Bubbles in HVLP waterborne finish

[Alan Lightstone]

Don't know what's causing this, but I'd love some advice how to eliminate this problem. I'm getting lots of small bubbles in the finishes I'm spraying with my HVLP gun. I'm a total HVLP newbie, so I'm not sure where I'm screwing this up. I'm using a Fuji XPC gun, and a Fuji Gold 4 HVLP turbine. Using a #3 needle/aircap (1mm, .039").

The bubbles remain after the finish dries, and are permanent.

Here's a picture of how they look:

IMG_1372-for-web.jpg

Any clue as to what is causing this, and any suggestions for eliminating the problem?

[Scott Holmes]

Are you sure it's bubbles and not dust? Difficult to tell in the picture.

[Alan Lightstone]

Pretty sure it's bubbles. Sorry, cell phone picture.

[Scott Holmes]

Maybe air that escaped from the wood.. Light sanding and another coat should fix it.

[Sam Hamory]

Alan,

Is it possible that the finish was shaken? If you shake a waterbourne finish or latex paint the bubbles stay in it all the way to the project.

[Howard Acheson]

What is the finish you are using?

[Scott Holmes]

Sam, he's spraying. I think the HVLP eliminated any bubbles that may have been in the finish due to mixing...

[Alan Lightstone]

It's Target Coatings EM2000, though I had a similar incident with General Finishes High Performance.

New Gun/Turbine, newbie to HVLP, so I'm thinking it's a setup issue. Just don't know what.

[Howard Acheson]

Let me suggest you purchase Charron's Spray Finishing. Amazon will have it. It will tell you about your equipment, how to set it up and adjust it, how to "read" the finish and how to best apply a finish.

Also, practice on scrap or cardboard boxes until you get to the point where you can get a good finish. Don't let a real project be your learning curve. Spray painting takes some learning and practice. You don't just point the gun and pull the trigger. In our shop apprentice finishers spent a week or two before they were allowed to spray anything important.

One final comment. To me, my first thought was dust particles. Are you spraying in your shop? Do you have a dedicated space or room you can use?

[Alan Lightstone]

Howard:

I'll check out the book. Thanks.

I am spraying in my shop. I keep my air cleaner on, and the Dylos has good readings before I spray.

I use a homemade spray booth. Fan with filter on the exhaust side, plastic sheeting comprising the walls and ceiling.
The back (air intake side) is open which could provide dust. I might partially enclose that in the future.

It doesn't look like dust to me. Certainly not like dust nibs I've encountered in slow drying finishes. It really looks like bubbles that have dried in place.

Alan

[Conrad Fiore]

Alan,
Do have the next largest N/N set for the gun? If so, try that, decrease your air and set your fluid control to where you get a full wet but not dripping coat at 6-8 inched from your work surface. I spray the EM2000 with both a turbine and HVLP conversion gun and it sprays and lays out nice with both. I run a 1.5mm in my 4 stage turbine and a 1.4mm in my HVLP conversion gun.

[robert raess]

Water-borne urethanes were first widely used and accepted by the wood floor industry.The first few generations were all prone to bubbling,which is aggravated by the quick dry time of the surface, which freezes the bubbles in the finish before they have time to pop.I have used[$100 gal. ]left over woodfloor water borne urethane to spray, and it was flawless.The thing imho,it seems like the flooring industry has got this anti-foaming thing down.I'm not sure if the rest of the industry can say the same.Some companies sell anti-foaming agents,i think similar to a surfactant.I have heard of guys in fine woodworking or fine home building write an article about 10-15 yrs. ago, and they recommended adding whole cream yes whole cream[i've never done that] to lessen the surface tension.I believe these anti-foaming agents use either propylene or ethylene gycol...the important thing is, i think your spraying skills are prob. ok, but the waterborne products are not all equal and they are not all friendly to use ...Rob

[Alan Lightstone]

Conrad:

I've tried a 1.4mm tip (the bubbles were with that) and a 1.0mm tip. I didn't think to try a larger one. I do have a 1.8mm tip. That's the next size up for the Fuji. I assumed that would be way too large for the viscosity of the finish. Fuji recommends using the 1mm tip for waterborne lacquers.

Robert:
I can really buy that explanation of the bubble freezing in place before it can pop. That's what it really looks like. Are there anti-foaming agents available that are compatible with present waterborne lacquers?

[Sam Hamory]

Hi Scott,

HVLP does nothing to remove bubbles if someone has shaken the gun with finish in it.

[Craig Coney]

Alan, did you thoughly clean your spray gun prior to using the WB finish? From what I see in the photo, it could be contamination (Oil) or dust. My HVLP gravity gun cup had a light coating of oil & I cleaned the gun completely prior to using it.

You may also want to attempt a thicker coat on a test piece and see if this helps correct the condition. GF purchased Compliant Spray Systems, CSS made modifier & conditioner additives for the WB enduro finishes to help with the drying time in different environments.

The #3 or #4 cap should be fine for what you are spraying.