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Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2005

Orange Peel Paint Defect with HVLP Spray Gun

Q. I am trying to spray my truck but can't get rid of the orange peel effect. I am using an HVLP gravity feed gun. I am spraying with NASON Urethane paint. The paint calls for 8-parts paint 1-part catalyst and 2-parts reducer. I am spraying at 10 lbs pressure. I have heard a couple of different ways to possibly eliminate the problem but nothing has worked yet. I could really use your advice. Thanks .

A. You are probably using way too little air pressure. I assume that when you say that the atomizing pressure is 10 lbs you are referring to the pressure that you read on the pressure gauge at the handle of the spray gun? Well, if that it so then I'm not surprised that you are getting orange peel. I don't know which HVLP spray gun you are using, but you are permitted to increase the atomizing pressure so that it reads 10 lbs per square inch (psig) at the CAP of the gun ... not at the handle. Special pressure gauges can be purchased from the spray gun vendor to measure the pressure at the CAP. If you refer to the spray gun manual it will tell you what the maximum pressure is at the handle of the gun to give you 10 psig at the cap.

By increasing the at atomizing pressure without increasing the fluid (paint) flow rate, you will significantly improve the finish. On the other hand, if you over atomize the paint you will get dry spray, so I suggest that you experiment with the air pressure until you get the best atomization.

By the way, within the next few weeks I will be selling a CD that provides step by step methods for setting up an HVLP spray gun.


Ron Joseph

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