Testing your Spray Gun’s Pattern

Although handwriting analysis frequently fails to yield any useful results when applied to human beings – with only the most tortured explanations actually matching a person’s handwriting to the supposed personality traits allegedly revealed by this method – examining your spray gun’s “John Hancock” for revelatory information is much more straightforward.

Indeed, test-spraying is an extremely fruitful way of detecting problems with either air or paint flow, and should be carried out before every major paint job. Some painters also shoot a test pattern periodically during a long, thorough paint job, using a piece of masked paper tacked up on the wall of their workspace as a testing surface. If you are painting an entire car, you should, at a minimum, test the spray pattern every time you fill the paint cup.

To test spray, set up your spray gun, filling the paint cup three-quarters of the way as usual, and connect the paint gun to the compressor. Set up a piece of clean paper or white cardboard in a vertical position, tacking it in place if necessary, at a height where you can spray it most conveniently – probably at about waist height, since holding your upper arm straight down at your side and your forearm out at right angles to your body is the most stable way to aim your paint gun.

Place the air cap around 8 inches (or 4 inches, if you are using a low-pressure gun, either high-volume or low-volume) from the paper’s surface. Then give a single rapid trigger-pull, opening the trigger fully and then immediately letting it snap shut, shooting a concentrated burst onto the paper or cardboard. Observe the spray pattern produced. If the spray pattern is a long, narrow, upright oval, then the spray gun’s parts are all properly adjusted and you can commence spraying.

However, you may encounter one of a number of different incorrect spray patterns. Each of these will reveal a distinct problem with the implement, requiring specific measures to correct it. Keep some brushes, solvents, and specialized air-gun lubricants on hand to deal with any problems, as well as a few wooden toothpicks (metal being too risky for reaming out air orifices) and whatever tools are necessary to disassemble your specific model of paint gun. Being prepared will save you much time in the long run.