Thinning and Gun Setting for Spraying Primer with Air-Assisted Airless Sprayguns

A newcomer gets advice on thinning and settings for an air-assisted airless spraygun. November 14, 2014

Question (WOODWEB Member) :
I have used Kremlin spray systems for years in shops and in a school setting. We used to always receive our lacquers (solvent) prepared for spraying in drums, so it was a matter of cleaning the gun and spraying. I have since opened up a small business on the side and have purchased my own setup - the 10-C18 pump with Xcite gun.

Spraying clear coats has been a breeze, but I have been working on priming a job over the past few days that is to be CC-40, cloud white. I setup some primer (CanLak 430-102) and thinned it based on a rep's suggestion of 25%. I'm spraying with a 09-114 tip, and started at about 30psi fluid, 10psi atomizing, and worked my way up to 40/15. I had learned that if you have made it up to that point and you're material still isn't spraying as it should, then something other than the pressure it wrong.

I'm getting an immense build-up of material on the tip of the gun. Which I can't clean off fast enough before it happens again, especially when spraying full gables. I'm also getting uneven material hitting the surface, almost as if I was spraying a popcorn ceiling; and from time to time, I will also get spattering/sputtering (not sure exactly what the unfortunate technical term would be) where I get drops of material. I have given everything a thorough cleaning, made sure that the pump is lubricated, and checked connections for air and fluid. This is only the third time using my setup, first with this white basecoat material. Any thoughts or input will be much appreciated!

Forum Responses
(Finishing Forum)
From contributor U:
It seems like you know your way around the finishing process and have checked everything out right. My guess is that it's still too thick and needs to be thinned more. Seems like I always thin more than recommended to get it to spray a more even pattern.

From Contributor E:
You’re air pressure is too low. Bring it up to 30 and drop your fluid to 30. That should help to break up the liquid. You need to get a viscosity cup to know how much too thin product if you want to do that. I am spraying some primer that is as thick as cake batter and the tip will gum up. Keep a wet rag handy to wipe after each unit you are spraying. Also check your small white seal inside the kremlin tip.

From contributor K:

We have better results spraying primer with a #12 tip on the Kremlin. Also, when I have problems with excessive buildup on the tip and sputter it usually indicated that the o-ring in the tip is worn and needs replaced. There is an o-ring on the fluid nozzle where the spray cap meets it. If air gets threw there it forces material out threw the atomization holes resulting in the symptoms you described.

From contributor R:
If it is cold in your shop you will need more thinner than when it is hot. Get a Zahn Cup to check your viscosity for consistency. We spray our primer with a 14 tip and it flows out like glass. With an 09 tip I think you should probably be around 20-22 seconds in a Zahn #2 Cup. If anything I wouldn't increase the air after the tails are gone you're just creating overspray, you can kick up the atomizing pressure though, maybe up to 45 or 50 and see if that helps. Personally I would go with a bigger tip.

From contributor H:
If you are getting material around the holes surrounding the tip, you need a new white o-ring inside the tip. If you have drips coming out of the tip you need to replace the seat. Going above 40 psi is no big deal and will not hurt the pump. Heavier bodied materials sometimes need that. When I spray ML Campbell Clawlock or Magna Claw primer maybe a little higher. I might look to get a 12 tip. The most I thin the Magna Claw is 10 percent. One other suggestion - don't store your pails on the concrete floor - elevate them.

From the original questioner:
Thanks for the replies all. I am going to try thinning a small batch of material a bit further as well as experimenting with the pressures. I should mention that the gun/pump is only two months old, bought brand new.

From contributor W:
With a 10:1 pump and a thick primer pump up the pump pressure without looking at the gauge. Adjust with the air off and pump pressure till you get the amount of paint as well as the quality in the center of the fan forget about the tail. Once you like the middle then turn on the gun air and adjust till the tail melt in. People get hung up on dials and think you adjust with those - not! When I sell a system and work with the painter I cover the gauges and teach the guy or gal to adjust to need and yes most lacquer salesmen won't tell the proper amount to thin.

From the original questioner:
So I played around a bit with some of the suggestions above. I found that thinning the primer by 40%, raising the fluid pressure to 50psi, and keeping the atomizing air at 10psi (when triggered) gave the best results. It's a bit of a learning curve setting this up and using it, but even just the primer went on nicer than top coats I have been able to do in the past. Amazing system! Thanks so much for the help! I'm sure it won't be the last time asking, but I feel like this was a pretty big step in the aforementioned curve.