Spraying primer with HVLP gun, What am I doing wrong? Options

[bondo]

Ok, I tried out my new HVLP gun. I was spraying high fill primer. The output was similar to what you get from an airless sprayer for house paint. It literally looks like an orange.

Here are a few things that could be contributing factors:

1. Never used a HVLP gun before
2. 3 year old primer that says "use within 6 months"
3. Cheap Harbor Freight spray gun (no instructions besides an exploded diagram)

The primer had settled out and needed serious stirring. I did get it mixed, but it seemed thick. It said thinning wasn't necessary, but after I thinned it a little it worked better, but it still wasn't "flowing out". I didn't want to overdo it and get runs.

This is the gun I have
HF HVLP

I did like how I could spray outdoors in the wind without mega-overspray problems.

[skline]

50 to 70 pounds isnt really an HVLP, I just picked up an HVLP that only requires about 14 to 26 pounds. It also was less money and has changeable tips. For Primer, I would use a 1.8 tip, for color coat I would use a 1.3 to 1.4 tip. Primer when it gets old gets really hard to shoot. Most of your problem is the fact the primer is old. It will setup even without a catalyst. Once it is opened, it must be used pretty soon or it will start to harden.

[skline]

This is the HVLP gun I just got on Ebay for $39.00 delivered to my door in 2 days. It even came with the regulator.

[bondo]

QUOTE (skline @ Apr 18 2005, 07:13 PM)

This is the HVLP gun I just got on Ebay for $39.00 delivered to my door in 2 days. It even came with the regulator.

Does that guy hold a quart? What brand is it? Let us know how well it works. I'm intrigued by the gravity feed.. one of my screwups was touching the can to the fresh paint (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

The box said it takes 50-70 PSI which is "internally regulated". Not sure if I believe that. It definitely is much more HVLP than my regular spray gun, which seems to put half the paint in the air (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[TheCabinetmaker]

Scott. make sure you clean that gun very well after each use, remove the cup and lid, and store them in a sealed bag if you don't use them on a weekly basis. The lid will become stuck to the cup, and you'll crack it when trying to unscrew it two months from now. I replaced three of those crappy lids, then tossed the plastic shit and got a stainless cup and lid. I'm a happy painter now. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[TheCabinetmaker]

Bondo, I know what the ad says, but that ain't an HVLP gun. Thats a VGA suction gun. It uses air pressure to suck the paint to the air cap

[bondo]

QUOTE (vsg914 @ Apr 18 2005, 07:28 PM)

Bondo, I know what the ad says, but that ain't an HVLP gun. Thats a VGA suction gun. It uses air pressure to suck the paint to the air cap

Ok, cool. What does VGA stand for? Can I paint a car with it and get decent results, or should I just ditch it and get a "real" HVLP gun? (I know "the right thing to do" would be to buy a $300+ HVLP gun from an autobody supply, but then I wouldn't be able to afford paint) (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[MarkV]

I have an old Harbor freight gun similar to the one in your link. The material knob on the gun has to be turned way down on mine to get it to spray well. Also, primer has a lot of solids and has to be reduced more than regular paint.

[TheCabinetmaker]

Well, I really don't remember what VGA stands for. Its been several years since I've owned one. The ones I've had worked fantastic when hooked up to a 5 gallon pot, but that quart cup with the plastic hose on the lid sucks rocks. For non professional use, Skilnes will do what you need, and $39.00 is dirt cheap

[CptTripps]

I've got the 'mini' version of skline's gun...works well for paint...REAL bad for primer. (Ask how I know)

I'm going to HF tomorrow to get a little better gravity feed gun. I can manage a hose, or a can, but not both! I also want to see if there is an elbow I can buy so the air hose is pointed out back, instead of down!


We're going to see how shitty this one is..

http://www.harborfreight.com/cpi/ctaf/Disp...temnumber=47484

[TheCabinetmaker]

90 degree swivel should work.

[J P Stein]

I have an HVLP gun.....8 PSI at 50 CMF turbine compressor...nice warm dry air. Unfortunately it is a pressurized cup and the cup gets in the way. Neither of the guns I got for my paint job work as well...gravity feed. Both are low pressure guns that don't atomize worth shit.
I shot the last few bits with the HVLP gun and it was much better and ya don't have to worry about shittage from your compressor.....live & learn. I could not find a better gun to go with the turbine compressor.

[skline]

This is my 3rd gun like this, they work actually very well when they are new. This gun is only for primer, when I go to shoot the color coat, I will either use a Sharpe or a Devillbis gun. I have used these for color coats but as a rule, they are only good the first time you use them. Once the gun is cleaned they never work as good. So I will use this one for primer as it has a 1.8 mm tip which is perfect for high solid primers. When I do the color coat, I will use a 1.3 or 1.4 mm tip which is best for the actual paint which is thinner.

[RON S.]

QUOTE (skline @ Apr 18 2005, 06:13 PM)

This is the HVLP gun I just got on Ebay for $39.00 delivered to my door in 2 days. It even came with the regulator.

I got the same HVLP gun as Scott,got it also from Harbor Freight for about 50.00 bucks.
It was my first lp gun after years of using regular guns.Here's what I found out.

1st,the pressure setup,and paint mixture is everything.10-12psi at the gun is all it took to make it work nice.No more,less make everything blotchy.Bottom screw on the gun adjusts the atomization.keep adjusting it and try spray patterns on a test panel to get your feel for it.

Using old primer will give you a poor result.BTDT a couple of weeks ago,trying to save some $'s using someones donated primer on a door on my old truck.New pain and primer will make a noticeable difference.

The paints also need to be thinned correctly as per instructions on the labels.These guns are finicky about that.
Air temperature also matters,I've had poor results in cooler weather,50-60 deg,than in warmer weather,70-80 deg.
Either way,if your doing basecoat,clearcoat color sand the finished car and buff it out.Noone'll know it was a backyard paint job then.It's a lotta work,but it'll save a lotta $$$$.


Ron

[MecGen]

Hi
Primer is too old chuck it, if not you will be re-sanding for hours. I shoot at 25psi, 1.4 tip, thinned hi build. Your presure and gun set-up sounds like you are going to get the Aero effect, foam/frost. Very undesirable for a hi build primer.
Later
Joe

(IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[jasons]

It looks like you are getting good advice on gun setup. The tip you use and pressure are definitely important.

I would like to add though, high build primer should have some orange peel. I don't think that should alarm you too much. You are supposed to sand the high build with 220 until the car is straight. Once you start sanding, the orange peel will go away. Its called high build because it has big material in it to fill minor imperfections. That material will create clumps and cause orange peel. That is also why you need a large tip for your gun.

Do you know about blocksanding with contrasting color coats? That is how you get your car razor straight. You will probably shoot the primer 3 or 4 times before you are done if you are blocksanding the car.

[MecGen]

Jasons
Can you explain your technique ?

QUOTE

Do you know about blocksanding with contrasting color coats?

Sounds interesting
Later
Joe

(IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[iamchappy]

Spray tip could be one of the problems but also the distance that you are spraying from, watch a professional paint and you will see that they cut back the gun quite a bit, and spray close to the work area as to lay down a nice wet pattern, the secret is distance, gun pressure and speed. Time is money for them and sanding takes time.

[jasons]

Sure, if you shot a gray primer take a can of cheap black spray paint and lightly dust the car with paint. You don't need alot of coverage just a dust on the car. Once it dries, get a "longboard" (not of the surfing variety) with I think 220 grit to sand the primer/contrast coat. You can get a good longboard and sandpaper for it at any good bodyshop supply place. Ok so once you have the longboard start sanding in an X patterns on the panels.

Reason for the X, if you go too vertically or horizontally you will put waves in the panel. The X pattern straightens the panel. Example, if you are doing the door, start at the top-right of the door and sand towards the bottom left for a few strokes, then move to the other corner and swipe towards its opposite. Vary the pattern, and just avoid horizontal and vertical strokes. You will find places that it is unavoidable, but on the big panels you will be OK. It is also OK to cross the door gaps because that helps make the car contiguous. Also, I hold the longboard parallel with the contour of the car. On a 914 the longboard would be parallel with the ground while sanding the X pattern on the door/fenders/quarters.

Ideally you will just wipe the contrast coat away revealing a perfect panel. Reality, you will find low spots where your contrast coat didn't wipe away, and you will find high spots where you burned through the contrast and probably the primer. So now your car looks a little like a dalmation. Better to find it now than after its painted. Low spots are easy, you can either fill with body filler if they are really low, like a missed door ding. Or, you can give them a heavier dose of the high build primer when you re-shoot if they are shallow. High spots are trickier, depending on the severity, you may have to go back and re-work the panel. If they are minor or you are willing to live with them, build the area around them with a heavier dose of primer and try to fan them out into the rest of the panel. Repeat this process about 3 times and you will vastly improve the prep on your car. BTW, you should use a longboard as much as possible while doing the body filler too. That will cut down on the work you do in the primer stage.


I got alot of help from this site... Lots of valuable info in the knowledge base

http://hotrodders.com/kb/body-exterior/articles.html

The front page

http://www.hotrodders.com/

[Kargeek]

You can thin the primer a bit using acetone...and use a larger tip. DH