Mixing/spraying paint

Code54 · Jan 10, 2012

I recently purchased a HVLP spray gun, inline filter, gun water filter and all the little things to attempt to learn to paint. What I am not too sure of is how do I learn the proper way to thin paint to spray it. I was playing around tonight and thinned the paint (Valsar tractor and implement paint) 1:8 as the can said. What I noticed is it seemed very thin and the gun was surging when I was painting so I know it was not correct. Is there a standard mix out there and/or a mixing chart somewhere? Also what causes the gun to surge (sprayed fine but would spray, pause, spray, pause, etc...)
Thanks and any info on spraying paint is helpful because I know absolutely nothing.
Oh the compressor is an IR 80 Gal, 2 stage, 24 CFM, so air flow should not be an issue (at least I think....)

JimRB · Jan 10, 2012

You mean 8 ounces of naptha for a gallon of paint and some hardener?

JimRB · Jan 10, 2012

Follow up. A few years ago I mixed some Valspar implement paint according to the directions on the label and used a cheap gravity feed HVLP spray gun. It sprayed nicely. I do not have any empty or partial cans to read the mixing instructions. I used a much smaller compressor. A 20 gallon tank or so Binks pump.

Here is an article that is interesting. Good Stuff! | Amateur radio - Teardrop trailers, Vintage Shastas, Martin Luther Miller, TN and more

JimRB · Jan 11, 2012

Another follow up. You can get mixing cups that have the mixing ration on the side. You dump so much color in, add the thinner and then some catalyst. Paint Mixing Cup Set 13 pc
Video that explains the mixing cup
[ame=http://www.youtube.com/watch?v=nbywJIEYNfQ]Auto Painting : How to Mix Auto Paint - YouTube[/ame]

ETpilot · Jan 11, 2012

For mixing paints you need to follow the manufacturers recommendation. It will be on the can. Different paint systems mix in different quantities. Some just add thinner, others add thinner and hardener. I mix an aircraft paint, 3 parts, by weight in grams.

As for the spray gun surging, that is usually an air leak in the gun. Most often it is the fluid nozzle that is not tight enough. Look at your gun manual. It may list a torque value for the fluid nozzle. The fluid nozzle must have a good seal. Also the packing for the needle and air valve need to seal. Usually you add a little oil to the packing. Again check the gun manual.

After use do a thorough cleaning of the gun.

murphy1244 · Jan 11, 2012

After use do a thorough cleaning of the gun.------He ain't kidding about that.
If your pulsating you have a air leak. I shoot at around 40psi with my devilbliss.

Rustywreck · Jan 12, 2012

It has been awhile, decades in fact, but when painting cars I used a viscosity cup. The paint can had a viscosity number on it and you used a viscosity cup to measure if additional thickening or thinning was needed.
I haven't looked at an automotive paint can in a long time so I don't know if that system is still used - it worked pretty well.

flusher · Jan 12, 2012

Rustywreck said:
It has been awhile, decades in fact, but when painting cars I used a viscosity cup. The paint can had a viscosity number on it and you used a viscosity cup to measure if additional thickening or thinning was needed.
I haven't looked at an automotive paint can in a long time so I don't know if that system is still used - it worked pretty well.

A VC came with the Harbor Freight HVLP gun I use to paint my old, restored tractors.

Code54 · Jan 12, 2012

Great information, thank you.
As for the gun, it is from about 1991, and had not been used since then so the idea of an air leak sounds spot on. I also have a brand new gun but did not have the fittings on it yet so I figured I would use the old one - guess I better get the new one out and start practicing mixing paint.

woodlandfarms · Jan 13, 2012

One additional question. Do you need to put any sort of dryer or something like that on your tank line? Or is paint now pretty much immune to those issues?

If so, what kind of drier are people using. Again, I am keeping this in the vein of tractor painting, not precision auto.

Carl

Sutol · Jan 13, 2012

woodlandfarms said:
One additional question. Do you need to put any sort of dryer or something like that on your tank line? Or is paint now pretty much immune to those issues?

If so, what kind of drier are people using. Again, I am keeping this in the vein of tractor painting, not precision auto.

Carl

You can get a water trap to put in the feed line.

But I just drain the compressor tank of water before I start.

Soundguy · Jan 13, 2012

after a while you will get a feel.

IMHO.. if it sprayed, paused and sprayed, you either have low air pressure.. or too viscous of paint.

OI thin my valspar and dip the stem in and watch it drip off.. and then I used a test piece of metal before I ever lay down color on a tractor.

give it 10ys.. you'll be fine!

Soundguy · Jan 13, 2012

also.. run an air hose that has not had oil running in it from an auto oiler...

Code54 · Jan 13, 2012

Thanks - I know my pressure was set at 40psi (as per the guns instructions) so the mix may have been off. I never even thought about water - funny thing is I have one line with 2 air dryers (mainly for the blast cabinet) but hooked to the spare output with no air dryer (that was dumb on my part huh)
10 years huh, wow, I better get busy, I was hoping to paint a Cub by May so I am going to have to kick it in HIGH gear!
Thanks for all the help and information

Soundguy · Jan 13, 2012

water won't cause the start / stop. it will blow a mess out on the paint.

I'd 'guess' you air may be a lil low.. try 50, and or check the thinning..

I have seen 'cheaper' hvlp need about 20% higher pressure than rated for.. just my observations.. and I paint near exclusively with valspar paints.. though have switched over a bit to nason syn enamils and quick dry hardner...

Code54 · Jan 13, 2012

Will do, thanks!!!

strum456 · Jan 13, 2012

Like soundguy said, it sounds like low pressure or thick paint. When you set your pressure regulator, did you set it while pulling the gun trigger? If not, that is your problem, guranteed.

It has been a couple years since I bought any valspar, but I distinctly remember having to experiment with my thinner ratio because there was none recommended. I think I ended up around 5 or 6 parts paint to 1 part thinner.

How to set up your paint gun:

1. Look for the manufacturers recommended PSI, distance from panel and fluid tip size for material to be sprayed (set accordingly).

2. Set your fan how you want it, (all the way out or very close to it for all overs.

3. Crank the fluid knob all the way in and then back out one turn. Hold the gun perpendicular to some making paper on the wall at the recommended distance (usually 6-8 inches) and snap the trigger. Your pattern will probably be small and narrow in the center. Turn the fluid out in half turn increments until you get an even pattern and a nice wide fan.

4. Now, go to somewhere lower on the vehicle out of direct view and make a test pass. You will probably need another 1/2 turn or so out to compensate for your rate of movement (should be about a foot per second).

5. Fine tune air and fluid. If you are getting a few runs, increase your air pressure by 5 psi or more. If you are getting heavy peel, turn in the fluid a 1/4 turn at a time. Of course, this only works if you are doing everything else right :thumbsup:

6. Maintain constant speed and distance when spraying. Overlap atleast 50%.

7. Readjust your gun each time you use it. Different paints require different settings. ALWAYS check your spray pattern on making paper first. ALWAYS!

LWG · Jan 13, 2012

You almost always needs a water separator, depending upon the humidity of your shop. There are water separators that are meant to be placed close to your compressor, and smaller ones that are meant to be placed right before your gun.

strum456 · Jan 13, 2012

woodlandfarms said:
One additional question. Do you need to put any sort of dryer or something like that on your tank line? Or is paint now pretty much immune to those issues?

If so, what kind of drier are people using. Again, I am keeping this in the vein of tractor painting, not precision auto.

Carl

Paint is definitely not immune to air line moisture. Moisture can result in fish eyes or bubbles from trapped moisture under the paint.

To do it right, an air dryer and the plumbing is quite pricey. You can make a low budget air dryer by coiling some copper tubing (best) or an air hose (works ok) in a bucket of cold water. Keep in mind, a water separator will not work if the air is still hot from being compressed. The air needs to cool before hitting the separator, so the moisture can condense. So, the cold water helps with cooling. If you have a properly designed plumbing setup, you wont need the bucket. No matter what, you want your seperator as far from the compressor as possible. 50 feet or more is best. For painting, you should really have a sub-micronic final filter also. Mine is a motorguard m-60. It is a very well built unit.

Don't rely on those little filters that go before the gun. They lack sufficient capacity to be used as anything close to a stand alone filter.

Code54 · Jan 14, 2012

THANKS strum456 - your right, I set the pressure but NOT while I was pulling the trigger - never gave it a thought. Also your how to set up the gun is great - I am going to do that. Actually I printed that part out and am going to stick it on the inside of my paint cabinet!