Here’s How to Fix a Spray Pattern that is Heavier on One End - Popular Woodworking Magazine
 In Flexner On Finishing, Flexner on Finishing Blog

You can check the quality of your spray gun’s spray pattern by triggering a short burst onto cardboard.

A spray pattern, with all the controls on the spray gun wide open, is supposed to be an even, elongated oval shape. If the pattern is heavier on one end than the other, the likely cause is that one or more of the holes in the air cap are plugged up. It’s also possible that the fluid nozzle has been damaged.

To determine which, rotate the air cap one-half turn (180 degrees) and spray again. If the disrupted pattern switches sides, the problem is in the air cap. If the pattern stays the same, the problem is the fluid nozzle.

To clean the air cap, soak it in acetone or lacquer thinner to dissolve or soften the obstructing matter, then blow it out with compressed air if you have it. You can also use very small-diameter picks supplied with spray-gun cleaning kits that often come with the spray gun. Spray Gun Solutions, Inc. (http://sgskits.com) sells several kits of different sizes.

Be very careful if you try using a toothpick, because it might break off in the hole and be difficult to remove. Above all, you don’t want to use any metal so hard that it might damage the hole.

If you determine that the fluid nozzle has been damaged, you will have to replace it. The fluid nozzle and needle are usually sold in sets.

– Bob Flexner

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