Urushi tree

Concurrently, the Egyptians, Japanese, and Chinese were beginning to develop lacquers (Stillman, I960). Some time before 200 b.c., the Chinese used the exudation (sap) from the conifer Rhus vemicifera (which became known as the sumac or varnish tree) as a coating. This plant has also been called the urushi tree. The tree belongs to the same family as the poison ivy plant, and like it, all parts of the tree are toxic— tree, sap, and latex. Those who tap the tree must wear gloves and protective clothing. The active irritant is urushiol, a catechol derivative. 

Technical examination of objects coated with a protective covering derived from the sap of a shrubby tree produces information that can be used to determine the materials and methods of manufacture. This information sometimes indicates when and where the piece was made. This chapter is intended to present a brief review of the raw material urushi, and the history and study of its use. Analytical techniques have included atomic absorption spectroscopy, thin layer chromatography, differential thermal analysis, emission spectroscopy, x-ray radiography, and optical and scanning electron microscopy these methods and results are reviewed. In addition, new methods are reported, including the use of energy dispensive x-ray fluorescence, scanning photoacoustical microscopy, laser microprobe and nondestructive IR spectrophotometry. 

Raw lacquer is called urushi. For our knowledge of the composition of urushi and the complex hardening process of the thin film layers, we now rely primarily on the recent work of Kumanotani and his coworkers (1-7). The sap of the Japanese lacquer tree is a latex containing 20-25% water, 65-70% urushic acid (urushiol), approximately 10% gummy sub-... 

The first paper mill was buUt by Eiichi Shibusawa in Tokyo in 1872. Some tons of natural rubber were imported from India and the USA in 1880-1890 and, concurrently, a rubber manufacturing company was buUt (1886). Celluloid products were first imported from Germany in 1877, and their domestic production started around 1890. The most interesting example is the Japanese urushi lacquer made from the poison oak tree. Because of its bright and clear color, the lacquer has been widely used from commodity to art works in Japan. In 1883, Hrkorokuro Yoshida published a research article on the urushi lacquer, describing an enzyme (later named laccase) that initiated the polycondensation of urushiol [5]. After 1903, scientific study on the urushi lacquer was continued by RUcou Majima [6]. 

Cardanol is a main component of thermally treated cashew nut shell liquid (CNSL), and is a phenolic compound with a long unsaturated hydrocarbon chain substituted in the meta position (Figure 2.17a). Urushiol, which is obtained from lacquer tree, poison ivy, poison oak, and poison sumac (Toxicodendron), and used for a raw material of a lacquer (urushi) in East Asia, is also a phenolic compound of catechol with a long unsaturated or saturated hydrocarbon chain (Figure 2.17b). Cardanol-based polymers have been reported very often, while there are a few research reports on urushiol-based polymers. Research on polymers synthesized from cardanol or CNSL are reviewed elsewhere.In the late 1980s, cardanol or CNSL-based polymers began to be reported as novel phenol-formaldehyde type resins and novel epoxy resins.Thereafter, Pillai and his co-workers have vigorously studied synthesis of various type of cardanol-based polymers polymers obtained... 

The oriental lacquer is prepared from the sap of the varnish tree" Rhus verni-ciflua, which is an emulsion of an aqueous phase and an organic phase called urushi-ol. The urushi fraction consists of a mixture of catechol derivatives substituted in 3-po-sition with aliphatic C- 5 or C- 7 side chains. About 60% of these side chains are trie-nes. The structure of the trienes is similar to that in linseed or tung oil and is essential for the effectiveness of the oxidative curing of oriental lacquer. We have utilized new techniques and used combinations of modern techniques to analyze the urushiol mixtures and to characterize and identify each individual compound. We have also developed ultraviolet stabilizers for oriental lacquer, stabilizers that could be incorporated into the polymerizing mixture during the curing process to result in ultraviolet stabilized oriental lacquer. 

The difference between the oriental lacquer trees of the Rhus variety and the rubber tree is that the rubber trees have polyisoprene as the desirable ingredient while the urushi components are mixtures of substituted catechol derivatives. 

The sap of the Japanese, lacquer tree consists of a water/ oil emulsion, the "oily" or urushi-ol fraction (about 65%) and an aqueous fraction (35%) which contains water-soluble plant gums and polysaccharides as well as small amounts of enzymes. Urushi-... 

For the preparation of lacquer ware, the oriental lacquer is usually applied on cedar wood, particularly from the Japanese cedar tree because it is the most warp resistant wood. One coat or two coats of primer, unprocessed urushi sap is applied followed by subsequent very thin layers (from twenty to forty layers) of processed "raw urushi" lacquer, one layer at the time every one or two days per application and curing. High relative humidity at the time of application and during curing is very critical it must be in the range from 65 to about 80%. ... 

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