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Feb. 26, 2011 9:36 p.m. former520 New Reader

Today I shot the bed of my truck in a polyurethane single stage black and got massive amounts of orange peel. I was using this Advantage brand product, which the paint shop said was a decent, inexpensive paint. http://www.advantagerefinishproducts.com/

I was using the Harbor Freight gun that comes with the pressure regulator at the handle. I was using a 4:1:1 ratio of paint, hardener and thinner as recommended. I called the paint store after I was having trouble and upped the thinner to 2 parts.

At first the paint was coming out like texture from a drywall hopper gun, it was smaller pieces of paint coming out when thinned more, but still isn't coming out fluid. I tried a couple different pressure settings, they recommended higher, so I stayed around 40-42 at the base which should be 6-8 at the tip. I also tried playing with the fan size and paint volume. Couldn't find a sweet spot.

Anyone have any ideas to try or good methods of tuning the gun? I did the bed first and it is easier to sand. Tomorrow is the cab and I am hoping for less wet sanding.

Oops... weather. It was slightly wind (painted in driveway) 64-66 degrees outside, varying between cloudy and windy.
Feb. 26, 2011 10:19 p.m. ww SuperDork

Sorry, there's almost no way you're going to get even atomization out of that HF spray gun no matter how good your paint is or how much you try to tune that gun. It just isn't capable of anything better than old farm equipment quality.

Here's a good place to start if you want to be able to lay down a decent coat of paint on a car. It's still not the best but it should be passable where the HF guns are complete crap. I will admit, I use the airbrush but that's about it.

http://search.eastwood.com/search?asug=paint+guns&w=paint+guns&p=Q&ts=...
Feb. 27, 2011 7:04 a.m. digdug18 HalfDork

Yeah, some of the HF guns are very good quality, especially compared to far more expensive HVLP guns. This on is item #66222, better then eastwoods' gun as well.

As for what your doing wrong, its more trial and error then anything else. It could be alot of things, first off I think you need to thin the paint out more. You might try painting on a less windy day as well.
Feb. 27, 2011 7:15 a.m. DILYSI Dave SuperDork

I now that when we want a textured finish, we turn the pressure down. That makes it come out in globs.

I'm not sure where the 40 = 6 conversion came from, but 6psi @ the tip sounds way low.
Feb. 27, 2011 8:04 a.m. Dr. Hess SuperDork

What HF gun are you using? One like digdug18 hotlinked? That one should be just fine. I've shot a bunch with the next cheaper (~$10 on sale) HF HVLP and that's my favorite paint gun now. When you say "at the tip" do you mean you crank it down to 6 at that on-gun regulator? I'd say try about 30-40 PSI there and see how you do. You might want to try shooting some Rustoleum on a spare panel and play with all the settings so you don't have to shoot your expensive finish paint. Thin the Rustoleum about 20-30% with generic "paint thinner, made with mineral spirits" and not the low odor kind.
Feb. 27, 2011 8:10 a.m. former520 New Reader

I am using the exact gun as shown above. I am at 40-42 psi at the on gun regulator. I will try and crank it up a little more as well as thin a little more. I am using the same brand thinner as the paint I am using. THe thought is if it is all the same brand it "should" work well.

I was looking for the next gun down, but could not find it. They only had the one with the regulator on the gun and the smaller detail gun at my local HF. I had read that the regulator one reviewed pretty fairly as well.
Feb. 27, 2011 8:16 a.m. Raze Dork

why not just use some roll-on truck bed liner on the bed of your truck?
Feb. 27, 2011 9:22 a.m. former520 New Reader

Raze wrote:

why not just use some roll-on truck bed liner on the bed of your truck?

Right now it looks like a glossy bed liner on the bed sides. Oddly enough, the inside of the bed seems to have less peel, that paint was shot on the natural, unprepared surface as well!
Feb. 27, 2011 9:47 a.m. motomoron HalfDork

Firstly -

Here's a piece I guest-wrote for Roadracing World on painting race bodywork. It covers the basics of using acrylic urethane.

Paint Article

Second - paint, mixed and ready to shoot should be thicker than milk and thinner than cream. Maybe ATF if that's your frame of reference.

The use of proper mix cups w/ the various scales on the sides is very helpful. Better is a mix stick.

Orange peel is generally caused by paint not atomizing properly or "laying out" - thinner paint, more air pressure, adjust the fan, make sure the nozzle orifices and cup lid vent hole are clear.

Thirdly - Don't shoot a drop on the actual thing you're painting 'til you verify the gun settings, pressure and viscosity on a test panel. I have a bunch of old rectangles of sheet metal. When I'm priming I shoot a couple. When I'm ready to paint I make sure it's all good on one of them before committing to the vehicle part.

Lastly - Nice things are nice. I painted with a $200 DeVilbiss Finish Line HVLP gun for years before buying 2 Sata Jet non-HVLP guns from a shop that had to become HVLP compliant. The Satas are amazing - I got the pair for a couple hundred, but new they're over $500/ea.

BTW - on the Finish Line, despite it being HVLP, I never got it to really lay down beautiful paint with less than about 25# at the cap. The Satas run more like 40#.

Paint guns are like helmets - by a cheap one if you've got a cheap head.
Feb. 27, 2011 11:19 a.m. Keith SuperDork

I've used those HF guns. They're pretty good, and you can lay down a pretty good finish with them. I really like the detail gun in particular. They do like to be run a bit high on the pressure. From what I recall, orange peel is almost always related to pressure.

However, they are HF products. I'd disassemble the gun and see if I could see anything wrong with the manufacture. HF stuff isn't always consistent in quality.

I just splurged on an Iwata and there's simply no comparison - wow. It runs freakishly low pressure too.
Feb. 27, 2011 11:46 a.m. WilberM3 HalfDork

pseudosport used a cheapie LVLP gun after his HVLP cheapie died and he said he preferred the LV as he found it to lay down smoother and needed less wet sanding afterwards. i cant speak to settings used, paint, or any other probably important variables, but that's how i heard it from him.
Feb. 27, 2011 4:11 p.m. Kramer HalfDork

Are you sure you don't have water in your system? That would make the paint come out in globs. You have to drain the tank often when painting, and you should be using a water trap, too.
Feb. 27, 2011 5:13 p.m. former520 New Reader

I went our and played with a couple more cups of paint. I ran out of things to shoot to test, but I did get it much better.

I cranked up the pressure from 40 to 60 and started to get what looked like sand almost under the paint. Like I was painting on sandpaper. The paint would lay, but was odd, backed it down to 50 and it was much better. Also played with the paint volume knob and backed down the amount of paint. Seem to be good, no painting on the truck, seems too cool today at 52-54F and a lot of wind.

I do have one of the in line filters on the line. I have noticed with my tank that it spits water on occasion when I am using the blow off gun. It is an 30ish gal Craftsman upright with a 5hp oil-less compressor. Haven't had any issues with not having enough air.
Feb. 27, 2011 5:48 p.m. 44Dwarf Dork

Check the knurled nut on the actuation rod. Air leak there can cause all sorts of problems.
Feb. 27, 2011 6:07 p.m. triumph5 Dork

Could the paint have been coagulating before it hit the metal due to the chilly temps coupled with a trace of water in the air line? I've sprayed gel coat, but not straight paint, and that stuff is extremely temp sensitive. So?
Feb. 27, 2011 7:32 p.m. jhaas Reader

i agree the HF will give an acceptable finish. single stage is tougher to spray because its so thick. turn your pressure up 40lb on the HF regulater, fan wide open, needle full open, then thin the paint untill you get results. but i like to paint fast and heavy...
Feb. 28, 2011 9:37 a.m. dansxr2 Reader

Also the pressure being turned up could be "Drying out" the paint before its hitting the surface giving an roughed surface.
http://www.harborfreight.com/media/catalog/product/cache/1/image/9df78eab33525d08d... I had these paint guns and they worked VERY well for the price! I really liked the way the sprayed. I even did repairwork on my former father in laws girlfriends car and that a Pearl White Kia and the blend/transition around the damaged area was great.

If you can post a pic, maybe we can get a lil more insight of whats goin on.
Feb. 28, 2011 9:45 a.m. pinchvalve SuperDork

Flat satin black became a hot look, why can't orange peel become the next hot look? It would make DY painting so much easier.
Feb. 28, 2011 3:18 p.m. kpm Reader

Screw the fluid knob all the way in, then back it out 3 and a half turns. Your air control on the side of the gun should open full. The little knob on the bottom of the handle should be all the way in.

Now hook up your air, and while the gun is empty pull the trigger in completely and set the air pressure at the regulator on the gun (around 40-45 psi). You should have a 1.4/1.5 needle/nozzle combo for single stage.

Then practice, practice, practice.

Oh and you should have a 8 to 10 inch fan pattern when you test it on a scrap panel.
March 1, 2011 10:53 a.m. dansxr2 Reader

Keith wrote:

"I've used those HF guns. They're pretty good, and you can lay down a pretty good finish with them. I really like the detail gun in particular. They do like to be run a bit high on the pressure. From what I recall, orange peel is almost always related to pressure."

You seem to share my thoughts too... I left my HF guns in FL when I left my wife, as well as everything else I owned.. Once settled back in WV I splurged and bought one of the Eastwood Concourse guns, and was very suprized with it. Its well balanced and has LOTS of fine adjustment. The aluminium cup is also teflon lined for easy cleanup. I got it on sale for $200 with both a 1.4 and a 1.2 tip as I have a cheap Siphon Feed Primer gun.

Still sounds to me like the air pressure is up too high, and the fluid is possibly too low. I'm far from a professional, just tryin to help a fellow GRM'er :)
March 1, 2011 11:34 a.m. motomoron HalfDork

Below 60 F is cold for painting. When I was using acrylic/urethane products like PPG Delstar I'd have a deadline to get a bunch of sets of race motorcycle bodywork done in early spring and sometimes I'd have to resort to the fastest reducer possible and being super careful to avoid runs.

75F and low RH is perfect - but it's an imperfect world.

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