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Ask the Expert Question-and-Answer Archive

by Ron Joseph

June, 2008

Paint Streaks

Q: I have been having a problem with streaking from my airless spray gun. When you look at the wall at different angles, it is almost like the wall is absorbing the paint in some places. The drywallers have sealed it and I have PVA on the walls and then the color. I have looked at the wall very close and it seems that there are places that the paint seems to be sharper on the drywall texture and places where it has smoothed in better. Looking straight in at the wall, you can not see any difference, it is only at angles. We are using a graco spay gun and machine. I have a 415 tip in there now. I know that the 15 is a bit on the small side for a latex paint but still in range, also I have played with the pressure setting on the machine and I have had no luck with that. I have tried different overlaps (normally I do about a 50% over lap). Any help you could offer to get rid of these stupid streaks would but greatly appreciated.

A: Have you tried spraying a large sheet of metal or a large piece of aluminum foil that you can purchase from a supermarket? In my opinion, your first approach should be to rule out the effect of the substrate as the cause for streaking. Perhaps even purchase a large piece of drywall and test it for differential absorption o the paint.

My first guess is that you are getting an uneven pattern from your spray gun. This can be due to the narrow fan, but it can also be due to low fluid pressure. The narrower the fan, the sharper the edges and the more difficult it is to get a uniform pattern. I would try to increase the fluid pressure to achieve better atomization, and if possible increase the fan with by using a 10" rather than an 8" fan (you are using a 415 tip).

Good luck,

Ron Joseph

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