Depending upon your sense of history, you could say that the airbrush was invented as far back as 1876. Francis Edgar Stanley, the same person who with his brother invented the Stanley Steamer, patented a “paint distributor/atomizer” to continuously coat plates used in photography. However, the first device to be called an “airbrush” was developed by Abner Peeler “for the painting of watercolors and other artistic purposes”.
The airbrush, a small, hand-held tool that sprays ink, dye or paint, has gone through several changes through the years, but still operates on the same principle. Compressed air causes the paint (or ink or dye) to pass through a pen-like body with a very fine needle which in turn produces a fine spray that is applied on various surfaces. The ink or paint passing through the needle is controlled by the person using the airbrush with a variable trigger mechanism. In simpler terms: air and paint mix then go through the needle onto the surface to be painted.
Trigger Action - An airbrush may be a Single-Action or Double-Action type. In the Single-Action airbrush, the single act of depressing the trigger causes the paint and air to flow into the airbrush body which atomizes the paint and disperses it onto the target surface. With the Double-Action type, there are two separate mechanisms, one which controls the flow of air and the other the flow of paint. This enables greater control of the outflow and a wider variety of artistic effects.
Feed System - Another way of classifying an airbrush is through its Feed System. The paint container of the airbrush may be located at the top, bottom or side of the body. Positioning the container at the top of the body does not require air and uses the pull of gravity to draw the paint into the body. This is referred to as a Gravity Feed airbrush. A Gravity Feed airbrush delivers the finest spray and is the choice for work that demands a lot of detail. When the container is situated at the bottom or at the side , this is called a Suction Feed airbrush because the paint is suctioned into the body. A Suction Feed airbrush may come in Bottom Feed and Side Feed varieties. This type of airbrush has the advantage of giving the user visibility over the top of the body. Some Side Feed varieties even come in left-handed or right-handed versions to suit the individual artist's preference. A Bottom Feed variety can have larger paint containers than the other types. This makes it ideal for large scale jobs.
Mix Point – Still another way of classifying an airbrush is by its Mix Point. An Internal Mix airbrush is one where the air and paint mix in the tip at the same time, resulting in a finer mist. With an External Mix type, the air leaves the airbrush before it comes into contact with the paint, creating a coarse spray. External Mix types are preferred for more viscous paints and for spraying large areas.