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Lacquer
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In a general sense, lacquer is a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required.
The term lacquer originates from the Portuguese word for lac, a type of resin excreted from certain insects.
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Encyclopedia
In a general sense, lacquer is a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required.
The term lacquer originates from the Portuguese word for lac, a type of resin excreted from certain insects. Regardless, in modern usage, lac-based varnishes are referred to as shellac, while lacquer refers to other polymers dissolved in volatile organic compounds (VOCs), such as nitrocellulose, and later acrylic compounds dissolved in lacquer thinner, a mixture of several solvents typically containing butyl acetate and xylene or toluene.
While both lacquer and shellac are traditional finishes, lacquer is more durable than shellac.
Urushiol-based lacquers
True lacquerwork is Chinese or Japanese in origin. According to Encyclopędia Britannica, varnish resin derived from a tree indigenous to China, species Toxicodendron vernicifluum, commonly known as the varnish tree. The manufacturing process was introduced into Japan and remained secret for centuries. 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.
Urushiol-based lacquers differ from most others, being slow-drying, water-based, and set by oxidation and polymerisation, rather than by evaporation alone. In order for it to set properly it requires humidity and warm temperature. 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 and fairly resistant to mechanical stress. Lacquer skills became very highly developed in India and Asia, and many highly decorated pieces were produced. The process of lacquer application in India is different from China and Japan. There are two types of lacquer: one obtained from the Rhus tree and the other from an insect. In India the insect lac was once used from which a red dye was first extracted, later what was left of the insect was a grease that was used for lacquering objects. Insect lac was introduced to India from Persia (Iran). The fresh resin from the Rhus trees causes urushiol-induced contact dermatitis and great care is required in its use. The Chinese treated the allergic reaction with shell-fish.
The contemporary theory held that from China, knowledge of lacquer technology was introduced to Korea, and from there to Japan. It was believed that Japan had also been using lacquer from ancient times, but the systematic process of application was developed by the Chinese. With the discovery of lacquer ware in Japan dating back to Jomon period, conflicting theories claim that technology may have been independently developed in Japan. Trade of lacquer objects traveled through various routes to the Middle East. Known applications of lacquer in China included coffins, plates, music instruments and furniture. Lacquer mixed with powdered cinnabar is used to produce the traditional red lacquerware from China.
The trees must be at least 10 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 (called "furo" or "muro" in Japanese, meaning "a bath" or "a room") 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. Unlike Japanese and Chinese Rhus verniciflua resin, Burmese lacquer does not cause allergic reactions; it 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 archeological 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.
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