Troubleshooting Pinholes with an Air-Assisted Airless Spraygun

Fluid and air pressure adjustments can solve this problem. July 14, 2010

I just got a Kremlin 10-14 with the Xcite gun. I am spraying Richelieu water base lacquer and I have tried the pressures everywhere, but I can't get rid of the pinholes. I'm using an 06 - 114 tip. From what I have read here, I think I just need a different tip (ultra fine). Is that correct?

Forum Responses
(Finishing Forum)
From contributor J:
Not sure about the tip size, but in my setup, pinholes are a result of the fluid not flowing together well. My gun is a Graco 395 AAA with solvent based products, but all winter I faced pinhole issues due to temperatures. Most of my pinholes occurred on vertical surfaces with pigmented products!

From contributor D:
Are they pinholes or bubbles? 06-114 tip is a fine enough tip. You may like an 09-092 tip better. I find that the 04 tips clog a lot and that I have to keep the gun tip in a coffee can with 50/50 methanol and water. I get bubbles in the finish and it could be air escaping from the substrate or micro bubbles grouping together and coming to the surface. Check your viscosity and it should not exceed 40 seconds in a CA4 cup. Keep the fluid pressure at about 30-40 and then move your air starting at 0 increasing to no more than 25 to get rid of the tails. The fluid pressure gives you the amount of fluid coming out of the tip, so 30 gives you so many oz. per minute and 50 gives you that much more. So fluid pressure will not eliminate the tails. I find the higher the fluid pressure, the more micro bubbles. If your gun is brand new you should flush it with multipurpose solvent to get rid of oils inside the hoses before the water base. Make sure air supply has a filter for oil and gunk.

That said, you might be applying too much material because the gun is new to you, which will cause bubbles and pinholes. On large panels I will use a 12-154 tip, but the gun really has to move.

I spray about 5-10 gallons every week of Target waterborne.

From the original questioner:

They are micro bubbles that dry to pinholes. The more pressure I add, the more I get. The first couple pieces I sprayed came out good, then I started getting the micro bubbles. My fluid pressure is at 48 and my air is at 12-14 to get rid of the tails. I tried my pressure at 30 and it still has the bubbles. I also tried spraying thinner coats and holding the gun farther away and this didn't help either. I also removed the tip and re-primed the pump.

What is the difference between the 092 and 094 tips?

From contributor S:
I've sprayed thousands of gallons with airless. The tails are caused by too thick paint. Use the correct tip for the speed you need to go or for how difficult the job is to spray. Cubbies and in and out - small tip, panels - big tip. Thin until the tail is gone. The pressure should stay in one place all the time and use thinning and tip size to regulate paint. Too much pressure is going to cause heavy paint where you pull the trigger and cause runs, and also may cause the gun to spit.

From contributor D:
What kind of wood are you spraying? Do the bubbles occur on a second coat as well? You could add a bit of retarder and one I use is XIM from the paint stores. It is glycol which increases the open time, slows drying and allows the bubbles to pop. You may have to blow some clean air on the most problem surfaces to pop the bubbles. It could be temperature or humidity in the shop, so you may have to vary these things. Don't know the exact answer there, but my shop varies a lot in temp/humidity. Sounds like the fluid and air are okay; maybe 48 is a bit high. I find over 42 is pushing it. I personally would not thin the material too much with water because then you are reducing solids content. This may work for you, however, as I see contributor S thins his.

The 09-092 has an internal atomizer, so sprays a bit nicer than the 09-094 tip, but the 092 may clog more with waterbased. I prefer the 09-094 and the 09-114 tips

From the original questioner:
The pressures were at 12 and 42.

From contributor P:
Maybe the finish is foaming. Could be the pump is not properly primed. Spray the finish into the pail for 15 seconds with no tip. You should have a nice even stream with no sputtering. It could also be an air leak in the pump. Is it new? How often is the piston cycling?

From contributor U:
Holding the gun too close to the board will also give a bunch of pinholes. It needs to be at least 8" above, 10" is usually better. I learned this the hard way.

From the original questioner:
The only way I have found to get rid of these is to put a wet coat on, then the pinholes appear, and if I hit it again I can get rid of almost all of them, but this is really putting a lot on.

From the original questioner:
I just noticed that when the Kremlin rep set everything up for me, he gave me lubricant for my pump and I'm using waterbase. Is this what's giving me my problems?

From contributor D:
Do you have a film gauge? Should be max 4 mils wet. Too much liquid pressure - cut it back to 30-35. You may be sucking air in the pickup rod as well, so check all your connections. An 06 tip is fine, so you will put on less. Don't go back over the wet with another layer of wet; it'll be worse.

It's not an oil problem; it's an air/pressure problem from what I see.

From contributor E:
I have the Kremlin with the MVX gun, and I was getting excellent results spraying Fuhr 380 at 25 fluid pressure, and 30 air pressure. It looks to me like you are putting way too much finish on.

From the original questioner:
In an earlier post I made a mistake and called them micro bubbles, but they are definitely pinholes.

From contributor L:
May be solvent pop. Find an optimum temperature for material and spray area. Turn off/down fan after spraying. Let previous coat dry longer. Spray thinner coat.

From contributor T:
Is the substrate cold compared to the material? That can cause pinholes from thermal shock. Also, in addition to too thick wet film build, viscosity can cause the issue. Try this... Take a small amount of the waterbased material in a container, and place that container in a bucket of very hot water. Stir the material and reduce its viscosity with the heat from the hot water. See if that does the trick. Try to get the waterbased material to 90 or 95F. That should thin the viscosity and perhaps improve your result.

From the original questioner:
Nothing has worked so far. My rep was down for most of the day yesterday and can't find the problem. We tried another pail of lacquer and tried Chemcraft Aqualac as well. I guess I will return this system after the weekend and see if I can try another new one, because there must be something wrong with mine. He can use these products with the one at their shop with no problems.

From contributor M:
Am I the only one that got emailed this link from AWFI reviewing the Kremlin Xcite?

"The only materials that did not spray well through the gun were two-component urethanes and some water-based products. The gun appeared to cause micro-foam to form in the finish that remained in the coating after the finish was dry. With most of the materials in which the spray gun caused micro-bubbles, the problem could easily be rectified by re-formulating the coating material. Further testing will be conducted to resolve these minor issues. This article will be updated to include any new solutions that are discovered as product testing continues. The only other factor one needs to consider with the new gun design is that many parts cannot be interchanged with previous spray gun models."

From contributor V:
I have been doing a lot of work with water born coatings over the past month. There are several areas that I believe are very important to look at. First, this is a water based coating. I would always recommend a tip ending in "2". This style has a pre-orifice in the tip, which is used to overcome the thixotropic nature of water based coatings. What that means is the coating will reduce in viscosity when energy is added to the coating. This is the same thing that happens with catsup. It is very thick until it is shaken (or energy is applied to the catsup) at which time it falls in viscosity.

The second item is the film build. With water, you should try and maintain a wet film of no more than 3 mils. More will result in bubbles. 3 wet mils will result in about 1 mil dry film build.

You noted you were using a 06-114 tip. I would change to a 06-112 tip. The atomizing air pressure should be about 15-20 psi. The fluid pressure should be as high as you can go and still have good film build control. If you can go to 50 psi air pressure on the pump (500 psi fluid pressure) you should eliminate most of the bubbles.

A little slow solvent added to the coating should take care of what remains. The slow solvent will leave the wet film open and allow anything that remains to get out of the coating.

From the original questioner:
I solved my pin hole problem by running the air pressure at 30 and fluid at 50 with an 09 tip.