Blue spray gun with red panel in the background and close up of adjusting spray gun

November 2014

The air pressure of your spray gun matters. It would be difficult to argue against that. But do you know how low pressure versus high pressure affects the performance of your coating?

 

Low Pressure

 

The typical issue with air pressure set lower than the manufacturer’s recommendation is poor atomization, or the separation of paint particles. Poor atomization can lead to a higher film build than desired, because the particles are too large when they hit the substrate. Depending on the severity of the increased film build, the coating dry time could slow and there could be a loss of gloss, solvent entrapment or popping.  

 

Poor atomization also can lead to noticeable texturing of the coating.   

 

High Pressure

 

As you would expect, air pressure set higher than the manufacturer’s recommendation can lead to problems at the other end of the spectrum – low film build, excessive overspray, and even poor metallic control. Higher air pressure normally will "split" the fan pattern where the middle is very light and the ends are heavy (called tails). The inconsistency of the spray will cause streaking and provide little metallic control. Not only will the control of the spray be compromised reducing paint transfer and increasing waste, but lower film build can sacrifice the durability of the paint system.  

 

How often have you or your painters observed these problems? Not only that, but how long did it take for you to identify the root cause of the issue? Besides issues with high and low air pressure, it is critical where you measure that pressure. Some guns come with pressure gauges integrated in the handle and some come with a gauge you can attach at the base of the gun. That is where you want to measure pressure - not at the wall where the airline enters the booth. The measurement at the wall will be higher than what actually makes it to the gun.  

 

Now that you understand the importance of finding the air pressure that matches your painting style, fits with the product you are using, and falls within the range of the manufacturer’s recommendation, you have a starting point for self-diagnosing your coating problems.

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