Model Train Resources - AirBrush Trouble Shooting

If your airbrushing experiences are trouble-free, you are blessed. Even with years of experience, many modelers still have problems with their airbrushes. While the following is by no means complete, solving (or avoiding) these common problems will help a lot.

Paint creeping out in a spidery star pattern is an indication of too much of everything: paint volume, thinner, time spent spraying one spot, too close to the surface, and so forth. First, close the paint nozzle until paint barely comes out while you spray. While pressing the air control button, slowly move the airbrush toward the test model. (You are using an unwanted test model, aren’t you?) If you close in to where you’re producing a small dot of paint but it is still "spidering," your paint is too thin, you have too much air pressure, or both.

Reduce the air pressure (if you can), add paint to the mixture, and adjust the paint nozzle until those arachnids disappear. Make note of paint-to-thinner ratios, air-pressure settings, and the distance from the surface you’re spraying so you can avoid this problem in the future.

This is usually the result of paint that’s not thinned enough or is nearly dry when it hits the model’s surface. When paint dries this fast, it clumps on the surface. Back off the air pressure and check the paint-to-thinner ratio. Properly airbrushed paint should go on slightly wet, and if you’re using a flat paint, the sheen should disappear in a few seconds.

To improve paint flow, add a few drops of Floquil Glaze (for enamels) or a clear gloss (for water-based acrylics) to the paint/thinner mixture. This will help keep the paint from drying too quickly or clogging the airbrush tip.

If you get puddles or runs, you’re allowing too much paint to come out of the nozzle or you’re not moving the airbrush and the paint is piling up in one spot. Keep the airbrush moving or cut back on the amount of paint in your paint/thinner mixture.

You don’t need to blast paint on the model and cover it with one pass. If clouds of overspray form, you’re applying too much paint with too much air pressure. Reduce the air pressure to 10 or 15 psi – that’s all you really need for properly thinned model paints.

The other overspray problem is not as easily solved. If you’re painting a thin line but notice a spattering to one side of the pattern, the cause is likely a damaged paint nozzle. Whether you’re using a single- or a double-action airbrush, either the needle (tip) or the nozzle (paint cap) can be the culprit. Disassemble the airbrush to fix it. Use a magnifying glass and inspect the needle. Does it have a hook? You may have dropped or bumped the airbrush and bent the tip of the needle.

Sometimes you won’t be able to see the bent tip. In this instance, draw the tip of the needle backward lightly across your fingertip – be careful, it’s sharp! Rotate the needle 90 degrees and draw it over your finger again. Does it feel the same? Rotate again and you’ll get a sense that one side of the needle drags on your finger more than the rest. Determine which side of the tip is hooked and lightly draw that side along 600-grit sandpaper or a medium-grit sanding stick. Just make one pass, then test it on your finger again. Test and repeat until the tip of the needle feels smooth all around.

The nozzle could be cracked, too. Use the magnifier to look for a ragged opening or a crack down the side. If the nozzle is cracked, replace it.

Is the paint nozzle opening? If yes, then there is a clog somewhere behind the nozzle. Remove the paint cup or bottle and watch for drips. If you can’t see paint at the end of the siphon connector, the clog may be in the siphon. Perhaps large chunks of pigment can’t travel up the siphon tube. Empty the paint from the cup/bottle and clean the tube with lacquer thinner and a pipe cleaner. You may have to strain the paint to filter out the big chunks.

If the paint nozzle is not opening (when you pull the button back on a double-action airbrush), the needle is stuck in the nozzle and the locknut is slipping. On a standard double-action airbrush, unscrew the handle and remove it. Tighten the needle locknut and try pulling the button back. The needle should travel back with the button.