An airbrush turns paint into a fine mist, so you can lay down a smooth, thin coat over a whole model in seconds, prime in any weather, and make soft gradients that are very hard to do with a brush: zenithal highlights, glowing light, camouflage and smooth vehicle panels.
It is less difficult than it looks. Most problems come down to three things: how thin the paint is, how much air you use and how clean the airbrush is. This guide covers all three, for both miniatures and scale models.
| Needle | Good for |
|---|---|
| 0.2 mm | Fine detail and freehand at low pressure. Clogs more easily. |
| 0.3 mm | The all-rounder for miniatures: basecoats, zenithal, glazes and some detail. |
| 0.35 to 0.4 mm | Bigger models, vehicles and thicker paints, metallics. |
| 0.5 mm and up | Primer, varnish and big areas such as terrain. |
If you have one airbrush, a 0.3 mm or 0.35 mm needle is a good place to start.
Airbrush paint should be about the consistency of skimmed milk: it should run off the stirring stick in a smooth thin stream and coat the side of the cup in a thin, see-through film. Thicker paint clogs and spits; much thinner paint runs and pools.
| Paint | Starting point |
|---|---|
| Air ranges (made for the airbrush) | Straight from the bottle, or with a few drops of thinner. Some can be thinned a little more for fine work. |
| Ordinary brush acrylics | Roughly 1 part paint to 1 part airbrush thinner, then adjust. Many need more thinner than that. |
| Inks | Often straight from the bottle, or thinned for glazes. |
| Metallics | Thin with airbrush thinner, not water, so the flakes stay suspended. |
| Tamiya acrylics and lacquers | Thin with the maker's own thinner; Tamiya acrylics are often thinned with X-20A or a lacquer thinner. Lacquers need good ventilation. |
Thin with airbrush thinner rather than water where you can: it keeps the binder strong and dries more evenly. Add paint first and thinner second, mix in the cup with an old brush, and test on a plastic spoon or card before the model. Ranges made for the airbrush on the site:
| Brand | Range | Paints on the site |
|---|---|---|
| Citadel | Colour: Air | 44 |
| Vallejo | Model Air | 260 |
| Army Painter | Warpaints Air | 129 |
| AK Interactive | 3rd Gen Air Series | 120 |
Ordinary paints thinned for spraying are fine too: Airbrush Thinner and a drop of Flow Improver are the usual helpers.
Air pressure is measured in PSI (pounds per square inch) or bar. These are starting points, measured with the trigger pressed; every airbrush and paint is a bit different.
| Job | PSI | Bar |
|---|---|---|
| Priming and varnishing | 20 to 30 | 1.4 to 2 |
| Basecoats and zenithal on figures | 15 to 25 | 1 to 1.7 |
| Glazes, soft gradients and OSL | 10 to 15 | 0.7 to 1 |
| Fine detail, freehand and camo lines | 8 to 12, closer to the model | 0.5 to 0.8 |
Lower pressure lets you get closer and spray finer lines, but needs thinner paint. Higher pressure atomises thicker paint and covers big areas, but blows paint around and dries it before it lands. If paint spiders (runs out in little legs), lower the pressure, move back or use less paint. If it goes on rough and grainy, it is drying in the air: thin it more, raise the pressure a little or move closer.
Every so often, strip the airbrush fully and soak the metal parts (not the seals) in cleaner. Never leave paint to dry in the airbrush.
| Problem | Likely cause | Fix |
|---|---|---|
| Tip dry: paint stops, then spits | Paint drying on the needle tip. | Wipe the needle tip gently with a damp brush; add a drop of flow improver or retarder to the paint. |
| Spidering | Too much paint, too close or too much pressure. | Move back, pull less paint, lower the pressure. |
| Grainy, rough finish | Paint drying before it lands. | Thin more, move closer, or raise pressure a little. |
| Spitting or splatter | Paint too thick, dirty nozzle or moisture. | Thin more, clean the airbrush, empty the moisture trap. |
| Bubbles in the cup when spraying | Air leaking back through a loose or damaged nozzle. | Tighten the nozzle (gently) or replace it. |
| No paint at all | Clogged nozzle or needle chuck too loose. | Back-flush and clean; check the needle is seated and tight. |
Around 15 to 25 PSI for basecoats and zenithal highlights, lower (8 to 15) for glazes and fine detail, and 20 to 30 for primer and varnish. Thinner paint needs less pressure.
To about the consistency of skimmed milk. Air ranges are close to ready from the bottle; ordinary brush paints usually need at least as much airbrush thinner as paint.
A 0.3 mm or 0.35 mm needle is a good all-rounder. 0.2 mm is for fine detail; 0.5 mm for primer, varnish and big areas.
Wipe the needle tip with a damp brush now and then, add a drop of flow improver or retarder to the paint, and keep the airbrush clean.