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Spraying Oil based paint : Orange peel, globs, nothings working

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Forum topic by ChrisCarr posted 12-30-2012 08:24 PM 5870 views 0 times favorited 17 replies Add to Favorites Watch
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ChrisCarr

196 posts in 1553 days


12-30-2012 08:24 PM

I recently finished building a shelf out of mdf with a poplar faceframe. Construction of it turned out perfect (thats what i’m good at ) everything was great until i tried to use an hvlp gun for the first time. I am using the cheap $10 gun without a regulator from harborfreight. Every coat i put on turns out having either orange peel or spit blobs on top of it. I am using gloss oil based paint Tried several things with zero success ..

- Tried thinning the paint from 5% to 50% ... nothing gets rid of the orange peel or spit blobs
- Played with air flow settings, psi, material volume setting everything…
- Tried everything from 10 psi to 90 psi.
- Tried holding the gun closer, further and moving quicker and slower

I am starting to think its the gun, would have brushed it but wanted a glass smooth look.
So far i have spent 2 days sanding, doing test pieces, and recoating .
Any suggestions would be helpful

Also: compressor puts out 5.6 cfm at 40 psi. Didn’t strain paint, its new, and didn’t think i needed a water filter to spray on the compressor either.


17 replies so far

View bondogaposis's profile

bondogaposis

2528 posts in 1005 days


#1 posted 12-30-2012 09:04 PM

Did you strain the paint?

-- Bondo Gaposis

View Clint Searl's profile

Clint Searl

1455 posts in 1015 days


#2 posted 12-30-2012 10:10 PM

A ten dollar gun will give a ten cent finish. Use a brush.

-- Clint Searl....Ya can no more do what ya don't know how than ya can git back from where ya ain't been

View a1Jim's profile

a1Jim

112089 posts in 2231 days


#3 posted 12-30-2012 10:21 PM

I use those guns ,the ones I have works fine. I have heard others that have bought HF guns and say there hot and clod on their quality, but I’m on my forth one(given the others to friends) and they have all worked great.
It could be a faulty gun,to thick of paint or a dirty gun that has not been cleaned properly. Lastly it could be inexperience spraying.

edit
It could also be the wrong size needle or tip.

-- http://artisticwoodstudio.com Custom furniture

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404 - Not Found

2544 posts in 1623 days


#4 posted 12-31-2012 12:15 AM

A foam roller will give you a glass smooth result with oil based paint.
I can’t comment on your HVLP conversion gun as mine is used on a turbine, but orange peel is typically the result of too much paint or the paint not being thinned sufficiently. Spitting is due to the paint not being atomised properly because it’s either too thick or not enough air.
Did you get a viscosity (second) cup with the gun? It’s the only way of checking your paint is properly thinned.

View CessnaPilotBarry's profile

CessnaPilotBarry

890 posts in 764 days


#5 posted 12-31-2012 12:42 AM

I have a buddy who gets plenty good results spraying thinned Rustoleum with HF guns on metal items… One of the ways cheap tools get to be cheap is less rejected parts. Since you’ve NEVER had success with this gun, if all else fails, can you try a second $10 gun?

I would use a water filter in the air line, unless the compressor never cycles on and off while you spray. Cleanliness is godliness with spray guns.

I’d follow the info from the others above, starting with a super clean gun and strained paint thinned to a proper viscosity. Orange peel can also result from thick paint applied with a lot of warm air drying quickly. My turbine rig can get the air warm enough to make finish dry too fast, but I usually only have the problem with lacquers and water base, not enamels or varnishes.

The only other question I can think of is the paint fresh, and the solvent correct for the paint, fresh, and a well-known brand? What are you using for thinner?

Also, are you spraying into your own overspray? This applies wet finish on top of dryer overspray, not overspray on semi-dry finish. If you were spraying a flat board, the correct way is to spray the front edge, then overlap the passes as you move away from you. Dusty overspray is often confused for orange peel by newbies.

Photos of defects with proper names: http://www.mig-welding.co.uk/paint-faults.htm

-- It's all good, if it's wood...

View ChrisCarr's profile

ChrisCarr

196 posts in 1553 days


#6 posted 12-31-2012 01:28 AM

I took a look at that link CessnaPilotBarry, The pictures of overspray and dust contamination look like what i have as well as the one with water and oil contamination. I can try one of those cheap filters that go on the end of my air hose harborfreight has if i could make a difference?

Also the “blobs” or spitting i get on my work get worse when i’m finished and go back and check.

Also i never go a cup with my gun to test thinning but i thought 10 -20% thinned seemed about right for oil based.

View jim454's profile

jim454

35 posts in 1067 days


#7 posted 12-31-2012 02:37 AM

The spray is very blotchy/spatters. The paint requires thinning further (33.3 ounces to 4.3 ounces of the appropricate thinner).

Orange Peel - Improper gun adjustment and techniques. Too little air pressure, wide fan patterns or spraying at excessive gun distances causes droplets to become too dry during their travel time to the work surface and they remain as formed by gun nozzle. Extreme shop temperature. When air temperature is too high, droplets lose more solvent and dry out before they can flow and level properly. Improper dry. Gun fanning before paint droplets have a chance to flow together will cause orange peel. Improper flash or recoat time between coats. If first coats of enamel are allowed to become too dry, solvent in the paint droplets of following coats will be absorbed into the first coat before proper flow is achieved. Wrong thinner or reducer. Under-diluted paint or paint thinned with fast evaporating thinners or reducers causes the atomized droplets to become too dry before reaching the surface. Too high viscosity. Low shop temperature. Too little thinner or reducer. Materials not uniformly mixed. Many finishes are formulated with components that aid coalescence. If these are not properly mixed, orange peel will result. Substrate not sanded thoroughly

View woodman71's profile

woodman71

162 posts in 1978 days


#8 posted 12-31-2012 04:05 AM

You must have a regulator on your gun why let say you need 40 psi to spray that mean with a regulator you can see what you have at the gun. But if you what 40 psi to spray with a regulator you test spray when your spraying your psi will drop with a regulator you can see what psi is when the gun is open should be 40psi open that’s the point of a regulator. I have a good feeling that what it is regulating at you compressor is wrong for spraying you lose to much pressure in the line and like I said when you start spraying the line pressure drop to fast and you have bad spraying gun.

View NiteWalker's profile

NiteWalker

2710 posts in 1231 days


#9 posted 12-31-2012 04:41 AM

I sprayed rustoleum thinned with mineral spirits before. It’s very picky and will run at a moment’s notice. Good paint though; very durable.

-- He who dies with the most tools... dies with the emptiest wallet.

View PaulLL's profile

PaulLL

148 posts in 630 days


#10 posted 12-31-2012 04:49 AM

Your issues could be caused because your air compressor isn’t putting out enough air. 5.6 is pretty low volume, usually an HVLP gun requires around 12 at about 40 psi, it’d probably be cheaper to get a regular spray gun instead of a new compressor.

View pintodeluxe's profile

pintodeluxe

3360 posts in 1467 days


#11 posted 12-31-2012 06:27 AM

Is yours a gravity-feed HVLP gun? For years I struggled with a siphon feed “HVLP” gun that would barely spray. It did well on horizontal surfaces, but it would spit and sputter on vertical surfaces. I later switched to gravity feed HVLP guns, and for me it made all the difference. Since gravity does the work, you can dial your pressure back. Paints usually require a 2.0 mm tip and nozzle set. My two guns (Wood River and Porter Cable) came with a 1.5 mm nozzle set. The 2.0 mm sets are readily available for those guns.
The Wood River gun is only $40 and available at Woodcraft. Extra nozzle sets are about $10.
Good luck. Don’t give up, spraying can be one of the most rewarding parts of woodworking.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View DannyB's profile

DannyB

46 posts in 2076 days


#12 posted 12-31-2012 05:24 PM

Wheee.
Use a brush. Not because of any other reason than “it’s crazy to try to spray oil based anything”. The last thing you want around you is atomized lighter than air oil droplets that hang around and attach themselves to everything. If you want to spray a fence or the exterior of a house with oil based stuff, go for it, just don’t try to do it to anything fine.

If you really want a glass smooth finish, don’t use paint, use a woodworking finish (You can get finish tinted the same as you can paint).

If you really want to ignore this advice, and spray it anyway, you have three issues:
First, you need a regulator on the gun. Period. You need to get the right pressure at the gun, and the only sane way to do this is to put a regulator near it, pull the trigger, and make sure the trigger-pulled PSI matches what the gun requires. You also need an in-line filter. Finishes are not tolerant of contamination.

Second, those guns don’t come with anywhere near a large enough needle to spray paint, unless you were to thin it to probably 80-90%. It’s just too viscous. You really need a larger needle set.

Third, the aircap on that gun is not particularly good at atomizing, so you are going to get some amount of orange peel anyway.

View Earlextech's profile

Earlextech

979 posts in 1345 days


#13 posted 12-31-2012 05:37 PM

jim454’s long explanation comes down to this – orange peel is the result of the finish drying too fast.
I don’t see any mention of Penetrol, which will extend the dry time and allow the finish to flow out properly.
Needle size makes a difference, distance from project makes a difference and paint flow rate makes a difference. And I can’t even be civil about a conversion gun, I just don’t like them.

-- Sam Hamory - The project is never finished until its "finished"!

View ChrisCarr's profile

ChrisCarr

196 posts in 1553 days


#14 posted 12-31-2012 11:27 PM

I put a regulator on it and the filter today. Running the gun regulator at 40 Results are MUCH better , very little orange peel and almost glass smooth, however theres still 2 or 3 little blobs and i managed to get some drips (the drips were mainly because i was rushing outside because the sun was setting).

But i am having problems with my passes leaving slight streaks (zebra – style when you shine a light up close). What is the cause of that?

Is there anything like polishing compound i can use to buff/poslish the finish “perfect” that wont dull the gloss finish too bad?

View DannyB's profile

DannyB

46 posts in 2076 days


#15 posted 01-01-2013 02:39 AM

Can you take a picture?
It’s hard to tell if you are saying the finish is actually uneven, or the light shines on it uneven, or something else.

If the finish itself is uneven, it’s probably from holding the gun at an angle, instead of straight on all the time.

You can usually buff it, but you will have to wait for it to completely cure, and be very gentle.

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