The action type refers to the trigger mechanism, and the trigger mechanism controls how air and paint/dye/etc. is released from the airbrush. Single action triggers control the flow of air from the airbrush, while flow and spray are adjusted via manual adjustments separate from the trigger. Dual/Double action triggers allow for simultaneous adjustment of air and fluid via the manipulation of the trigger mechanism.
Beyond the trigger mechanism, there is the feed type, which are:
The feed types should be pretty self explanatory, but their use may not…
Gravity Feed pulls the fluid from a reservoir sitting above the airbrush. Bottom Feed and Side Feed siphons the paint/dye from a reservoir mounted below (Bottom Feed) or on the side (Side Feed) of the airbrush.
Gravity Feed airbrushes typically provide the finest spray, resulting in higher possible detail in your work. However, they don’t typically hold as much fluid, so these are better suited for detail work.
Bottom/Side Feed airbrushes provide better visibility of the work since the fluid container isn’t obstructing the view. They also typically hold a larger capacity of fluid, so these are better for large coverage areas.
What do I use?
When I was studying Communication Design (Advertising Art) in college, I purchased a Badger 150 from the local hobby store. That was sometime around 1995. It’s the only airbrush I own (unless you count my much larger paint sprayer that functions the same way…). It’s a Double Action, Bottom Feed airbrush, and it works perfectly fine for my needs.
Many people are perfectly fine with the much less expensive airbrushes from Harbor Freight and they’ve used them for years. I’ve never personally researched their offerings, but encourage you to do so if you’re in the market for a new airbrush. The cost of airbrushes vary greatly and you don’t need to spend a lot if all you’re planning to do is dye some leather. If you’re planning on airbrushing flames on a vehicle, that’s another story and I highly recommend you seek out a related message board for more information on what to buy.
What can I spray through an airbrush?
Anything as thick or thinner than milk can be sprayed through an airbrush. Some people spray liquids such as oils through their brush, but I’m not sure if they warm the oil first to lower the viscosity. Thick paints can be sprayed as well, but you’ll need to dilute it with the appropriate thinning agent before spraying it through the airbrush.
How big of an air compressor do I need?
You only need about 30+/- psi of air pressure to operate an airbrush. Some people recommend a little more, others less. I set my regulator gauge on my compressor to about 35 psi. When I press the trigger on my airbrush, the line pressure drops to about 30 psi, which works well for me. I’m sure there is a “rule of thumb” for what pressure to use for various situations, but I’m not aware of any specifics.
For more information on airbrushes, check out the Wikipedia article below: http://en.wikipedia.org/wiki/Airbrush