For items made with lacquer, see Lacquerware.
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 (लाक्षा) representing the number 100,000, which was used for both the lac insect (because of their enormous number) 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.
In modern techniques, lacquer means a range of clear or pigmented coatings that dry by solvent evaporation to produce a hard, durable finish.
The finish can be of any sheen level from ultra to high gloss, and it can be further polished as required.
Lacquer finishes are usually harder and more brittle than oil-based or latex paints, and are typically used on hard and smooth surfaces.
In terms of modern finishing products, lac-based finishes are likely to be referred to as shellac, while lacquer refers to synthetic polymers such as nitrocellulose, cellulose acetate butyrate ("CAB"), or acrylic resin dissolved in lacquer thinner, a mixture of solvents such as ketones (acetone, MEK), esters (butyl acetate, methoxypropyl acetate), aromatic hydrocarbons (toluene, xylene), ethers (cellosolve), and alcohols.
Synthetic lacquer is more durable than shellac.
The English lacquer is from the archaic French word lacre "a kind of sealing wax", from Portuguese lacre, itself an unexplained variant of Medieval Latin lacca "resinous substance" from Arabic lakk, from Persian lak, from Hindi lakh (Prakrit lakkha).
Lac resin was once imported in sizeable quantity into Europe from India along with Eastern woods.
Lacquer sheen is a measurement of the shine for a given lacquer.
Different manufacturers have their own names and standards for their sheen.
The most common names from least shiny to most shiny are: flat, matte, egg shell, satin, semi-gloss, and gloss (high).
Main article: Urushiol
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 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.
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.
From the 16th century to the 17th century, lacquer was introduced to Europe on a large scale for the first time through trade with Japanese.
Until the 19th century, lacquerware was one of Japan's major exports, and European royalty, aristocrats and religious people represented by Marie-Antoinette, Maria Theresa and The Society of Jesus collected Japanese lacquerware luxuriously decorated with maki-e.
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
Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Lacquer.