Airbrushes work on a fairly simple concept. The typical airbrush consists of a pressurized air supply hose and a small paint canister connected to a nozzle. The body of the airbrush is designed to be held like a pen. A small injector valve releases a steady stream of liquid paint into the jet of air supplied by the hose. The high velocity of the air has an atomizing effect on the paint, separating it into tiny droplets. The paint-air mixture is then propelled through a needle inside the nozzle, which regulates the flow, allowing an even consistency of paint to be projected from the nozzle.
Airbrushes are used for a wide variety of painting applications. They are particularly useful in distributing a thin but even layer of paint across a surface or for creating a smooth blend or fade effect with paint. Many people are familiar with the use of airbrushes to paint temporary tattoos. Airbrushes are also commonly used in creating artistic paintings, murals and illustrations due to the high level of control the artist has over the instrument's output. Stencils are commonly used in airbrush art. Hobbyists often use airbrushes to paint scale model components and professional car shops use airbrushes to apply custom paint jobs to automobiles. Professionally, airbrushes are often used to retouch photographs; this can be used to enhance the visual appeal of a product or model, or historically, to remove entire people or items from a photo. Cosmetically, airbrushing is used in Hollywood movie studios to apply makeup; it is also used for spray-on tanning and for fingernail art.
Airbrushes are categorized in a number of ways, and there are many different varieties of airbrush. The type used is mainly dependent on the application. Single-action airbrushes are used for basic painting purposes, and the mechanism is simple; depressing the trigger causes the paint and air to flow out at a constant rate, and when the trigger is released the flow stops. Double-action airbrushes allow for more control; as the paint's flow rate can be controlled by the trigger, allowing for gradual fade effects and blending. Double-action airbrushes are used by artists, body shops, makeup artists, photo editors and other users who need precise control of the paint coating.
Airbrushes can also be classified as siphon-feed or gravity-feed. Siphon-feed airbrushes hold the paint canister on the bottom, which allows for the possibility of using a larger container but means you have less precision and balance. Gravity-feed airbrushes hold the paint reservoir on the top of the airbrush body, allowing greater precision and balance. However, gravity-feed airbrushes are typically incapable of holding a large amount of paint and are used mostly for detail work.
Lastly, airbrushes are classified by the location of the mixing point of the paint and air. Internal mix airbrushes mix the air with the paint in the tip of the tool, allowing for a greater atomization effect which in turn produces smaller paint droplets. External-mix airbrushes introduce the paint stream after the tool's nozzle, which creates larger paint droplets; this type of brush is more suitable for paint coating than detailed airbrushing.
Most airbrush artists use several common techniques, which are then expanded to create interesting visual effects and develop advanced detailing techniques. Basic airbrush technique involves making sure that the brush is constantly moving to avoid pooling or heavy paint spots. The artist's hand should always begin moving before the paint flow is applied; on double-action airbrushes, the artist should always begin paint strokes with a jet of pure air, then introduce paint to the flow when the brush is at the correct spot.
Double-action airbrushes are also capable of performing the basic "dagger stroke" technique, which involves steadily increasing the paint flow during a line while moving the airbrush tip gradually farther from the surface of the medium. If performed correctly, this should result in a line which gradually widens from a point; this stroke can also be performed in reverse, gradually decreasing flow while moving the tip closer to the medium to bring the line to a point.
Fading techniques can be performed by altering the brush's distance from the surface without changing the paint flow rate, or by angling the airbrush while applying paint. Fine-detail techniques can be performed with the use of a stencil or masking film.