Paint

For a glossary of terms used in the paint industry go to Oil & Colour Chemists' Association and click on Paintopedia.

Paint is the general term for a family of products used to protect and add color to an object or surface by covering it with a pigmented coating. It is also a verb meaning to apply such a substance.

Paint is also a military verb meaning to shine a targeting device (laser, radar, etc.) to designate an object as the target of an attack.

Paint can be applied as a liquid, as a solid, or as a gaseous suspension.

As a solid (usually in industrial and automotive applications), the paint is a applied as a very fine powder, then baked at high temperature. This melts the powder and causes it to adhere (stick) to the surface. The reasons for doing this involve the chemistries of the paint, the surface itself, and perhaps even the chemistry of the substrate (the overall object being painted).

As a gas or as a gaseous suspension, the paint is suspended in solid or liquid form in a gas that is sprayed on an object. The paint sticks the object. The reasons for doing this include:

the application mechanism is air and thus no solid object ever touches the object being painted;
the distribution of the paint is very uniform so there are no sharp lines
it is possible to deliver very small amounts of paint or to paint very slowly;
a chemical (typically a solvent) can sprayed along with the paint to dissolve together both the delivered paint and the chemicals on the surface of the object being painted;
some chemical reactions in paint involve the orientation of the paint molecules.

In the liquid application, paint can be applied by direct application using brushes, paint rollers, other instruments, or body parts. Examples of body parts include fingerpainting, where the paint is applied by hand, whole-body painting (popular in the 1960's avant-garde movement), and cave painting, in which a pigment (usually finely-ground charcoal) is held in the mouth and spat at a wall (NOTE: DO NOT DO THIS with modern paints, they are very, very toxic and this might cause death or permanent injury).

Paint may also be applied by flipping or spraying the paint, dripping, or by dipping an object in paint.

Paint is very common and is applied to almost every object. It is a method of producing art, an industrial coating, a driving aid (lane markings), a preservative (rust-prone steel auto bodies), on interior walls, on exterior surfaces exposed to weather, and myriad other uses.

With art, it has also been used for centuries in the creation of great works, such as Leonardo da Vinci's Mona Lisa and Vincent Van Gogh's Starry Night.

There are generally three parts to a paint, a solid part, and two liquid parts. Combined, the two liquid parts make up the medium or vehicle. The solid part is mostly pigments, which are particles that provide color and also help make the paint opaque. The binder (usually a natural or synthetic resin) is that part of the vehicle which eventually solidifies to form part the dried paint film. The solvent or diluent (often an organic solvent, or water) is that part of the vehicle that is volatile and does not become part of the paint film. The major function of the solvent is to thin the paint to make it easy to apply.

After application, the liquid paint solidifies, leaving the binder and pigment as a colored coating. Depending on the type of binder, this hardening may be a result of processes such as curing (in oil paint, this takes the form of oxidation of linseed oil to form linoxin), evaporation (most water-based paints are emulsions of solid binders in water; when the diluent evaporates, the molecules of the binder coalesce to form a solid film), cooling (encaustic, or wax, paints are liquid when warm, and harden upon cooling), etc.

Since the time of the Renaissance, siccative (drying) oil paints, primarily linseed oil, have been the most commonly used kind of paints in fine art applications; oil paint is still common today. However, in the 20th centry, water-based paints, including watercolors and acrylic paints, became very popular with the development of latex and acrylic pigment suspensions. Milk paints (also called casein), where the medium is derived from milk, were popular in the 19th century and are still available today. Egg tempera (where the medium is egg yolk) is still in use as well, as are encaustic wax-based paints.

Some newer paints can produce effects where the color changes depending on the angle (orientation) at which it is viewed. Modern U.S. currency, specifically the newer higher denomination notes, have this effect on them. This effect is produced by having pigement molecules that are long and thin and are meant to dry in an this-end-out configuration, with different ends of the molecule being different colors.

Poster paint has been used primarily in the creation of student works, or by children.

Pigment

Pigments, usually insoluble powders, are used both to provide color, and to make paint opaque, thus protecting the substrate from the harmful effects of ultraviolet light while also increasing a paint's hiding power.

Lead paint: White pigment does not add color, but serves the very important function of increasing opacity and making the paint resistant to UV radiation. For centuries, the primary white pigment in paints was white lead (also called lead white), one of the oldest pigments known. The problem with white lead is that it is extremely toxic. See lead.

It wasn't until the middle of the 20th century that white lead was generally replaced by a less toxic substitute, titanium white, which was first used in paints in the 19th century. The titanium white used in most paints today is actually a mixture of titanium dioxide (pure titanium white) and zinc oxide (zinc white). See pigment.

Similar products:

Wood stain is a product very similar to paint, except that it is much thinner, and formulated so that the pigment penetrates the surface rather than remaining in a film on top of the surface. Stain is predominantly pigment or dye and solvent (with little or no binder), designed primarily to add color without providing a surface coating.
Varnish and shellac provide a protective coating without changing the color. They are essentially paint without pigment. Unlike paint, which is opaque, varnish and shellac are clear or translucent.
Lacquer is usually a fast-drying solvent-based paint or varnish that produces an especially hard, durable finish.
An enamel paint is a paint that dries to an especially hard, usually glossy, finish. Enamel can be made by adding varnish to oil-based paint.
Fingerpaint

Historical notes from Household Cyclopedia:

Ancient painted walls, to be seen at Dendara, Egypt, although exposed for many ages to the open air, still possess a perfect brilliancy of color, as vivid as when painted, perhaps 2000 years ago. The Egyptians mixed their colors with some gummy substance, and applied them detached from each other without any blending or mixture. They appeared to have used six colors, viz., white, black, blue, red, yellow, and green. They first covered the field entirely with white, upon which they traced the design in black, leaving out the lights of the ground color. They used minium for red, and generally of a dark tinge.

Pliny mentions some painted ceilings in his day in the town of Ardea, which had been executed at a date prior to the foundation of Rome. He expresses great surprise and admiration at their freshness, after the lapse of so many centuries.

See also lacquer, varnish

A bitmap graphics editor may allow direct painting, e.g. Microsoft Paint, an electronic drawing and painting program.