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Proper attention to detail, as you switch from spraying one finish to another, is a great way to avoid finish incompatibility problems.
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The devil is in the details, or so they say, and that’s true for finishing, too. Sometimes, it’s the little things that trip you up: things like a clean spray gun.
We all know that spraying through a dirty gun can contaminate our finishes. Droplets of incompatible solvents can create spots or “fish-eyes” where the finish refuses to flow out smoothly. Bits of old dried finish cause annoying globs of dirt to mar the beauty of what we spray. I’m not going to lecture you about good cleaning habits. That was your mother’s task. Instead, I’ll give you a few tips that will make gun cleaning easier, and a nice little trick that often allows you to skip the arduous cleaning ritual altogether. (See “A Complete Washout,” below.)
Dismantling and Soaking
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| Remove and soak, from left to right, the air cap, fluid tip, gasket ring, fluid needle, spring, and control knob. Scrub the fluid passageways of the gun with solvent and a bottle brush. |
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The first step after spraying is to pour out any remaining finish, then flush the gun by spraying a few ounces of the finish’s solvent through it. Now pour some of the solvent for the finish in a pan and use it to soak the small parts and scrub the large ones. The photo (above right) shows the parts to be removed in the relative position they occupy in the gun. Remove the air cap, fluid tip, gasket ring, fluid needle, spring, and control knob. Soak them in solvent, then scrub with a small brush to be sure they are clean, and that no holes in the fluid tip or air cap are blocked. Be especially careful with the gasket ring — it’s easy to lose. Not all guns have one, but those that do won’t spray without it.
Scrubbing and Reassembling
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Use a Q-tip® to apply a small amount of petroleum jelly to all the threaded parts
of the gun before you reassemble. This keeps them moving freely and easy to disassemble next time you clean. |
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Don’t soak the gun body. It contains packing material, just behind the fluid tip, that can be destroyed by some solvents. Instead, scrub the fluid passageways, those areas that finish flows through, with solvent and a bottle brush. Before I reassemble the gun, I apply a bit of petroleum jelly on all the threads. That keeps them turning smoothly and makes it easier to disassemble everything for the next cleaning. Finally, make sure the fluid tip seats very snugly when you screw it back in or it will cause the gun to spit.