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Additional Materials Problems – Fluttering Spray and its Kin

Some materials problems are even more serious than those which were just described; these hindrances can prevent the paint gun from working at all until they are addressed, or cause such huge flaws in the paint application that the spray gun might as well be non-functional.

If the spray comes out in a “fluttering” manner – difficult to describe, but unmistakable when seen – then a whole laundry list of causes could be at the root of this effect. The material might be too viscous for the nozzle you are using, and is thus being forced through in spurts rather in a steady stream – in this case, the “cure” is to either thin the material or use a larger nozzle. Alternatively, partial blocking of the vent port in the paint cup, where air is drawn in from the outside, might be responsible, and this should be cleaned out if any obstruction is visible.

Fluttering spray can result from low amounts of paint remaining in the cup, which is corrected, naturally, by refilling this reservoir. Loose needle packing can prompt a flutter in the spray, so the packing nut should be tightened and, if this fails to work, the packing itself replaced. An air leak can also be the cause of fluttering, and this should be checked for and corrected with either tightening or Teflon tape as described in the article on the subject.

If the paint, primer, or other material refuses to come out of the gun at all, or does so very feebly, then the prime suspect is a clogged nozzle. Remove the air cap and then the nozzle, and clean it thoroughly with solvent. Alternatively, check the fluid pickup tube inside the paint cup for clogging and clean it if necessary, and make certain that the air vent in the cup’s top is open.

A problem unique to gravity-feed spray guns mounting the paint cup above the nozzle is the paint bubbling inside the cup, which throws off its usual properties. The cause is a loose nozzle – remove the air cap to tighten the nozzle, then replace the air cap and resume shooting.


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