Double action refers to how you work the airbrush. A double action airbrush combines two seperate motions into a single control, the trigger.
Like the picture shows.
Press down for air
Tip: Don’t try to control the air pressure here, that’s what air regulators are for. The up and down motion controls the air flow. It’s an on/off motion.
Pull back for paint
The back and forth motion controls the amount of paint introduced into the air stream.
Double action airbrushes are also commonly refered to as dual action airbrushes.
Easy to control paint flow.
Double action airbrushes, through the trigger, allow you to easily control the amount of paint introduced into the air stream.
This variable control allows you to paint dagger strokes.
Promotes Good Airbrush Technique.
I sum up good airbrush technique this way.
In other words, good airbrush technique is part of how you should spray. Single action airbrushes can’t do this so well.
The more ‘things’ you have to control or ‘keep in mind’ the harder it is to learn. The control allows advanced techniques, but it’s an added variable that takes longer to learn while causing more frustration.
Most paints sprayed through airbrushes are not completely uniform. Paint consistency changes from moment to moment. Most of the time these changes aren’t big enough to worry anyone, especially beginners. But photo-realists, and fine artists should be aware that paint doesn’t always flow the same from moment to moment. You can develop a ‘feel’ for how the paint flows and sprays through the airbrush, but it takes time and patience.
Most people should choose double action airbrushes. There are a few extra headaches to overcome but it’s worth it. As an added bonus, if you know how to use dual action airbrushes, single action airbrushes are really easy.
If you’re a scientist or researcher you’ll probably want to go with a single action airbrush.