), cloth (kanshitsu), hide/leather (shippi), metal (kin-tai), non-glazed ceramic (to-tai) and plastic. According to the shape the urushiware must be formed, distinguish is made between the tree varieties.

Used to make square objects (ita-mono or sashi-mono) are: hinoki, Chamaecyparis obtusa, a Japanese cypress; sawara, Chamaecyparis pisifera; hiba, Thujopsis dolabrata var. hondai; asunaro, Thujopsis dolabrata; sugi, Cryptomeria japonica; keyaki, Ulmus parvifolia; kuwa, mulberry; hou, Magnolia obovata; icho, Ginkgo biloba; kiri, Paulownia tomentosa; shioji, Fraxinus spaethiana; and katsura Cercidiphyllum japonicum. 

For round shaped designs that are made on the turning wheel (hiki-mono) are: keyaki; icho; shioji; tochi, Aesculus turbinata, a Japanese horse chestnut; and buna, Fagus crenata, the beech.

For round wooden chip boxes (mage-mono) are used: hinoki, sugi and katsura. Nowadays plywood is also used for bodies.

As cloth are usually used cotton and hemp cloth. Except for above mentioned body material turtle shells, horns, bottle gourd, stones, metals, fibers, etc. can be used. As long as the surface is non-oily and roughly textured almost any material can be utilized as body for the urushi work.

furo, drying cabinet
Fig. U7   Furo, drying cabinet
FURO   Fig. U8   Furo is the Japanese term for 'bath' with an origin of steam-bath in earlier times which in course of time was used as a drying cabinet which is important for the urushi work. The most specimen are made of wood and have sliding doors to keep the humidity inside and the dust outside. Depending on the time limit of drying the humidity degree can be adjusted. One cabinet should have a humidity of 50% or less (kara-buro), two others around approximately 60% and 80% (shimeshi-buro). Since the urushi tends to dry difficult when the temperature drops below 20 Celsius degrees, this can be controlled using hot-water bottles. The atmosphere within the furo is to be regulated according to the weather conditions.