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:

207785

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.

[Alan Lightstone]

I did not clean the gun entirely prior to using it. I had sprayed some test pieces before this one. I guess contamination in the gun is possible. I have sprayed water through the gun several times cleaning it out at the end of the day, but I have not used any other cleaning solvents in it.

No gun shaking, unless there are gremlins in my shop after I turn the lights off.

I actually did try a couple of test pieces with heavier coats with the #4 cap on it on GF High Performance. I'll have to look again, but I think they have a few bubbles too.

[Jerome Hanby]

I was watching a Wood Whisperer video the other day about spraying finishes and one of the questions he answered concerned water based (same as bourne?) finishes sprayed with HVLP. His comment iwas that he always got bubbles and had quit trying to spray it. He didn't offer any reasons or analysis, just his decision based on trying it. I know he has used the Apollo 4 stage unit, and the Earlex 2 and 3 stage units, but I don't if he was speaking about a particular unit when he made his statement.

[John Coloccia]

I've never used EM2000 but as a start I would suggest possibly trying to thin with just a drop of water and reducing the air pressure. Maybe 1oz in a quart for thinning...something like that. Also, contact Target. Their customer service is top notch, and they're very knowledgable. Also you can try their message board. Don't be surprised if you get a response directly from Jeff, the owner.

[Craig Coney]

I would try to clean out your gun thououghly with paint thinner then lacquer thinner, disassemble as far as you can. I would suspect there is some contamination causing the problem.

[ray hampton]

I would try to clean out your gun thououghly with paint thinner then lacquer thinner, disassemble as far as you can. I would suspect there is some contamination causing the problem.

is this paint affect by fish-eye ?

[Alan Lightstone]

I'll take it apart and clean it. Paint thinner and Lacquer thinner are the right solvents to use, even though the gun has only ever seen waterborne finishes?

[John Coloccia]

I'll take it apart and clean it. Paint thinner and Lacquer thinner are the right solvents to use, even though the gun has only ever seen waterborne finishes?

Waterborne finishes are not water soluble. They are bits of finish combined with bits of solvents, all suspended in water. When the water evaporates, the solvent flows the finish...then the solvent evaporates. What's left is usually impervious to water as the water was never the solvent. All the water does is act as a carrier so that you can cut out most of the solvent.

[Jamie Buxton]

Hi Scott,

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

I'm with Scott on this one. The sprayer breaks the finish up into extremely tiny droplets -- much smaller than anything your eye can see. Air bubbles wouldn't survive that. As it happens, I'm pretty careful to vigorously shake my finish cans before I spray them. I want consistent sheen, and shaking the can helps get all the flattening agent in suspension. I don't see any bubbles in the cured finish.

Now, a brushed finish is a different case. I think the stricture against shaking the can is left from the days that brush was the dominant form of application.

[Bob Wingard]

Hi Scott,

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

Are you saying that atomization does NOT remove bubbles ???

[Rob Cunningham]

I would run some denatured alcohol through the gun, you do not want to use mineral spirits as this will cause contamination problems. It's possible that you are spraying too heavy of a coat or too much air pressure Try backing off the fluid adjustment and the psi a little.

[Mike Goetzke]

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:

207785

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

Alan - I have the gravity fed XPC gun and Q4. I struggled quite a bit with bubbles but attribute that to finish quality (returned bad finish for new) and user inexperience. I am using EM6000 for my kitchen cabinets and have come up with the following. Turn the turbine out air valve to about 75% to 80%, use the blue air cap (it's the one you mentioned), turn the fan spray control to about 75% forward (to get about a 5" to 6" fan when you are about 8" from the surface), and my needle is backed out maybe 1-1/4 turns (but, I set it up to get 2-3mils thick coat). I also use the Fuji cup and try to get 18 sec. till you just see it drip. I move the gun at maybe 18"/sec and overlap passes by 50%. I place a light so I can see my spraying on all passes and place the turbine on the floor about 10' to 15' from where I'm spraying. I use to get quite a few bubbles (I experimented quite a bit and somehow the bubbles seemed to be generated at the surface) and don't see many now. The ones that do occur level out and don't leave any marks. With these WB finishes I try not to look at the piece I just coated as I place it on the drying rack:D.

Mike

[Jason Roehl]

I've done much more airless spraying than HVLP, but I've done plenty of that, too. What I see in the pic looks like contamination of some sort--either bits of dried finish coming through the gun or dust embedded in the finish. I've never seen bubbles in waterborne finish survive spraying. Heck, I even shake WB finishes when I brush or pad them and don't have bubble problems. Bona WB floor finishes even instruct the user to shake prior to (non-spray) application. I have found that over-working a WB finish with a brush will cause bubbles, though (between floors, log home interiors and trim packages, I've probably applied several hundred gallons of various types of WB finish).

You may need to strain your finish or clean your gun better (lacquer thinner is an excellent solvent for this--it will loosen/dissolve many finishes). Also, I prefer dead air when I spray until the finish sets up. Otherwise there is just more dust being stirred up and potentially landing on the work surface.

[John TenEyck]

I skimmed some of the responses so I apologize if I'm plowing the same ground twice. Anyway, I've sprayed a fair amount of GF Hi Perf. Poly and never had bubbles. The photo you posted looks like a very heavy coat to me. I try to put on the thinnest coat that still wets out, especially when spraying vertical surfaces. But more importantly is that the finish needs to be of the correct viscosity for your gun/orifice. I followed Jeff Jewitt's advise for my gravity feed HVLP conversion gun, which is about 45 seconds through a Ford #4 cup for my 1.4 mm orifice. That required thinning the GF product 10%. I use water and it works just fine, sprays beautifully, and no bubbles. Adding wetting agents, surfactants, etc. would be my last move and, so far, I haven't had to pursue them.

[Alan Lightstone]

Lots to think about and try here. It certainly seemed like a thick coat. I think the 1.4mm orifice is large for the GF Hi Perf. Obviously you're doing fine with it, John. I did think it about 10 percent. I don't recall what my viscosity was with the included cup. I need to get a wet film gauge. Don't have one.

I'll have to try your settings, Mike.

[michael gates]

Hard to tell from the pic but it looks like pinholes. You need to thin your lacquer more. Contact your supplier for a proper thinner. Butyl Cellosolve will work, water will not.

[David Weaver]

I had this trouble with some waterborne stew mac lacquer. I went up in pressure and down in coat thickness. I had bubbles on thick coats, and no bubbles in thin coats. I kind of doubt the pressure did anything to fix the issue, but bet the thickness was all or 99% of the fix.

You're going to have the urge to make the finish look wet with waterborne, but I think if you do get a wet look, if that's at all like stew mac water lacquer, you're going to get bubbles if you get it that far.

Try thin coats, many of them. The several times I've done thin coats, I've done about 15 coats of lacquer 15 minutes apart, and the finish turned out great. Every time I tried to do 5 thick coats, I got bubbles. If I added retarder, some of the bubbles popped, but not all of them, and half as many bubbles still sucks when zero bubbles is what you want.

[Alan Lightstone]

Interesting