page_title: Lacquer
section_title: Urushiol-based lacquers
hierarchical_section_title: Lacquer / Urushiol-based lacquers
caption_attribution_description: Colored Whisles from Channapatna
context_page_description: The term lacquer is used for a number of hard and potentially shiny finishes applied to materials such as wood or metal. These fall into a number of very different groups.
  The term lacquer originates from the Sanskrit word lākshā representing the number 100,000, which was used for both the lac insect and the scarlet resinous secretion, rich in shellac, that it produces that was used as wood finish in ancient India and neighbouring areas.
  Asian lacquerware, which may be called "true lacquer", are objects coated with the treated, dyed and dried sap of Toxicodendron vernicifluum or related trees, applied in several coats to a base that is usually wood. This dries to a very hard and smooth surface layer which is durable, waterproof, and attractive in feel and look. Asian lacquer is sometimes painted with pictures, inlaid with shell and other materials, or carved, as well as dusted with gold and given other further decorative treatments.
  In modern techniques, lacquer means a range of clear or coloured wood finishes that dry by solvent evaporation or a curing process that produces a hard, durable finish.
context_section_description: Urushiol-based lacquers differ from most others, being slow-drying, and set by oxidation and polymerization, rather than by evaporation alone. In order for it to set properly it requires a humid and warm environment. The phenols oxidize and polymerize under the action of an enzyme laccase, yielding a substrate that, upon proper evaporation of its water content, is hard. These lacquers produce very hard, durable finishes that are both beautiful and very resistant to damage by water, acid, alkali or abrasion. The active ingredient of the resin is urushiol, a mixture of various phenols suspended in water, plus a few proteins. The resin is derived from trees indigenous to East Asia, like lacquer tree Toxicodendron vernicifluum, and wax tree Toxicodendron succedaneum. The fresh resin from the T. vernicifluum trees causes urushiol-induced contact dermatitis and great care is required in its use. The Chinese treated the allergic reaction with crushed shellfish, which supposedly prevents lacquer from drying properly. Lacquer skills became very highly developed in Asia, and many highly decorated pieces were produced.
  During the Shang Dynasty (1600–1046 BC), the sophisticated techniques used in the lacquer process were first developed and it became a highly artistic craft, although various prehistoric lacquerwares have been unearthed in China dating back to the Neolithic period and objects with lacquer coating in Japan from the late Jōmon period. The earliest extant lacquer object, a red wooden bowl, was unearthed at a Hemudu culture (5000–4500 BC) site in China. By the Han Dynasty (206 BC – 220 AD), many centres of lacquer production became firmly established. The knowledge of the Chinese methods of the lacquer process spread from China during the Han, Tang and Song dynasties. Eventually it was introduced to Korea, Japan, Southeast and South Asia.
  Trade of lacquer objects travelled through various routes to the Middle East. Known applications of lacquer in China included coffins, music instruments, furniture, and various household items. Lacquer mixed with powdered cinnabar is used to produce the traditional red lacquerware from China.
  The trees must be at least ten years old before cutting to bleed the resin. It sets by a process called "aqua-polymerization", absorbing oxygen to set; placing in a humid environment allows it to absorb more oxygen from the evaporation of the water.
  Lacquer-yielding trees in Thailand, Vietnam, Burma and Taiwan, called Thitsi, are slightly different; they do not contain urushiol, but similar substances called "laccol" or "thitsiol". The end result is similar but softer than the Chinese or Japanese lacquer. Burmese lacquer sets slower, and is painted by craftsmen's hands without using brushes.
  Raw lacquer can be "coloured" by the addition of small amounts of iron oxides, giving red or black depending on the oxide. There is some evidence that its use is even older than 8,000 years from archaeological digs in China. Later, pigments were added to make colours. It is used not only as a finish, but mixed with ground fired and unfired clays applied to a mould with layers of hemp cloth, it can produce objects without need for another core like wood. The process is called "kanshitsu" in Japan. Advanced decorative techniques using additional materials such as gold and silver powders and flakes ("makie") were refined to very high standards in Japan also after having been introduced from China. In the lacquering of the Chinese musical instrument, the guqin, the lacquer is mixed with deer horn powder (or ceramic powder) to give it more strength so it can stand up to the fingering.
  There are a number of forms of urushiol. They vary by the length of the R chain, which depends on the species of plant producing the urushiol. Urushiol can also vary in the degree of saturation in the carbon chain. Urushiol can be drawn as follows:
  , where:
  R = (CH₂)₁₄CH₃ or
  R = (CH₂)₇CH=CH(CH₂)₅CH₃ or
  R = (CH₂)₇CH=CHCH₂CH=CH(CH₂)₂CH₃ or
  R = (CH₂)₇CH=CHCH₂CH=CHCH=CHCH₃ or
  R = (CH₂)₇CH=CHCH₂CH=CHCH₂CH=CH₂
caption: Wooden lacquer-finished whistles made in Channapatna, Karnataka, India
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