Why is my airbrush spitting, clogging or spraying nothing?

An airbrush has very few parts and a passage through the nozzle narrower than a hair, so almost everything that goes wrong is either something in that passage or something about how the paint reaches it. Diagnosing it by spraying a test card and reading the pattern is far faster than changing the thinning and hoping.

Safety

What you'll need

• Airbrush cleaner appropriate to the paint
• Interdental brushes or a nozzle cleaning kit
• Wooden cocktail sticks — never a metal pin
• A moisture trap for the air line (optional)
• Scrap card for test passes

Step by step

1. Spray a test pass on scrap card and look at the pattern.This is the diagnosis. A soft even fan is right. Blobs and stuttering, radiating legs from a wet centre, a fine dusty speckle, or nothing at all are four separate faults with four separate causes.
2. Deal with spatter and pulsing first, because it is usually the nozzle.Dried paint in the nozzle bore or around the needle seat interrupts the flow. Strip the front end, soak the nozzle in the appropriate cleaner, and clear it with an interdental brush and a wooden stick. Never a drill bit or a pin — the nozzle is softer than steel and the bore will be reshaped permanently.
3. Check the nozzle is seated and tight.A nozzle that is loose, cross-threaded or has a damaged sealing face lets air leak into the paint path, which produces exactly the same stuttering. Hand tight and no more; over-tightening splits it.
4. Fit a moisture trap if you have not.A compressor pumps warm moist air, and it condenses in the line and arrives as periodic droplets that blow the paint into blobs. The pattern looks like a nozzle fault and no amount of cleaning helps. A trap at the airbrush end is more effective than one at the compressor.
5. Fix spidering by backing off, not by thickening.Radiating legs mean too much wet paint arriving in one spot. Move further back, pull the trigger less far, and keep moving. Start the movement before the trigger goes back and finish it after the trigger returns.
6. Fix grain by moving closer and dropping the pressure.A dusty speckled pattern means the droplets are drying in flight. Closer, lower pressure, and a little retarder in the paint fixes it. A hot dry room makes it much worse.
7. Trace no flow at all in order.Air but no paint: check the trigger is actually being pulled back, that the needle is not stuck forward in the nozzle, that the cup is not blocked at the outlet, and that the paint is not too thick. No air either: check the compressor, the hose connection and the tank pressure.
8. Wipe tip dry between passes.A crust building on the needle tip deflects the spray to one side and then blocks it. A cotton bud damped in cleaner, wiped over the tip, takes two seconds. Adding flow improver reduces how often you need to.

Tips

• Strain paint through a fine mesh or a piece of old tights before it goes in the cup. Most sudden blockages are a fleck of skinned paint, not a dirty airbrush.
• Keep a spare nozzle and needle for your airbrush. They are the parts that wear and get damaged, and a session ends the moment one bends.
• If the pattern is fine on card and bad on the model, the problem is technique or distance, not the airbrush.

Common mistakes

• Poking a metal pin or drill down the nozzle — Brass and steel nozzles are softer than the tool. One pass reshapes the bore, and the airbrush never sprays evenly again. Wooden sticks and solvent only.
• Pushing the needle forwards out through the nozzle — It splits the nozzle or bends the needle tip, and a bent tip gives a permanently lopsided pattern. The needle always comes backwards out of the rear of the body.
• Assuming every fault is thinning — Thinning causes two of the four patterns. Changing the mix to fix a blocked nozzle wastes paint and time, and over-thinning to compensate creates a second problem on top of the first.

If it doesn't work

Questions people ask