History

The airbrush was later improved by Peeler which used a hand-operated compressor, and the inventor patented it "for the painting of watercolors and other artistic purposes". It was rather crude, being based on a number of spare parts in a jeweller's workshop such as old screwdrivers and welding torches. It took 4 years of further development before a practical device was developed. This was marketed by Liberty Walkup, who taught airbrush technique to American Impressionist master Wilson Irvine. The first modern type airbrush came along in 1893, presented by Thayer and Chandler art materials company at the World Columbian Exposition in Chicago, invented by Charles Burdick. This device looked like a pen and worked in a different manner to Peeler's device, being essentially the same as a modern airbrush. Aerograph, Burdick's original company, still makes and sells airbrushes in England.

For more a detailed academic study, the University of Wales Library holds a detailed PhD on Airbrush History. Likewise the Franklin Institute in Philadelphia retains a copy - authored by Dr. Andy Penaluna.

Design

An airbrush works by passing a stream of fast moving (compressed) air through a venturi, which creates a local reduction in air pressure (suction) that allows paint to be pulled up from an interconnected reservoir at normal atmospheric pressure. The high velocity of the air atomizes the paint into very tiny droplets as it blows past a very fine paint-metering component. The paint is carried onto paper or other surface. The operator controls the amount of paint using a variable trigger which opens more or less a very fine tapered needle that is the control element of the paint-metering component. An extremely fine degree of atomization is what allows an artist to create such smooth blending effects using the airbrush.

The technique allows for the blending of two or more colors in a seamless way, with one color slowly becoming another color. Freehand airbrushed images, without the aid of stencils or friskets, have a floating quality, with softly defined edges between colors, and between foreground and background colors. A well skilled airbrush artist can produce paintings of photographic realism or can simulate almost any painting medium. Painting at this skill level involves supplementary tools, such as masks and friskets, and very careful planning.

Some airbrushes use pressures as low as 20 psi (1.38 bar) while others use pressures in the region of 30-35 psi (2-2.4 bar). Larger "spray guns" as used for automobile spray-painting need 100 psi (6.8 bar) or more to adequately atomise a thicker paint using less solvent. They are capable of delivering a heavier coating more rapidly over a wide area. However certain spray guns called, High-Volume Low-Pressure (HVLP) spray guns, are designed to deliver the same high volumes of paint without requiring such high pressures.

Types

Airbrushes are usually classified by three characteristics. The first characteristic is the action performed by the user to trigger the paint flow while the second is the mechanism for feeding the paint into the airbrush and the third is the point at which the paint and air mixes.

Trigger

The simplest airbrushes work with a single action mechanism where the depression of a single "trigger" results in paint and air flowing into the airbrush body and the atomized paint being expelled onto the target surface. Cheaper airbrushes and spray guns tend to be of this type.

Dual action or double action airbrushes separate the function for air and paint flow so that the user can control the volume of airflow and the concentration of paintflow through two independent mechanisms. This allows for greater control and a wider variety of artistic effects. This type of airbrush is more complicated in design than single action airbrushes which tends to be reflected in its cost.

Feed system

Paint can be fed by gravity from a paint reservoir sitting atop the airbrush (called gravity feed) or siphoned from a reservoir mounted below (bottom feed) or on the side (side feed). Each feed type carries unique advantages. Gravity feed instruments require less air pressure for suction as the gravity pulls the paint into the mixing chamber. Typically instruments with the finest mist atomization and detail requirements use this method. Side- and bottom-feed instruments allow the artist to see over the top, with the former sometimes offering left-handed and right-handed options to suit the artist. A bottom feed airbrush typically holds a larger capacity of paint than the other types, and is often preferable for larger scale work such as automotive applications and tee-shirt design.

Mix point

With an internal mix airbrush the paint and air mixes inside the airbrush (in the tip) creating a finer atomized "mist" of paint. With external mix the air leaves the airbrush before it comes into contact with the paint which creates a coarser stippled effect. External mix airbrushes are cheaper and more suited for covering larger areas with more viscous paints or varnishes.

Spray guns

The airbrush led to the development of the spray gun; a similar device, that typically delivers a higher volume of paint and is configured with a pistol grip to facilitate painting larger areas.

Technique

Airbrush technique is the freehand manipulation of the airbrush, medium, air pressure and distance from the surface being sprayed in order to produce a certain predictable result on a consistent basis with or without shields or stencils. Airbrush technique will differ with the type of airbrush being used (single action or dual/double action).

Double action airbrush technique involves depressing the trigger on the top of the airbrush with the index finger to release air only, and drawing it back gradually to the paint release threshold. The most important procedural dynamic is to always begin with air only and end with air only. By observing this rule, precise control of paint volume and line width and character can be achieved. The single most important airbrush stroke consistently utilized by professionals is the dagger stroke. This describes a stroke which begins wide and ends as a narrow line, created by starting with the brush far from the support and moving it evenly closer as the line is drawn.

Single action airbrush technique derives its name from the fact that only 1 action is required for operation. The single action of depressing the trigger releases a fixed ratio of paint to air. Achieving different line widths requires either changing the tip and nozzle combination or else adjusting the spray volume manually between spray width changes. The most important aspect of proper single action airbrush technique is to keep the hand moving before the trigger is depressed and after the trigger is released. This avoids the "bar bell" line.