The Stovebolt Site Forums The Shop Area Paint and Body Shop HVLP Guns

It an HVLP very different from a conventional gun from the user perspective. I have an HVLP and a standard gun. I bought them as a kit recently. I have used standard guns in the past with good results.

I tried painting with my HVLP gun last weekend and what a mess I have to clean up. I should have practiced more but hind sight is always 20 /20.

I never used a gun air control regulator. I did not realize that the regulator can only be set to 0 or 40 but must be adjusted to 40 while the trigger is pulled. (not mentioned in the directions) So to start off not enough air flow.

It seems that now that I have the gun adjusted properly. I have very little leeway between drips and runs and not enough paint with a sliver of good coverage in the middle.

Should I try the conventional gun?
Am I just out of practice?
My gun was cheap but I have used cheaper with much better results.
Is the gun to blame?

I have a bout a solid week of sanding to comtemplate my over zealous paint experience. 5 years working on thei truck and 2 months of painstaking detail on the body work only to cover it with what looks like hammer coat...what a shame :mad:

PS... anyone want to come to my house for a sanding party this week?

It is real fun...I have sanded this truck for so long it seems like a career.

20 years ago I would have been there. I used to live in Peacedale.

That sounds to me like you had too much air pressure. I run about 25 lbs with my HVLP.

What size tip is it? A lot of inexpensive HVLP guns have large tips because they usually wind up doing primer duty. I believe a 1.2mm or some such is a good choice for top coats where a 1.8mm is good for high fill primer. I have no trouble shooting top coat with a 1.0 tip on my el-cheapo detail gun.

My numbers may not be precise, my guns are hanging in the garage.

The paint tech sheet says 1.3 to 1.7 for this urethane.
I have a 1.4

Well, then we know you have that correct. Now let's concentrate on correct adjustment of both the gun and your technique.
LINK TO HELP

Thanks Woody,
That was helpful ...as was the tech tip righ on this sight.
I was just to impetuous to stop and learn to do it right. I had the body of the truck in better shape than when it was new....best body work and sanding I have ever done.

Live and learn.
Rich

Tmater

Thanks for the advice. I think I had the air way too low and the fluid volume way too high. When you say 25 lbs do you mean at the gun with the trigger depressed. I read somewhere ot set the compressor presure to the max gun pressure and then adjus the inlet pressure witht he trigger depressed. One site said pull the trigger enough to get air and no fluid out of the gun and then adjust the pressure.

How do you do it?

I am going to work with this gun on the back of my old steel cabinet tool box till I get it right. May as well have the tool box match the truck

At least that is flat if I have ot sand it all off and do it again.

Rich

Yes, set the air pressure with the trigger depressed.

Thanks Woody

I thought this would be the fun part.....

Every thing you've done, all the work, blood, sweat and tears will be long forgotten but your ride will always be judged by the way it looks. Personally, I find tasks like sanding to be very therapeutic... lots of time to ponder the universe (c:

I'm sure you'll get it figured out and I'll be waiting for those photos!

Woody,
Your right I did find the sanding to be therapuetic as well...the first 2 times

BTW I love your artwork. Your black and whites are stunning.

Make sure your pattern isnt too narrow. Test panels are your friend!

I tested and adjusted for a few hours last night. I finally shot the sealer on the cab and it looks pretty good this am. Not perfect but about 100 times better than the bed which I shot
last week.

Unfortunately it took so long to adjust the gun it was too late to shoot the color. I will nee dot scuff it up and try to get color on tonight.

My one question is that I seem to have very little fluid coming out the fluid adjustment is only turned out about 1 turn. Air pressure is a abotu 22 to 25 withthe trigger pulled. I did still seem to have some overspray but i was not happy witht he atomization if I turned up the fluid or turned down the pressure. It is epoxy urethane sealer mixed to spec with hardener and medium reducer. Temp was about 65 last night.

Any thoughts?
Rich

Turning up fluid while turning down the air pressure is counterproductive to your desired result. Flow rate is a balance between air pressure and fluid volume and viscosity.

Not being there I would suggest that if you want more fluid and more atomization try increasing both the fluid rate and air pressure or just increase the air pressure. The fluid flow and amount of atomization is driven by the air pressure unless you change the viscosity of the fluid.

Regardless of what kind of equipment you are using you will get overspray, it's just minimized when you use an HVLP gun.

At least that's my take on it. Perhaps someone with more practical experience and less theory will chime in.

Woody,

I think I was unclear. Once I was happy with the atomization it seemed that the fluid volume was very low. I tried incresing the fluid level and pressure to get the same atoization but evenually gave up.

I did paint tonight and I am happy so far with the result. I will see if I still feel that way when I get it out in the sunn after it drys.

What is the best way to get rid of the over spray...color sand or buff. If it is buffing what do I use.

Thanks for the help
RB53

Rich,

Well at least it sounds like you've made big improvements.

As for overspray, first off let's understand what it is. From what you describe you have areas that are not smooth - pebbly or orange peel in appearance. This is the result of the paint going down too dry. In order for paint to be smooth it has to go on wet enough to flow out but not so wet that it runs or sags. This is all technique.

The edge of the fan is dryer than the center so remember to overlap your passes so that each overlaps the previous by about 50%. Theoretically this lays down the same volume at the edge as in the center. With this in mind realize that the drier paint in the air is also settling on the part where you've just painted and areas you have yet to paint.

So the trick is to get an even WET coat on everything so that there is enough solvent to make the paint flow, and again this is all technique which comes from experience and I could sit here all day espousing theory but I'll never be able to give you the experience to perfect your technique.

The only way to get rid of overspray or orange peel is to wet sand the bumps off with like 600 grit or finer grit wet-or-dry and then polish. Scary stuff but if you have enough paint down you won't sand (or polish) through.

Keep us posted.

That is what I thought. This is all technique. My experience with painting in the past was much simpler stuff, equipment and a few small cars.

I found it difficult to stay ahead of the dry edges not due to speed but the complexity of the body lines on these trucks. For instance there is a dry spot on the side of the hood where over spray from the fender did not melt in.

If I painted it 10 more times I might get it down but then my gas mileage would go down due to the paint drag.

I will likely sand smooth and apply 1 or 2 more coats. I only used about 70 ounces of paint for 2 coats on the cab. I might have been a little stingy.

The orange peel I have is extremely slight. I could comb my hair (if I had any) in the reflection on the truck.

oh and I have a few million dust specs but those should come out in the polish.

Yea, I live on a gravel road so I have to wait until after a good rain before I can paint.

You'll want to hit those dust bumps with some VERY fine (1200 grit) wet first. Not sure if you know but adding some detergent to the water helps.

Yes Dawn works best I am told so that's what I use.

Now that I look at the truck in the day light. It is not as good a job as I thought. Not too bad but I will have to sand and recoat. I did polish a little and it came out ok. I am just concerned that there is not enough paint there. I will sand with 400 or 600 and recoat then work the finish.


Then I can get back to the bed.

Ok so I thinkl I have solved the problem. I was too stingy witht he paint. I sanded and recoated and solved the overspray issue but introduced the run and drip issue. I am sure woody is right. It has been a long time since I painted anything.I am working with different materials and different equipment (and also in a very cramped space which is probably not lit well enough for the task.

However, I am pretty sure now that I have enough paint to color sand to a nice finish. I was going through paint about 3 times faster last night.

I will wait a few days to ensure curing and then I will shave the drips with a razor and color sand.

I hope all goes well. Thanks all for the support in this. I was losing my mind for a while there but I will keep sanding and buffing until I get the desired result. Then I will post pics!

Rich

PS...any suggestions on compound and polish. I bought an inexpensive buffer yesterday. I buffed a few of the pieces I had done earlier and had moderate results.

It is a small craftsman 2 speed buffer. I wanted something easy to control. It did a decent job...remember the goal is not a high gloss show finish. I want the truck to look like it has been well taken care of through its hard work life.

Thanks again for all the help.
Rich

As for polishing I can't recommend a polisher but something I can recommend is to be VERY careful around edges and sharp bends on the panels. Those areas (especially sharp bends) will have less coverage and will wear down very quickly.

Trick is to use the polisher in such a way so that the rotation of the pad is spinning away from the edge. This will minimize the amount of pad/compound that contacts the edge.

Another thing is to be sure the nap of the pad doesn't become slick with compound, otherwise it will tend to heat up and literally melt and smear the paint. Back in the day we flipped the polisher over so the pad was facing the operator, turned it on and used a flat bladed screwdriver to raise the nap.

Not sure what compounds you are using but if they don't come in a squeeze bottle you can use one of those squeeze bottles available for dispensing catsup and mustard. You can also dilute the polishing compound with water if you think it's cutting too easily.

Some new pics of the "new" look for my truck.
Lots or orange peel to remove but I have left the 1000 grit scratches in as I buffed for an old work truck look. It looks like the finish I remember cars having when I was young.

I suppose I can just continue to sand to 1500 or 2000 if I don't like this look. I just need to be real careful not to sand through.

I put 2 coats on and then sanded (because of the poor finish) then added 2 more coats. After sanding with 600 (very briefly) and 1000 I really don't know how much paint is left.

This paint job has been a long journey...not what i expected. I was really hoping to be doen at this time but i still have a few weeks of sanding left.

Rich

Pics are on my webshots page in the album titled "Paint"

I got the bed painted last week. It is a little better then the cab. I will be wetsanding and buffing this weekend and hope ot post new pics soon.

I didnt see this mentioned, a conventional and HVLP are two totally different animals. A conventional gun works by air pressure, a HVLP works by air VOLUME a huge and suffient difference.

If your air compressor can not meet or handle the air VOLUME requirement of your gun no matter of adjustment is gonna correct anything.

I didnt see you say what brand of gun you bought. Horror Fright purple guns are Sata knock off guns and are air hogs, they consume huge amounts of air. All Sata's run in the 14-15 CFM range and so do most Sata knock offs.

If your compressor simply can not meet the CFM rating of the gun, you are wasting time, period. Then you need to switch to a conventional gun which operates through air pressure and not air volume.

HVLP guns do not spray paint as fast as conventional guns so you need to slow the speed down. Also, only pay attention to the paint hitting the panel, adjust the speed as the paint lays flat. Paying attention to where you are gonna go is NOT as important as the where you just currently went...Eric

Thanks Eric... The guns says it runs on 5.5 CFM (which seems low for an HVLP) My compressor puts out 8 or 9 at 40 PSI.

I probably should have used the conventional gun form the start but since I am painting in a garage I was concerned about the extra vapor and material in the air and to save paint. I have plenty left over.

I may mix some paint and spray my tool box to see if it is just my comfort with this new technology.

If it comes out great I will be very disappointed that I did not use the conventional gun.

Here are some new pics After many weeks of color sanding and buffing.
Still some work to do but I will be driving in the interum

http://rides.webshots.com/photo/2561234570083206947LKhHsy
http://rides.webshots.com/photo/2549266970083206947qBRkgd
http://rides.webshots.com/photo/2400398100083206947EYelzq
http://rides.webshots.com/photo/2158249800083206947otOZSI

Photos look GREAT!

I just broke down and bought a Finex FX3000 HVLP. Used it this morning to put down some Imron. 1.4 tip.
I`m happy with its performance compared to my old Devilbiss JGA 502 which has to be 25+ years old already.
One thing I should add here which may help others is the fact that you have to spend time tuning in your gun before you start actual painting. A piece of cardboard is invaluable when adjust pattern, atomization and coverage.

I only used a HVLP gun with good results. I stll spray with the conventional JGA gun which I become accustomed to. I have been spraying paint for more than forty years. It took me almost that long to learn that when I thought I was finished spraying I then put down another coat. This my friends made and makes all the difference in the world. By doing this there is a big improvement in the finish and the gloss. By the time I have everything figured out I will no longer feel the need to spray paint. It's too bad I/we can't pass this experience down to the next generation. I suppose they to will need to learn they hard way. :>)