I've had some success (finally!) with my Fuji 4-stage HVLP setup. I'm spraying latex paint, with the #4 orifice and needle. I thinned the paint with water to get the viscosity per the manual. It took a lot more water than I was expecting it to - as much as one part water to one part paint. I also added Floetrol, albeit not as much as the directions on the container. The final viscosity with water and Floetrol is in range (20-30 seconds through the cup). It didn't take much fiddling with the gun to get a nice, even pattern. I applied several light coats, and waited about 30 minutes between them. The results are great! Except ...
I have sprayed a semigloss and a gloss latex. In both cases, the finish is flat. I read the Floetrol will cause that. Is that the only reason? Does thinning do that as well? How can I get a semigloss or gloss finish when spraying latex paint?
Get ready for some screams from fellow participants on this group. Here's the real skinny, anyway.
You don't need Floetrol when you spray.
Given the quality of today's latex paints, I wouldn't and don't screw with it when spraying.
Let the screaming and teeth gnashing begin.
Floetrol is a plasticizer, and it affects the viscosity and the density of the paint. The reason you are losing your sheen is because the solids in the paint are separating from the resins due to you modifying (goofing up) the paint formula by introducing materials that alter the chemical composition of the latex paint.
This separation isn't apparent when you brush or roll latex material, which is the original intended application of Floetrol. Using a brush/ roller, the paint is not blown apart into droplets then reassembled on the surface of your project when you brush or roll. Also, you amplify this problem of desegregation of the solids when you further thin the materials you intend to spray.
Next, you are not getting enough material on your project if it is dry enough to recoat in 20 minutes. Even if it feels dry, even if it passes the thumbprint test, don't believe it. If it is dry to the touch and and passes the thumbprint, then it is wayyyy overthinned.
Follow the manufacturer's MSDS or application instructions when applying, as it is their product. There are plenty of coatings you can create your own installation techniques to use as you see fit, but latex paint isn't one of them. The cheap paint isn't worth the bucket it comes in, and the good stuff is a wonder of modern science.
Last, I am thinking that you are setting up your gun wrong to spray latex. I have the same exact Fuji setup. I don't thin latex nearly that much when spraying. Try turning down the flow to the aircap, and turn up the pressure as a first adjustment. Latex will not spray like a solvent based finish (which is almost atomized), and essentially, you are throwing droplets with your HVLP gun when you shoot latex.
This means you have to get enough latex material on the project to maintain a wet surface long enough to lay out properly (20 minutes won't do it). Remember, latex does not resolvate, so to get the proper end finish "off the gun", you have to let the latex dry and contract to form the surface tension that will pull out the anomalies in the finish left by application such as stripes left by inconsistent application, brush strokes or roller marks.
Drop the Floetrol when spraying. Check this out:
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you need to know about Floetrol is there.
Toss out your Ford cup and get out your measuring devices. That thing is supposed to be a guideline anyway, not the final word on material viscosity for application. Measure by volume, not by hit and miss to get you material to go through the cup. To start, thin the paint by about 10%, stir well, then shoot some test pieces with different gun adjustments. Allow your test pieces to dry so you can see what the layout will actually be. On a primed surface (even though it will appear dry) this could take 2 hours. Keep good notes about settings on the gun as well as how much you thinned, and how much material you applied in a pass.
As a sidebar, I took a file and marked each knob on the gun with a notch at 12 o'clock when completely closed. So when I shoot a certain kind of paint, thinned a certain way, I can pull out my notes and open the knobs accurately by registering the turns as I adjust.
Back to the problem. Didn't get it done? Try it thinned to 15%. Keep going until you get the proper gun setup and viscosity, but not thinning more than 30%. 30% isn't good at all, but if you go more you are in serious danger of ruining your paint. If I had to thin that much, I would change brands.
I have thinned as much as 30% for one of those damn gel paints, but it wasn't a good material to spray (I think it was a Ralph Lauren paint). IF your gun is set up properly, and you have to thin more than about 25 - 30%, you need to change paints.
I have shot semi gloss/full gloss enamels out of my Fuji in Sherwyn Williams brand, Coronado, Behr, and Glidden. Glidden was the dirtiest paint, but I think it may have been a bad batch. I am always suspicious of it though as it is the only remaining clay base latex paint out there, the rest being XXoxide, depending on the manufacturer. The Glidden paints are a joy to shoot out of my airless, though.
Remember that no two paints will spray exactly the same, and the devil is in the details. It's that last 10% of figuring out exactly how to apply a finish that makes the 90% of what people see worth looking at on the finished product. Buy yourself a gallon of the brand of paint you are working with and take it out back and experiment with it. It will really pay off in the end.
Damn, Robert ... we're almost there. Just a few more posts like this and my book on spraying will be finished and all I'll have to do is to actually buy a spray rig for appearances.
Is there a tradeoff here? Thin the material enough to spray, apply it thick enough on each pass and give the applied coating time to properly cure, vs. having too much material on a vertical surface and have runs/drips?
I was using Behr and Benjamin Moore paints, which I _think_ are well regarded. I don't recall seeing any thinning or spraying instructions on the cans, but I'll don my glasses and check again. And I'll see if they have anything posted on their websites.
I am not reducing the pressure at all. The air control valve isn't even in my setup at the moment. The aircap adjustment is maybe a turn or turn and a half back from full stop. Any more and I get blobs instead of spray. In general, and as a starting point, would I need to open that up more or less for a less thinned paint?
Thanks again for taking the time to write all this down, Robert. Much appreciated. I'm off to the shop to play ....
Robert, I don't spray and really have no desire to spray but damn you make the process interesting and educational. Thanks for all the detailed explanations that you have given us/ME in the past.
LMAO! Excellent! And your friends will say, "damn.... that Karl really knows how to keep his equipment... did you see how CLEAN his spray rig is?" That in itself will be impressive.
Yeah... what's up with that? It is hard for me to believe I can convince myself that I need another gun... yet it happens.
And they are so damn affordable now it is almost like catching a disease. We can all buy a good pressure guns (even a CAS HVLPs) for less than we used to buy the needles or packing kits for the old high pressure guns.
I am keeping the count under 10, though. Even if I have to sell/give one away!
Thanks, Leon. You know, one of the things I found interesting about finishing was the fact that it is MUCH more than it appears to be. And now with all the new technical/industrial finishes out there it can be quite interesting.
Sometimes I laugh at myself because I feel like Dr. Frankenstein when mixing and spraying, but in the end, all the work is usually worth it.
replying to nailshooter41, Climber5ap wrote: I'm new to spraying, I have recently gotten a Vaper gun from northern tool with a 2.3mm nozzle. I am trying to shoot a glidden paint and primer semi gloss for trim work and interior doors. I have been thinning it about 20% with windshield washer fluid and the gun is spraying it well. I have 2 issues, the first and most annoying is that when it dries, it looks like a satin at best. The second issue is that the finish is rough, but I have a feeling that is more technique than anything else. I would love some input as to why I can't seem to get a good semi gloss finish!
Robert is sure to pipe in (and I always call him for advice when I have less than satisfactory results with my own paint efforts), but one of the things I've learned to first try is using "gloss" for all the base coats; and your preferred sheen (in your case, semi-gloss) only on the final coat.
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