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Discussion Starter · #1 ·
I am trying to figure out the ideal droplet size.

I have a Eastwood concourse HVLP gun and a 4.5 peak HP/ 21 gal., 8.8 delivered at 40 psi.comp.

Air supply is set at 50 psi at comp. Gun regulator is set at 50 psi when trigger is not pulled and between 12-29 psi when trigger is pulled. I have been experimenting with different psi to see the difference in pattern/coverage.

It seems like 3 turns out on the material vol. knob is working best at about 29 psi with the trigger pulled. Air knob is 1.5 turns out.

I have been using these gun set up tips: http://www.stovebolt.com/techtips/hvlp_paintgun_basics.pdf

I have practicing using Mark777 masking paper/tape trick. That masking paper trick worked great when I doing some rattle can spraying to make sure it was the correct time for each coat.

Using the set up tips above, I can get a cigar shaped pattern as shown, but paint is 3 dimensional and the pattern shown on the link is 2 dimensional.
I do not know if my "bb's" or droplets are too large/small.

In my test pattern there is uniform paint coverage, but it always has droplets of paint on the surface. They do flow out as the paint dries.

How "wet" should each pass be? And how many passes should make up a "coat" ? I know there is definitive answer, but a generalization is fine.

When rattle canning in the past my coats have always been rather thin to prevent runs. I then build up coats to get coverage.

It seems that with the HVLP it is possible to spray coats with more complete coverage and the heavier coats allow the paint to flow and get a more uniform, smooth and glossy finish. Am I heading in the right direction?
 

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I am trying to figure out the ideal droplet size.

I have a Eastwood concourse HVLP gun and a 4.5 peak HP/ 21 gal., 8.8 delivered at 40 psi.comp.

Air supply is set at 50 psi at comp. Gun regulator is set at 50 psi when trigger is not pulled and between 12-29 psi when trigger is pulled. I have been experimenting with different psi to see the difference in pattern/coverage.

It seems like 3 turns out on the material vol. knob is working best at about 29 psi with the trigger pulled. Air knob is 1.5 turns out.

I have been using these gun set up tips: http://www.stovebolt.com/techtips/hvlp_paintgun_basics.pdf

I have practicing using Mark777 masking paper/tape trick. That masking paper trick worked great when I doing some rattle can spraying to make sure it was the correct time for each coat.

Using the set up tips above, I can get a cigar shaped pattern as shown, but paint is 3 dimensional and the pattern shown on the link is 2 dimensional.
* I do not know if my "bb's" or droplets are too large/small.

**
In my test pattern there is uniform paint coverage, but it always has droplets of paint on the surface. They do flow out as the paint dries.

***How "wet" should each pass be? And how many passes should make up a "coat" ? I know there is definitive answer, but a generalization is fine.

When rattle canning in the past my coats have always been rather thin to prevent runs. I then build up coats to get coverage.

It seems that with the HVLP it is possible to spray coats with more complete coverage and the heavier coats allow the paint to flow and get a more uniform, smooth and glossy finish. ****Am I heading in the right direction?
Hi Joey,

IMO, If you’re using an air regulator gauge at the gun base, and I’ll assume you are using the standard 1.3mm needle to nozzle for light to medium material movement, you might want to start over. *Try reducing the material knob and increase the air pressure slightly. This will provide you the opportunity to see the minimum coverage, a lighter spray pattern (almost transparent) and the shape, size and width of the pattern on your test panel. A good HVLP gun will deliver huge amounts of material (transfer efficiency) and very little over-spray. Compensating the material amount raises the comfort level and extends the working times during application to your target project. Exploring the gun’s limitations and finding out the minimum and maximum capabilities give you a whole new perspective of what you have and can work with.

**There is very little difference and impact on the droplet size if the paint flows out and doesn’t run or sag. The finer adjustments and viscosity of the paint is essentially for light to medium metallics, which you’ll discover are controllable. Medium to heavy droplets are much better for heavier (high solids) color coats and clears.

***Various stages of “Wet” begin after you’ve used your substrate (Primer/Sealer) and apply the first “Tack” coat. This acts as the adhesive between the primer and the following color coats. Most painters do NOT adjust their gun for the tack coat and leave their gun settings for the following coats. They make their first pass quickly and at the same distance to compensate for the gun settings. Think of the tack coat as Glue instead of paint and apply it quickly instead of trying for heavy coverage. This is often the first and most difficult step that many painters overlook. When they rush or try and bury the discoloration instead of applying a thin tack coat, problems like ‘solvent pop’ surface hours (or days) after the job is done.

(If you use your test panel each and every time before your approach your project):

Once the tack coat has dried sufficiently and you can stick your finger in a masked or taped area and there are no paint strings or smudges that stick to your finger, then you apply the second and third color coats. These following coats are often referred to as ‘Hide’ coats. Using your test panel will dictate the best ‘flash’ times between coats. The final coat should be applied slightly slower than the previous coats. Slowing down will allow the heavier coat to flow out and produce the best results. Another common mistake painters make (and I have made) is piling on the top coat color. More is NOT better. And the results may be beautiful at first… but the problem of solvent entrapment (solvent Pop) rears it’s ugly head soon after you’ve pulled your paper and tape and you assume the painting session is over.

****Yes, you’re right there. I can only suggest that you experiment with your gun controls and air pressure to produce the best and worst patterns. Finding the best on the test panel will produce the same results on you project. I hope this helps...

Mark
 

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Discussion Starter · #3 ·
Mark,

I'll increase the PSI and back off the material. I did a test starting with lower psi and then increasing the material a 1/2 turn at a time and doing a quick on/ off spray. I did the same with higher psi. After studying each spray I saw what I thought was the best coverage, but I can see how higher psi and less material will have more uniform coverage.

The finger test with the tack coat and following coats worked great when rattle can spraying and I will rely on it for this also.

"
Another common mistake painters make (and I have made) is piling on the top coat color. More is NOT better. And the results may be beautiful at first… but the problem of solvent entrapment (solvent Pop) rears it’s ugly head soon after you’ve pulled your paper and tape and you assume the painting session is over
. "

Very good. I really appreciate the info.

Thanks

Joey
 

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Check out autobody101.com they have how to pages, forums and alot of info. Even if you are a beginner, with a bit of reading you'll be able to lay down a very nice paint job. Like stated above, pay attention to flash times and dont rush. The last thing you want is solvent pop and die back due to a rushed job. Spraying methods differ greatly between varying types of paint so be sure to practice on something first to get your adjustments just right. What kind of paint are you spraying?
 
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