How to Troubleshoot a Spray Gun
Learn to handle the typical problems and enjoy carefree spray-finishing
Synopsis: When everything works correctly, a spray gun delivers a thin, even coating of finish that makes furniture look fantastic. But what to do when everything is not working correctly? Learn how to troubleshoot common spraying problems by analyzing the spray pattern. Once you’ve learned to diagnose and correct the typical problems, your spray finishing will be trouble-free.
As the technical troubleshooter for my business, I’ve been asked to solve just about every spray-gun problem imaginable, from a new gun that just hisses air to an old gun that used to spray perfectly and now leaves a horrible finish. The good news is that in most cases, you can diagnose the cause of the problem by analyzing the spray pattern. In a few other situations, a slight change in your spraying technique can help. Even if you’re just considering taking the leap into spray finishing, knowing how to achieve and maintain a good spray pattern will give you the confidence you need.
Since all spray guns operate on the same basic principle, it doesn’t matter whether you have a high-volume, low-pressure (HVLP) gun or a non-HVLP gun, a turbine-driven system or a compressor-driven system. When differences exist, I’ll call them out.
Most of the time some finish comes out of the gun, just not in a manner to give that thin, even coating that makes spraying so worthwhile. One of the most common problems is uneven coverage, which leaves a repeating light/dark effect when the finish dries. You can study the spray pattern with a light shining through it. If you find this difficult, spray some dark finish or stain onto cardboard. If you substitute a dark finish for a clear one just to test the pattern, be sure that it has a comparable viscosity.