A.k.a.: Pete S
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Mad fabricator, paint and body
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Registered: September 1st, 2002
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posted on January 3rd, 2006 at 09:43 AM
More spraypainting tips for you
So many paint questions, I will post anything I find on the net that should help.
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Correct air pressure and how it can aid in better spray painting.
Correct air pressure is essential if you want to get a fine finsh on those special painting projects without losing too much paint in the process.
The term high-pressure spray gun does not mean that the pressure has to be high, it means that the material is syphon fed, and the pot is vented.
(With a low pressure spray gun the material is forced out of the pot under pressure and the pot is not vented.)
The most crutial parts of a spray gun are the air cap, fluid nozzle and fluid needle, so take extra care of these parts.
How the Air Cap Works
1. The centre hole generates a vacuum and syphons the paint.
2. The side holes on the horn adjust the spray pattern.
3. The auxilliary holes prevent paint from adhering to the air cap and assist in atomisation.
Spray Painting 101 (A Quick Guide)
High pressure spray guns are designed to run at between 45 and 55 psi (while the gun is running). Low pressure spray guns run at 10 to 50 psi.
Pressure: If the air pressure is too low paint won’t atomise properly. If the air pressure is too high, paint loss is high, and too much overspray
results.
Spraying Distance: The distance from the work that spraying occurs is also critical to a good finish and the level of paint loss. If you are too close
to the work the paint will ripple (orange peel). If you are too far from the work, problems include high paint loss, overspray, and rapid drying
(resulting in inconsistencies in the paint finish). The ideal distance is approximately 8 inches from the work. Also critical to the finish is the
thinners-to-paint ratio.
At 45 psi - paint loss is 46%.
At 75 psi - paint loss is 77%.
At 8 inches spray distance - 77% of the paint sticks to the job.
At 12 inches spray distance - 67% of the paint sticks to the job.
