External vs. Internal MixingAirbrushes work by mixing air with liquid (such as paint or glaze) so that the paint is applied in a light, even layer. Air is supplied via a compressor or with cans of compressed air (for short spurts of painting). The liquid (usually paint) is in a bottle or jar attached to the airbrush.
With single action airbrushes the mixing of paint and air occurs externally, outside the tip. They are less likely to clog when using heavier paints. In (most) double-action systems the air and liquid are mixed inside the airbrush. The liquid may need to be thinned more to prevent clogging but this internal mixing produces a finer spray of paint than external mixing.
Single-Action AirbrushThe basic model airbrush systems are usually single action and generally less expensive. The paint comes out at a pre-set rate when you press the trigger. Release the trigger and the paint flow stops. Single-action airbrushes tend to have the least amount of control of air flow and volume of paint dispensed at a specific time or amount. However, they are perfectly suitable for a wide range of applications (including painting RC vehicle bodies) such as crafts, murals, and using stencils.
Double-Action AirbrushDual-action airbrushes have a trigger system that provide the user with much more control over paint flow. The trigger system has separate controls over both air and paint amount to be mixed before they are dispensed. It allows for greater control of the width of the spray of paint, opacity and gradation, and provides a finer spray.
The double-action airbrush is more commonly used by intermediate to expert artists but this doesn't exclude the beginner. They allow for greater precision detail work. Double-action airbrushes also are usually more pricey than the single-action basic airbrush.
Find Single-Action Airbrushes
Single Action Airbrushes from Paasche.
Badger Model 350 Single Action Airbrush at Blick Art Supplies.
Find Double-Action Airbrushes
Double Action Airbrushes from Paasche.
Badger Model 150 Double Action Airbrush at Blick Art Supplies.