HELP NEEDED ON HVLP PAINT GUN

On Fri, 24 Aug 2007 18:46:38 -0500, with neither quill nor qualm, "jusme" quickly quoth:

These guns aren't built for acrylics/latex-based paints, period.

I _warmed_ my paint and used FloeTrol to the limit when painting my bifold/shuttered closet doors with gloss latex and it was right on the edge. It (barely) did the job but I won't use it again for acrylic paint, lemme tell ya. The standard 0.057 (0.054" on my 43430) nozzle is just too small for that thick material.

Count me out on that, but I do try. ;)

-- Books are the compasses and telescopes and sextants and charts which other men have prepared to help us navigate the dangerous seas of human life. --Jesse Lee Bennett

Surface prep on the part?

Thanks, all. I suspected that but wanted expert advice and I got it.

Now, this 15 kw., diesel generator is half done and I want to use a different paint that WILL work in the hvlp AND GO OVER THE TOP OF WHAT I HAVE DONE. Any advice as to what I can use?

Also, do you guys like hvlp guns?

Thanks much.

Grant, that would be quite a trick: sanding the part to stop the spray of globular droplets.

Sorry, didn't want to resist.

HVLP is the way to go with *solvent* based paints - the old high-pressure air paint guns waster too much paint as overspray, the HVLP is moving slower and puts more of the paint on the item and less into the air.

The automotive paint industry must have figured out a way to combine water based automotive paints and HVLP and make it work, because all the environmentalists have been pushing to drastically cut solvent emissions. But I don't know if or how well.

You might try running the water based enamel you have been using through a high-pressure sprayer pump paint system like used on houses. They are often available for rent by the day & week. These Can Not be used for solvent based paints, because between the solvent fumes and the static electricity generated in pumping and spraying the paint there's a serious fire and explosion hazard

If you started with one type paint you'd better stay with it, unless you want to strip the whole job and start over. And remember that little life lesson for the next time...

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You pretty much have to use a pressure feed type paint sprayer to spray your latex paint.

In my understanding, this is how the automotive industry has gotten waterborne paints to work for them. That, and they have the money to throw at LOTS of automated equipment to apply it with, and they still have some issues.

All the HVLP sprayers I have used, ranging from really cheap, to really expensive Italian made guns, had settings in their instructions, that were right out to lunch.

We would do all our adjustments against a paper 'Try' sheet on the wall of the booth, and tweak each setting to get the results we needed.

Most often, that meant way more air pressure, than was considered proper, but sometimes way less, depending on the thickness of the paint. The guns that were set up with different size nozzles, got a bigger nozzle for thicker paint or larger area jobs.

Last time I sprayed latex with a gun, it was an electric solenoid operated thing that made a hell of a racket (Lemmer?). Worked OK, but you had to move fast.

Go rent a pressure sprayer from the Home Depot or other tool rental source. They may even have one that uses plastic bag liners on the paint pot. That eases the cleanup a little bit.

Sort out your work order so you can be ready to push paint ASAP after you arrive, then do touchups ASAP. That'll minimize your time of rental, at least.

Cheers Trevor Jones

Thanks, guys.

Well, I have a 3000 psi airless spray rig and I broke it out and for some reason, it won't pump. Gosh, I have a black cloud overhead.

When used last, I cleaned it to a fare-the-well and pumped paint thinner through it and sealed it up so that it would be ready for me. Not to be. It would build pressure and spray a burst and then stop.

I may have some bad hose on the pump itself. The gun hose is fine.

Anyway, I finished the job with a regular spray gun and high pressure.

What a job.

Thank you very much for all of the help.

Now, I know that hvlp is NOT for latex based paint.

Are professionals really using hvlp for auto painting?

j

I just finished painting my front door with Kelly-Moore Epoxy Enamel using a HVLP gun. The un-thinned paint was very thick - on the order of pancake batter. Initially, as you did, I used the thinning recommendations on the can and got an orange peel finish like you. I have found that to get latex to spray correctly you need to do the following:

1) Use a larger fluid nozzle and needle. My gun recommends a 2.0 mm nozzle for latex. This is what I used.

2) Use Floetrol as recommended by others.

3) The following is the most important. Forget the thinning recommendations on the can. Get a viscosity cup and thin the paint to around 22 seconds. You will be surprised how thin a 22 second viscosity is and how much water you will be adding. The final viscosity will be on the order of milk. If you do not thin the paint it will not flow out on the surface, and you will have orange peel.

When you spray make sure you get a wet surface but don't lay the paint on so thick it will run. If the coat is not wet in will not flow out and you will have a sandy surface. Remember the thinned paint is much more likely to run. Do not try to get one-coat coverage with the thinned paint. Your first coat will make you think you are spraying water and look more like a stain rather than paint. It will take several coats to get a nice buildup but the thin coats dry quickly, and several coats can be applied fairly quickly. Watch the spray gun tip. I got a rapid buildup of dried paint around the nozzle. Eventually the buildup effects the spray pattern or worse breaks free and lands on you work. I just kept a bowl of water and a toothbrush nearby and when the buildup got too large I would hit it with a wet toothbrush. The thinned paint tends to separate quickly so make sure you keep it stirred.

Using the above procedure I got a near glass-like surface on my door.

Good Luck

I just finished painting my front door with Kelly-Moore Epoxy Enamel using a HVLP gun. The un-thinned paint was very thick - on the order of pancake batter. Initially, as you did, I used the thinning recommendations on the can and got an orange peel finish like you. I have found that to get latex to spray correctly you need to do the following:

1) Use a larger fluid nozzle and needle. My gun recommends a 2.0 mm nozzle for latex. This is what I used.

2) Use Floetrol as recommended by others.

3) The following is the most important. Forget the thinning recommendations on the can. Get a viscosity cup and thin the paint to around 22 seconds. You will be surprised how thin a 22 second viscosity is and how much water you will be adding. The final viscosity will be on the order of milk. If you do not thin the paint it will not flow out on the surface, and you will have orange peel.

When you spray make sure you get a wet surface but don't lay the paint on so thick it will run. If the coat is not wet in will not flow out and you will have a sandy surface. Remember the thinned paint is much more likely to run. Do not try to get one-coat coverage with the thinned paint. Your first coat will make you think you are spraying water and look more like a stain rather than paint. It will take several coats to get a nice buildup but the thin coats dry quickly, and several coats can be applied fairly quickly. Watch the spray gun tip. I got a rapid buildup of dried paint around the nozzle. Eventually the buildup affects the spray pattern or worse breaks free and lands on you work. I just kept a bowl of water and a toothbrush nearby and when the buildup got too large I would hit it with a wet toothbrush. The thinned paint tends to separate quickly so make sure you keep it stirred.

Using the above procedure I got a near glass-like surface on my door.

Good Luck

You don't include enough details to give any insight into your spraying problems, but I'll mention a few things..

That setup isn't a HVLP apparatus. All these junk manufacturers and peddlers/distributors know their equipment isn't HVLP, but they put it on the packaging, and in the ads/catalogs anyway, because they know how the U.S. buyers like the buzzwords and high-tech-sounding abbreviations.

You didn't say what the air pressure was, measured at the inlet to the gun with the trigger pulled, not back at the other end of the hose with the trigger released, where it will be higher (unless you're using very high quality air hose with a very large ID).

You didn't say what you think the output capacity of your air compressor is, or what type of compressor you're using. My WAG is that this particular setup would probably spray ordinary solvent-enamel fairly well. The pressure pot delivers the paint to the fluid tip, so it's just a matter of setting the fluid and air flow to get good atomization for a satisfactory fan and coverage rate.

I'm not certain what instructions you're following, but if the fluid doesn't apply correctly because it's too thick, then you're using the wrong equipment, or the adjustable aspects are mis-adjusted. The fluid needs to exit the fluid tip with almost zero resistance and be atomized completely just beyond the air cap. The easiest thing to try is more thinner (water), and try it on some practice pieces, and anticipate that thinner coats and longer recoat intervals, will mean that it's not gonna be just a one-shot deal. This would involve dismissing any expectations of being done in 5 minutes, with results that will amaze and delight.

I admit that I haven't sprayed water-enamel paints. I have sprayed quite a bit of latex, (and my share of solvent coatings) and it's really not a problem to spray thicker fluids with a pressure-feed gun (unless the compressor isn't keeping up).

You may need to accept that the HF rig may only perform as well as a quality touchup gun, and not the ultimate piece of high-tech gear. Heavy-bodied fluids usually require larger passageways for the fluid, and higher capacity air caps (requiring more CFM of air from the compressor).

These are some examples of real HVLP paint guns, and about the only way you'd get one of these for under $100 is if they're stolen.

Notice that real HVLP guns operate at about 3-8 psi, and the turbines are stated to produce 80-130 CFM. That's where the LP and HV come from.

All these flashy, bright-color anodized, low priced guns are just using HVLP to sell ordinary high-pressure guns, that are made as cheaply as possible. Then they suggest/claim that those guns will perform like real HVLP guns do.. save paint, reduce overspray, etc. They were once referred to as conversion guns, when the air and fluid holes were increased, but little else was done to actually increase air flow throughput. It's the fishing lure marketing method.

You could've been posting pictures of your "finished" project already, instead of asking why the paint won't come out of the gun, if you had just used some utility enamel and solvent reducer.. or even spray cans.

You'll probably need to do quite a bit of experimenting with the water-enamel, and maybe need to get gun parts with bigger passages/holes, before you'll be able to determine if that setup will ever give satisfactory performance with the water-enamel. Satisfactory performance to you, is dependent upon what your expectations are.

I know that it's easy to reduce overspray easily with a conventional high-pressure siphon gun, just by folding the air hose over and squeezing it in the other hand, or adding a valve at the gun fitting to reduce the air delivery. A well-made siphon gun will still lift the paint up to the fluid tip and atomize it well, even at reduced air flow.

If I ever get around to trying any of the newer water-type finishes, my guess is that I might have a lot to say about them. I imagine it's very different than the solvent coatings I'm accustomed to. I would think that using water in a production situation would require some specialized equipment and a controlled environment to attain any sense of consistent results.

WB ......... metalworking projects