What Causes This? HVLP Paint Spraying

metahugh

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I am using a Husky HVLP gun which has a max operating presure of 40psi. This coat was sprayed @ 20psi. The paint is Rustoleum Semi Gloss Oil Based Black. I have thinned the paint 4:1 (2 oz of Naptha to 8 oz of paint).

I have also sprayed at 40psi but I think that puts down too much paint. I am thinking I might be using too much thinner. This is my first real paint job with an HVLP gun so I am still trying to learn the ropes. Thoughts?
 
Those are called "fish-eyes"

I sign of surface contamination

Your paint could be contaminated or more likely the surface.

One fix is a "fish-eye" eliminator that the real paint stores have (Sherwin Williams) to use when you are spraying and you see them while the paint is wet.

But this product introduces contamination to resolve the "fish-eyes" and will severely shorten the life/durability of the paint.

You need to use a wax and grease remover or spirits that are safe to use on the prepared surface to clean or decontaminated the surface before spraying.

Use a tack clothe to remove dust

Wear gloves at all times when handling surfaces to be painting

Remove any silicons from the area (tire shine, armor all, pledge.. anything petroleum based or wax)

You should be able to sand these places out and refinish, however they may come back through. Buy the "fish-eye" additive and have it on hand just in case.


Hope this helps
 
I like to use Naptha to wipe before spraying, between coats, etc.. That's not the gun, but the surface. Good luck.
 
Those are called "fish-eyes"

I sign of surface contamination

Your paint could be contaminated or more likely the surface.

One fix is a "fish-eye" eliminator that the real paint stores have (Sherwin Williams) to use when you are spraying and you see them while the paint is wet.

But this product introduces contamination to resolve the "fish-eyes" and will severely shorten the life/durability of the paint.

You need to use a wax and grease remover or spirits that are safe to use on the prepared surface to clean or decontaminated the surface before spraying.

Use a tack clothe to remove dust

Wear gloves at all times when handling surfaces to be painting

Remove any silicons from the area (tire shine, armor all, pledge.. anything petroleum based or wax)

You should be able to sand these places out and refinish, however they may come back through. Buy the "fish-eye" additive and have it on hand just in case.


Hope this helps

That is perfect, exactly what I wanted to know. I wiped the area down with a tack cloth prior but that wasn't right before I sprayed so I probably had some dust in the area. I also didn't wipe the surface with Naptha prior to spraying. I will be sanding this coat down and respraying tonight, I'll post my results.


I like to use Naptha to wipe before spraying, between coats, etc.. That's not the gun, but the surface. Good luck.

Thanks Mr. Cuda, I will definitely follow that advice.
 
Like others said it could be a dirty surface. To make sure it's super clean and grease free do this 1st clean with simple green to clean dirt and any grease and oils off 2nd clean with with denuetrlized alcohol to remove the residue of the simple green 3rd use a tack clothe to get any dust off 4th spray a very very light coat on to ensure adhesive of the other coats, this is often called a tack coat. It is also a good idea to wear nitrile gloves(looks like latex almost) this ensure no oils from you hands will touch your painting surface when you move it after cleaning
 
That is perfect, exactly what I wanted to know. I wiped the area down with a tack cloth prior but that wasn't right before I sprayed so I probably had some dust in the area. I also didn't wipe the surface with Naptha prior to spraying. I will be sanding this coat down and respraying tonight, I'll post my results.




Thanks Mr. Cuda, I will definitely follow that advice.

You might end up sanding, shooting another coat on that, even after wiping it clean, and getting those same fisheyes. If the original fisheyes were actually caused by tiny pinholes in the jacked up finish, it might do it again. It's like the paint repels away from the pinholes in the finish. I've had that happen. In that case, you'll have to strip it back down and start over. Good luck, maybe you can just sand it flat, wipe with Naptha, tack rag to remove the dust, then shoot another good coat on it.
 
You might end up sanding, shooting another coat on that, even after wiping it clean, and getting those same fisheyes. If the original fisheyes were actually caused by tiny pinholes in the jacked up finish, it might do it again. It's like the paint repels away from the pinholes in the finish. I've had that happen. In that case, you'll have to strip it back down and start over. Good luck, maybe you can just sand it flat, wipe with Naptha, tack rag to remove the dust, then shoot another good coat on it.

I am hoping so. I have two good primer coats down prior to laying the oil paint down that didn't have the Fisheye problem. I did spray a canned primer, two coats, prior to starting the paint work. I laid down one layer of oil after the primer coats but I had a run so I sanded the surface back down. I just laid this coat last night but it was a very light coat compared to the previous coat. I'll sand the fisheyes back out and hope for a different result this time.
 
Like others said it could be a dirty surface. To make sure it's super clean and grease free do this 1st clean with simple green to clean dirt and any grease and oils off 2nd clean with with denuetrlized alcohol to remove the residue of the simple green 3rd use a tack clothe to get any dust off 4th spray a very very light coat on to ensure adhesive of the other coats, this is often called a tack coat. It is also a good idea to wear nitrile gloves(looks like latex almost) this ensure no oils from you hands will touch your painting surface when you move it after cleaning

For the tack coat, do I need that to completely dry before spraying more coats or am I just looking to see if more fisheyes appear?
 
For the tack coat, do I need that to completely dry before spraying more coats or am I just looking to see if more fisheyes appear?

Ideally you would want it dry, a very light coat should be dust free dry with 5 mins, but I also use automotive grade paint so oil based might be different . The ideal air pressure you wanna set it on is 28psi. Are you using a water evaporator? Also there should be a knob in the gun to turn the paint flow down or up so you shouldNt need to mess with the psi to adjust the paint flow
 
Ideally you would want it dry, a very light coat should be dust free dry with 5 mins, but I also use automotive grade paint so oil based might be different . The ideal air pressure you wanna set it on is 28psi. Are you using a water evaporator? Also there should be a knob in the gun to turn the paint flow down or up so you shouldNt need to mess with the psi to adjust the paint flow

The oil base paint takes up to 24 hours to dry which is killing me, I so wish I could spray auto urethane. I do have a water trap on my compressor:

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Nothing on the gun though but I just bought a few disposable moisture traps that attach to the gun itself. What you see above is what I'm using minus the second moisture trap attached to the coupling, that is for my airbrush.

There is a fan pattern adjustment and there is a knob at the back of the gun that is supposed to adjust the paint flow. I have been setting my compressor output to 60psi and then adjusting it down on the gun. Luckily the gun has a pressure test on the trigger so I can partially pull the trigger and check my air pressure at the tip of the gun. I need to spend some more time playing with the paint flow.

I never found good guidance as to what pressure I should have the gun set to at the tip so thanks for the 28psi recommendation. I sprayed at one time at 40psi which was fine I just had to make sure not to stay in one place for too long. 20psi seems to not put down enough paint from what I could tell.
 
Also I do drain the tank after every use and I partially fill the tank and empty it again to remove any moisture that might be at the bottom. I do clean the moisture trap often as well.
 
Here is some good info on properly setting up an HVLP gun.
http://www.hotrodders.com/articles/spraygun.html

Good link. So here's a question, based on this site the inlet pressure is set to the rating on the gun, for example my gun specifies 40psi. I thought the 40psi was what the gun would handle when you pull the trigger. So does that mean that I need to set the pressure at the gun to 40psi or is 40 the max I should see when I pull the trigger?
 
Based on the article it sounds like the sprayer nozzle has it's own adjustable regulator to regulate the 40 psi supply to ~10.

A guess, yeah, I know. Someone else can verify who owns one.
 
Good link. So here's a question, based on this site the inlet pressure is set to the rating on the gun, for example my gun specifies 40psi. I thought the 40psi was what the gun would handle when you pull the trigger. So does that mean that I need to set the pressure at the gun to 40psi or is 40 the max I should see when I pull the trigger?

Set the pressure at the gun while pulling the trigger.
This article goes into better detail on setting air pressure using the valve on the gun.
Your gun might be a little different but should have the air valve on the bottom of the handle. If not then just pull the trigger and set pressure.
My gun has a separate regulator on the inlet for the gun.
I set pressure to 90psi at compressor and about 35psi at the gun.
My gun operates from 20-51 psi so I go as high as I can without blowing the paint off the surface,generally around 35psi.

http://www.purplesagetradingpost.com/sumner/techinfo/HVLPspraygun.html
 
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Based on the article it sounds like the sprayer nozzle has it's own adjustable regulator to regulate the 40 psi supply to ~10.

A guess, yeah, I know. Someone else can verify who owns one.

No the 10 psi would be at the tip.Most guns come with a regulator on the inlet connector on the gun. If not I would put one on it.
To be legal and still retain the benefits of HVLP,you shouldn't exceed the psi rating of your gun.
For home use I wouldn't worry about going over though.
 
You mentioned thinning with naptha.....Rustoleum used to specifically state to thin with acetone . I know the paint companies have been recently changing their formulas for EPA regulations.....I don't know if Rustoleum has changed their formula or not. Might want to check the thinning recommendations on the can (if you haven't already done so).

Edward
 
Set the pressure at the gun while pulling the trigger.
This article goes into better detail on setting air pressure using the valve on the gun.
Your gun might be a little different but should have the air valve on the bottom of the handle. If not then just pull the trigger and set pressure.
My gun has a separate regulator on the inlet for the gun.
I set pressure to 90psi at compressor and about 35psi at the gun.
My gun operates from 20-51 psi so I go as high as I can without blowing the paint off the surface,generally around 35psi.

http://www.purplesagetradingpost.com/sumner/techinfo/HVLPspraygun.html

My gun has a regulator on the gun itself and my compressor has a regulator. So the trick is to keep the pressure on the gun's regulator within the spec for the gun you are using when you are pulling the trigger... perfect, that's how I have been doing it. Mine specifies 40PSI and I initially started @ 40psi but recently have been spraying at 20. I'm going to up it to 30psi this go round, getting ready to spray here in a couple of minutes wish me luck :)
 
Well it went better this time but I think I can still see some fisheyes. I took it down to get rid of the fisheyes, hit it with a tack cloth and then wiped it down with Naptha. It went on better this time but I think I can still see some, I will shoot a picture tomorrow morning once the paint has had some time to dry. It looks much better though.

I ran out of the Semi-gloss paint so I used a Rustoleum Satin oil-base paint this go around.

You mentioned thinning with naptha.....Rustoleum used to specifically state to thin with acetone . I know the paint companies have been recently changing their formulas for EPA regulations.....I don't know if Rustoleum has changed their formula or not. Might want to check the thinning recommendations on the can (if you haven't already done so).

Edward

Great point. The can did say Acetone so that's what I thinned the new paint with.
 
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