Eliminating Fish Tails in Finish

A beginner gets advice on tip choice and fluid and air pressure settings to help optimize his spray pattern. June 18, 2013

I have a CAT AAA system. I'm still new with this gun. Right now I'm shooting with the Cougar gun 513 tip. I'm applying Mohawk Dura coat pre-cat white. First of all I can't seem to get rid of the fish tails, and second, when I'm shooting a big panel - in this case 18" x 8' - I get a rough finish and can't seem to get a nice wet coat. What in the hell am I doing wrong? Never had trouble shooting the clear pre cat lacquer.

Forum Responses
(Finishing Forum)
From contributor D:
What are the pressure settings on your fluid and air? Did you check your materials viscosity before spraying?

Fish tails? Are you referring to the gun spray pattern, or streaks in the finish? Tails created by the gun's tip (provided it is in good clean working order) can be eliminated by increasing the atomizing air. If the tip is dirty, or fouled, you will be adding too much air to compensate, creating a nightmare with your finish quality. Also, why the .513? Do you have a .411 tip?

From contributor E:
Your product may be too thick and you will have to check viscosity. Really thick stuff will have the tails and they are hard to break up. Set pressure on fluid to about 40 and then start increasing air just until the tails begin to break up. Shoot onto some cardboard. 513 is a big wide tip, I agree. If the finish is not laying out flat, it sounds like it needs to be thinned.

From the original questioner:
Thanks. Pressure settings are 23 air, 30 fluid. Mohawk gave me some reducer so it sounds as if everyone is on the same page. I'll try it and see if there is a difference.

From contributor E:
Do you have a gravity viscosity tester? Like a zahn or a Ford cup? Maybe they have one or you could order one online. If you are new to the lacquer it really helps to adjust the amount of thinner.

From contributor O:
I run mine at 40-45 fluid pressure and then if you have one, try a 411 tip. The 513 tip is more than likely a bit open for your clear coat.