# HVLP Spraying



## Dan Gal (Sep 17, 2013)

I used a gravity feed HF purple HVLP gun for spraying polyurethane. First coat went on OK but I clouded up my entire garage. I had the compressor set for 45-60 PSI. Any suggestions to avoid the cloud or is that just the nature of the beast?


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## Steve Neul (Sep 2, 2011)

Well, the high pressure made it worse but you can't prevent polyurethane from drifting. You might consider using lacquer or shellac instead. They dry so fast what drifts settles like dust and won't adhere. Another option would be to construct a spray booth but it needs a exhaust fan with an explosion proof motor and they are expensive. You could also create a spray booth where you were blowing clean air into the booth with a box fan however if it wasn't filtered very well you would be blowing dust into the finish. Another option would be to spray poly outdoors.


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## woodnthings (Jan 24, 2009)

*here's what I do*

I set the regulator at the compressor at 55 PSI. I have a 3/8" X 50 ft hose, actual inlet size about 1/4" because of quick change fittings. I have a second regulator at the gun to reduce pressure to about 40 PSI. The air volume knob at the guns inlet is the way to control your air out of the gun. If this is wide open you will get a lot of air and not enough paint, so do some test pattern. 

The viscosity is important to reduce overspray/misting and room filling clouds.... A slightly thinner mix will spray and flow out better, than a thicker mix which will orange peel and dry out rough.

You should practice on a horizontal surface to get the gun working right and the correct mix. Vertical surfaces are hard enough to spray without runs, let alone a poorly set up gun and a watery mix... BTDT :yes:


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## Dan Gal (Sep 17, 2013)

Thanks for the tips!


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## JCCLARK (Jan 30, 2007)

You need a regulator at the gun, the fittings and hose length
drop the final pressure and CFM a lot.
With std hoses and fitting you won't get the CFM needed for
a HVLP gun unless you run much higher pressure (PSI) to
the gun and then regulate the pressure down at the gun
with a gage to read it.
The pressure needed at the gun varies a lot depending on the brand.
Set the pressure to the gun you are using, check the specs.
My guns vary between 23 PSI and all the way to 45 PSI.
Those are inlet pressures needed to obtain the 10 PSI at the tip that
most HVLP guns deliver.
Most painters up it about 5 PSI to spray better.
But every gun is different so you need to experiment a little.


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## Dan Gal (Sep 17, 2013)

Thanks again for the tips.I let up the pressure a bit and thinned out the poly a bit. Not saying "not a cloud in the garage" but it was significantly better and cleared out in 1/10th of the time.


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## RandyReed (Jul 30, 2014)

There are alot of posts about spraying and compressors here lately. 

For the people with over spray problems and small compressors, they should look into an LVLP gun. LVLP has a softer spray with the lowest overspray levels on the market, and assuming LVLP guns are maintained well, they are a joy to work with.


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## Steve Neul (Sep 2, 2011)

I never could see how they could call a HVLP sprayer high volume. Any I've ever used put out at best 75% of what you could do with a siphon sprayer.


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## sancho57 (Oct 23, 2011)

What JCClark said.


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## NickB (Sep 24, 2013)

Steve Neul said:


> I never could see how they could call a HVLP sprayer high volume. Any I've ever used put out at best 75% of what you could do with a siphon sprayer.


I always thought it was the air volume vs air pressure. HVLP relies on blowing a high volume of air into the material in order to get it to atomize. I don't think they mean material volume.

I think that anybody who had an opportunity to use a good conventional gun, then later switch to HVLP would agree that you could lay more material, faster and with better atomization with the old guns. I guess the trade off was efficiency, though. It blows my mind sometimes how little material I use when spraying HVLP...


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## Al B Thayer (Dec 10, 2011)

NickDIY said:


> I always thought it was the air volume vs air pressure. HVLP relies on blowing a high volume of air into the material in order to get it to atomize. I don't think they mean material volume.
> 
> 
> 
> I think that anybody who had an opportunity to use a good conventional gun, then later switch to HVLP would agree that you could lay more material, faster and with better atomization with the old guns. I guess the trade off was efficiency, though. It blows my mind sometimes how little material I use when spraying HVLP...



Your correct. High volume of air at a low pressure results in less wasted material. More material on the wood than in the air and on the floor. There's no question it's more efficient. But I believe you need to spend a little money to get one that finishes well. 

Al


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## RandyReed (Jul 30, 2014)

NickDIY said:


> I always thought it was the air volume vs air pressure. HVLP relies on blowing a high volume of air into the material in order to get it to atomize. I don't think they mean material volume.
> 
> I think that anybody who had an opportunity to use a good conventional gun, then later switch to HVLP would agree that you could lay more material, faster and with better atomization with the old guns. I guess the trade off was efficiency, though. It blows my mind sometimes how little material I use when spraying HVLP...


Totally agree.
Conventional air spray air cap pressure is nearly the same as the input pressure entering the spray gun. HVLP technology reduces the incoming pressure to a compliant 10 psi or less at the air cap.

If you supplied an HVLP with only 10 psi inlet air pressure to a spray gun, the volume of air would be too limited for most industrial applications. 

ou also should spray a little different between the two different guns. Use 8-10” for conventional air spray and 6-8” for HVLP.


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## RandyReed (Jul 30, 2014)

Al B Thayer said:


> Your correct. High volume of air at a low pressure results in less wasted material. More material on the wood than in the air and on the floor. There's no question it's more efficient. But I believe you need to spend a little money to get one that finishes well.
> 
> Al


True. The higher end guns atomize material better.

HVLP guns, like all spray guns need to be matched to the application. Spray guns and air caps are available to handle the needs of the touch-up artist to the requirements of heavy industrial applications.


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## Al B Thayer (Dec 10, 2011)

Wow. All these posts and not a single ad for HF. 

Al


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## woodnthings (Jan 24, 2009)

*well, not an outright ad ....*



Al B Thayer said:


> Wow. All these posts and not a single ad for HF.
> 
> Al


If you look closely you will see my purple HF gun in it's HF cradle, with the disposable HF filler cup, clamped to the plywood work bench on the upper left of this photo... a stealth ad:

 

:smile:


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## Al B Thayer (Dec 10, 2011)

woodnthings said:


> If you look closely you will see my purple HF gun in it's HF cradle, with the disposable HF filler cup, clamped to the plywood work bench on the upper left of this photo... a stealth ad:
> 
> 
> 
> :smile:



Ya just hada go n ruin for me. Dent ch?


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## NickB (Sep 24, 2013)

RandyReed said:


> You also should spray a little different between the two different guns. Use 8-10” for conventional air spray and 6-8” for HVLP.


Are you talking distance from the surface? or width of fan?


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## RandyReed (Jul 30, 2014)

NickDIY said:


> Are you talking distance from the surface? or width of fan?


Distance from gun to piece being sprayed.


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## Quickstep (Apr 10, 2012)

RandyReed said:


> There are alot of posts about spraying and compressors here lately.
> 
> For the people with over spray problems and small compressors, they should look into an LVLP gun. LVLP has a softer spray with the lowest overspray levels on the market, and assuming LVLP guns are maintained well, they are a joy to work with.


I've been reading a lot about LVLP guns lately and the softer spray. One of the guys on my luthier forum says he sprays the first 10 coats using an HVLP gun, then shoots the final coat (or two) with an LVLP gun. 

This makes we want an LVLP gun, but having just gotten an HVLP gun, I'm not eager to pour a lot of $$ into another gun, but I was wondering about this LVLP gun by Sprayit. It seems to have gotten good reviews. Thoughts?

http://www.homedepot.com/p/SPRAYIT-LVLP-Mini-Gravity-Feed-Spray-Gun-SPRAYIT-SP-33500/204343810


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## JCCLARK (Jan 30, 2007)

I don't think you'll notice that much difference
(if they're both equal in quality level)
An expensive HVLP will way outperform a cheap LVLP,
and vise-versa.
I use both and really haven't noticed much difference at all.


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## RandyReed (Jul 30, 2014)

Quickstep said:


> I've been reading a lot about LVLP guns lately and the softer spray. One of the guys on my luthier forum says he sprays the first 10 coats using an HVLP gun, then shoots the final coat (or two) with an LVLP gun.
> 
> This makes we want an LVLP gun, but having just gotten an HVLP gun, I'm not eager to pour a lot of $$ into another gun, but I was wondering about this LVLP gun by Sprayit. It seems to have gotten good reviews. Thoughts?
> 
> http://www.homedepot.com/p/SPRAYIT-LVLP-Mini-Gravity-Feed-Spray-Gun-SPRAYIT-SP-33500/204343810


The main difference is the over spray. You will not have nearly as much with the LVLP, and is good to use where there is not alot of ventilation. LVLP is also good for people who are just learning to spray as the gun runs slower so the person can concentrate on their form and technique, and its easier to make adjustments. LVLP guns can also cause dry spots. You can spray with a 110v pancake compressor. LVLP does not require as much psi at the tip to atomize.

As far as hvlp, that technology is great for industrial tasks, cause just a 5% paint saving could mean thousands for the company in the long run. HVLP guns are for the more experienced painters. Sprays very fast. Some HVLP guns you need a good size compressor to use, and you get complete coverage.

As for myself, I use whatever gun meets the task. A conventional gun is always my go to in guns when Im looking to spray large pieces quickly. Seems whenever I use an HVLP, I always need to use 15% retarder to avoid overspray when spraying entertainment centers, cabinets, etc.


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## Quickstep (Apr 10, 2012)

My issue is not so much about overspray as it is about orange peel. Through practice and some thinning and retarder, I've got it to a very minimal level, but not completely gone. The guy I talked about on the luthier forum, says he gets zero orange peel on the final coats when using the LVLP gun.


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## woodnthings (Jan 24, 2009)

*I got no orange peel on the truck hood*

I used the cheapest gun you can get, the "purple gun" from Harbor Freight and get a great gloss finish holding the gun about 6" or so away and overlapping each pass by about 50%, for a full wet coat. If it's not wet I give it another pass immediately until I see a good reflection.

The paint I use is pretty thin and sprays well. It's a catalyst type urethane epoxy. 

You may want to take your gun completely apart, clean it an soak the nozzle in some strong thinner for several hours. Use a very fine wire to clear out the air passages. I did this just lately and discovered a hidden bit of buildup on the moving rod. It worked much better after.

Before you buy a different gun ... LVLP ...I would make certain that your gun is clean and try spraying a different product, paint or other clear finish. Make certain your pressure at the gun is 30 to 40 lbs and adjust it with a gun mounted regulator. 

Either your gun isn't working right...
you are holding it too far away ....
or your mixture needs to be a bit thinner.
Make some test panels, I use 8" square aluminum roof flashing. It's cheap for a bundle and comes either raw or painted in brown or black. Keep track of each variable as change them, one at a time.


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## nwoodward (Feb 2, 2014)

I hung plastic over a wall and taped about 10 feet of thAt brown 36" roll paper to the plastic. I've been practicing form and attempting to spray a cigar while side stepping and moving my arm. Mentally I hope it helps build some muscle memory.

Sent from my iPhone using Wood Forum


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## Quickstep (Apr 10, 2012)

Either your gun isn't working right...
you are holding it too far away ....
or your mixture needs to be a bit thinner.


The guy from the luthier forum who recommended using an LVLP gun suggested that the orange peel I'm getting is a result of the velocity of the air hitting the surface and making dimples that don't flow out before the finish begins to dry. I've thinned the finish 33% and added 5% retarder and that seemed to improve things, but I didn't want to add _too_ much retarder.


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## RandyReed (Jul 30, 2014)

Quickstep said:


> Either your gun isn't working right...
> you are holding it too far away ....
> or your mixture needs to be a bit thinner.
> 
> ...


You dont need more retarder, especially when it gets colder.

If you are still getting orange peel, meaning the paint is coming out in too big of droplets, then you can turn down the fluid, unless you have the fluid too low and it is peppering the panel..Its very subjective.. Some people say more fluid equals more orange peel, while others say less fluid equals more orange peel. As long as the finish has time to level out and get tack free, it shouldnt have orange peel, and the butyl acetate I told you about will help it flow out.

Here is a good read about adjusting a spray gun by Brian Martin:
http://www.autobodystore.com/ms6.shtml


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## woodnthings (Jan 24, 2009)

*it was my quote....*



woodnthings said:


> Before you buy a different gun ... LVLP ...I would make certain that your gun is clean and try spraying a different product, paint or other clear finish. Make certain your pressure at the gun is 30 to 40 lbs and adjust it with a gun mounted regulator.
> 
> Either your gun isn't working right...
> you are holding it too far away ....
> ...


not quickstep's .... :no:


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## Quickstep (Apr 10, 2012)

RandyReed said:


> You dont need more retarder, especially when it gets colder.
> 
> If you are still getting orange peel, meaning the paint is coming out in too big of droplets, then you can turn down the fluid, unless you have the fluid too low and it is peppering the panel..Its very subjective.. Some people say more fluid equals more orange peel, while others say less fluid equals more orange peel. As long as the finish has time to level out and get tack free, it shouldnt have orange peel, and the butyl acetate I told you about will help it flow out.
> 
> ...



I've used both butyl acetate and Behlen's proprietary thinner. (The proprietary thinner is something like 1/3 butyl acetate) I have just a little bit of orange peel either way. Your explanation is helping make sense of it for me. I was trying to get it as wet as possible without runs, but I never thought about how that would affect droplet size. It was pretty darn warm when I last sprayed. It's getting cooler now. It will be interesting to see how things look on the next go.


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## RandyReed (Jul 30, 2014)

Quickstep said:


> I've used both butyl acetate and Behlen's proprietary thinner. (The proprietary thinner is something like 1/3 butyl acetate) I have just a little bit of orange peel either way. Your explanation is helping make sense of it for me. I was trying to get it as wet as possible without runs, but I never thought about how that would affect droplet size. It was pretty darn warm when I last sprayed. It's getting cooler now. It will be interesting to see how things look on the next go.


If i remember right, your using a smaller gun or kinda like a touch up gun??? If so, its hard to spray larger pieces with a smaller gun. Small pieces you still should not be seeing any orange peel.


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## Quickstep (Apr 10, 2012)

RandyReed said:


> If i remember right, your using a smaller gun or kinda like a touch up gun??? If so, its hard to spray larger pieces with a smaller gun. Small pieces you still should not be seeing any orange peel.



Yep, that's right. I'm using a smaller gun and spraying smaller pieces. The piece I'm practicing on is 4" wide. It looks nice and wet and it seems like it wants to flow out, but it just can't make it.


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