Airbrush Types Explained: Dual vs Single Action, Gravity vs Siphon Feed

Action: dual or single

Dual action. Press the trigger down for air, pull it back for paint; pull further for more paint. Iwata says nearly all its airbrushes work this way. Because you control the paint as you spray, you can start a line thin, widen it and fade it out in one stroke. This is what tutorials teach, and what you want for shading, gradients, models, miniatures and illustration.

Single action. The trigger controls only the air. A dial or set screw sets how much paint flows, and it stays fixed while you spray. Iwata's Revolution SAR and Paasche's H are examples. Single action is easier to learn and gives repeatable coverage, which suits even coats on crafts, cakes and ceramics, but you cannot vary a line mid-stroke.

Feed: gravity, siphon or side

Feed	Where the paint sits	Pressure	Best for
Gravity	A cup on top	Lowest: gravity helps the paint flow	Detail, small amounts, quick color changes
Siphon (bottom or bottle feed)	A jar or bottle underneath	Higher: the air has to lift the paint	Large areas, fabric, long runs of one color
Side	A cup or bottle on either side	In between	Clear sight line over the airbrush; left or right-handed setups

Iwata's basics page gives the reasoning: gravity feed sprays at lower pressure and uses little paint, while siphon feed needs more pressure because the compressor does all the work, and suits larger amounts. Iwata's own figures show it. The gravity-feed Eclipse HP-CS has an optimal working pressure of 25 to 35 psi; the siphon-feed Eclipse HP-BCS, otherwise the same family, is rated 35 to 55 psi and takes a 2 oz (60 ml) bottle.

Harder & Steenbeck makes suction (siphon) versions of its main models (the Evolution X and Ultra X), and Paasche's VL is a siphon airbrush that takes bottles from 1/4 oz to 8 oz.

Mix: internal or external

In an internal-mix airbrush, air and paint meet inside the head and leave as a fine mist. In an external-mix airbrush, they leave through separate openings and mix in the air. Iwata says external mix is sometimes easier to clean but gives coarser atomization and less even patterns; all Iwata airbrushes are internal mix. Paasche's H is the classic external-mix model: simple, cheap and easy to clean, and Paasche rates it from 1/16 inch lines to 1-1/2 inch patterns.

Nozzle size

The nozzle (and its matching needle) sets the finest line and the thickest paint an airbrush will pass. Makers sell the same body with different heads:

Nozzle	Typical use	Examples
0.15 to 0.25 mm	Fine detail, freehand, faces on miniatures	H&S Infinity 2024 (0.25 mm titanium), Gaahleri Mobius 0.2 mm
0.3 to 0.38 mm	General hobby and craft spraying	Iwata Eclipse E3 (0.35 mm per Iwata's nozzle listing), Paasche Talon TG#2 (0.38 mm)
0.4 to 0.5 mm	Primer, varnish, metallics, base coats	H&S Evolution and Ultra 2024 (0.45 mm), Master G233 (0.5 mm set)
0.6 mm and up	Fabric paint, large areas, thick media	Paasche VL size 3 (0.75 mm), H&S Evolution X Two in One (0.6 mm set)

Smaller nozzles need thinner paint and clog sooner; larger ones forgive thicker paint but cannot draw a hairline. Two-nozzle airbrushes such as the H&S Infinity 2in1 or the Gaahleri GHAD-39 let you cover both ends.

Nozzle fitting

• Screw-in (threaded): the most common. Tighten gently; over-tightening cracks the nozzle.
• Compression fit: Iwata's Eclipse nozzle is clamped by the head cap, with no threads. Iwata says it is easy to install and clean and handles thicker material without clogging.
• Self-centering drop-in: H&S and Gaahleri use nozzles that seat themselves when the head is assembled, and strip without tools.

Other features worth knowing

• Trigger-style airbrushes. Iwata's HP-TH and NEO TRN1 use a pistol-style trigger instead of a top lever. Iwata says they suit painters used to spray guns and people with arthritis; they are still dual action.
• Micro air control (MAC) valve. A small valve on the airbrush itself that fine-tunes airflow for fine to medium spray and stipple effects. Iwata fits one to all its Hi-Line models.
• Cutaway handle. An open back that exposes the needle chucking nut so you can pull the needle back to flush the airbrush without removing the handle (Iwata's Eclipse HP-CS has one).
• Preset handle. A dial at the back that limits how far the trigger travels, so you can repeat the same line width; Harder & Steenbeck's Infinity has a Quick Fix end piece with an engraved scale for the same job.
• Solvent-resistant seals. Needed for lacquers and urethanes: H&S fits PTFE seals and Paasche PTFE packing to their airbrushes.

Which type to buy

You paint	Buy
Models, miniatures, illustration	Dual action, gravity feed, 0.2 to 0.35 mm
First airbrush, mixed hobbies	Dual action, gravity feed, 0.3 to 0.45 mm
T-shirts, fabric, large boards	Dual action, siphon feed, 0.5 mm and up
Cakes, cookies, even single-color coats	Single or dual action, gravity feed
Simple coverage on a budget	Single action, external mix

Ready to choose a model? See the best airbrush kits, the best airbrush for beginners and airbrushes for t-shirts.