Application
Paint can be applied as a liquid, as a solid, or as a gaseous suspension. Techniques vary depending on the practical or artistic results desired.
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 highly 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.
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.
History
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
