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Learned by do'n twice
 
Join Date: Jul 2007
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What the Hell Am I doing Wrong

I'm not a painter but I've painted several cars and many panels with good to great results. However, I recently bought a set of HVLP gravity feed guns and started primering my latest project with SL-2K with poor results. I followed the mix instructions (4:1 paint to activator) and am painting at the recommended 10 PSI. New primer gun has a 1.8 tip. Ambient temp around 58 degrees.

The paint is laying on quite rough, seems to be too dry, and with quite a bit of overspray and "sandpaper" texture. I tried adjusting the fan, paint volume, and pressure but nothing really seems to help. I added a bit of reducer, per the the product instructions and that helped, but not really enough,

I need to find out my problem before applying topcoat, a single stage arcylic enamel.

Any advice would be appreciated.

jmd_forest
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Old 03-28-2008, 01:48 PM
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Try mixing it 4;1;1 primer, hardener, reducer
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Old 03-28-2008, 03:37 PM
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Quote:
Originally Posted by jmd_forest View Post
I'm not a painter but I've painted several cars and many panels with good to great results. However, I recently bought a set of HVLP gravity feed guns and started primering my latest project with SL-2K with poor results. I followed the mix instructions (4:1 paint to activator) and am painting at the recommended 10 PSI. New primer gun has a 1.8 tip. Ambient temp around 58 degrees.

The paint is laying on quite rough, seems to be too dry, and with quite a bit of overspray and "sandpaper" texture. I tried adjusting the fan, paint volume, and pressure but nothing really seems to help. I added a bit of reducer, per the the product instructions and that helped, but not really enough,

I need to find out my problem before applying topcoat, a single stage arcylic enamel.

Any advice would be appreciated.

jmd_forest
As Axiom stated, you might try using some more reducer in the primer and just lay on an extra coat. Also bear in mind, coatings flow out much better between 75-85 degrees. If you have the ability to heat the work space, that will help alot on smoothing the texture as you spray.
Old 03-28-2008, 07:05 PM
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Hold the gun closer, 10-12".
Old 03-28-2008, 09:30 PM
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Your pressure should be 10psi at the cap which really means 25-35psi at the gun. I had similar problems. Basically you should be setting your gun pressure so you get a nice fan 8-12 inches from the gun.
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Old 03-30-2008, 10:22 AM
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Thanks for the replies. I was painting at about 8-10 inches and still getting the "sandpaper" texture. I guess I'll wait for a week or 2 for the weather to warm up before trying again while adding the 1 part reducer (I already have the fast reducer, rated 60-70 degrees). I wet sanded out some of the primer today and had a hell of a time getting it smooth, it was "micro-pitted" all over the place after sanding.

I hope outlaw912 can explain the pressure issue further. I have a regulator right at the intake to the gun. The standing pressure was about 25 psi which translated into about 10 psi (per paint can instructions) when the trigger was pulled.

Thanks again for the help. any further tips would be appreciated.

jmd_forest
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Old 03-30-2008, 04:44 PM
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almost all urethane 2k primers must be reduced before spraying. sounds like your problem is not enough reducer.
Old 03-30-2008, 05:43 PM
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I should preface this by saying that I'm not an expert, but here is what worked for me. I was having the same problems as you with polyester primer. The primer p-sheet says 10 psi at the cap, which doesn't necessarily mean 10 psi at the pressure regulator. I assume there is some pressure lost inside the gun. I set my pressure higher at the regulator, 20-25 psi with the trigger wide open. I think it's more feel than anything else.

Maybe someone with more experience can clear this up, but anyway thats what worked for me.

Hope that helps.

Erik
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Old 03-30-2008, 07:57 PM
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Boy, that all goes against what is the norm... cold temps mean 'wet' paint film, the solvent doesn't flash fast enough. Low air pressure and thick paint usually gives you a very orange peeled finish not a sandy one. With the three conditions you are discribing I'd have thought the paint would be running off.
Are you positive you mixed the proper ingredients? Sounds also like it could be seedy paint. A quick test is to take some paint and pour a little onto like a piece of flat smooth metal. Take a squeegy or something and smooth it out If you can see 'bumps' it may be kicked out. We use grind gages for this to check the grind of pigment.
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Old 03-31-2008, 05:19 PM
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Finish was a horrifying combination of orange peel and sandpaper, in different spots. The ingredients mixed: Transtar 2K Kwik Prime and Transtar 2K Kwik Prime Activator. A review of instructions does allow for "up to" 1 part reducer. I originally didn't use reducer since the instructions on the previous Starlite SL-2K primer and SL-2K activator I was using noted to use reducer only if being used as a sealer (That primer job sucked too but I was attributing this new suck job more to the new gun and my inexperience with it). Things improved a little when I mixed in some Urethane Fast reducer, but by then most of the damage was done.

So... I've wet sanded it out with 220 and finished up with 600 grit but still have many pinpoint sized micro pits. Can I reshoot a few good coats and sand out or should I continue sanding MORE before shooting.

Thanks for the help. I seem to need it.

jmd_forest
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Old 04-01-2008, 06:23 AM
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I've seen that before with those kinds of primers, if you really want to save yourself a lot of grief, I suggest sanding it with 150 grit and start all over, those pinholes never go away.

Good luck
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Old 04-01-2008, 06:55 AM
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I will take that advice and sand out all pinholes before reshooting. I'll also reduce the primer and wait for warmer (65-70 degrees) and dryer weather. It's around 70 today but raining. I've always heard humidity and auto paint don't mix.

jmd_forest
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Old 04-01-2008, 07:11 AM
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So... sanded out and reshot the primer but it still didn't come out as smooth as it should so I wet sanded again to a perfectly flat surface. Started applying the finish coat, single stage acrylic enamel, using the new gravity fed HVLP with 1.4 tip gun. I followed the mixing instructions exactly (8 paint: 2 reducer: 1 hardener) and did some research on the gun setup resulting in upping the inlet pressure to 40 PSI and painted on a 70 and 65 degree day. I'm getting much better results but there is still some orange peel. I seemed to alternate between applying the paint too dry or too heavy and running the paint. However, after wet sanding out the initial finish coats and reshooting, the finish is pretty good (some minor orange peel in a few spots) or at least "good enough" for my son's first project car ($500 86 944 + $1000 parts).

Since all of the finish coat so far is on panels removed from the car (hood, sunroof, bumpers) I'm hoping I can get some advise on improving my results on the main car body. Again, I think I'm putting the paint on too dry but It seems to run when put on wet. (Note: I'm using "fast reducer 60 - 70 degrees)

Any help would be appreciated.

jmd_forest
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Last edited by jmd_forest; 04-14-2008 at 06:46 AM..
Old 04-14-2008, 06:43 AM
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Quote:
Originally Posted by jmd_forest View Post
Any help would be appreciated.
Can you show us a few pictures? Don't feel too bad either, HVLP's are very hard to work with unless you're a pro like Axiom.

If it's orange peel you can reduce the paint further but still using the same air pressure. That should get it to lay down better. If it's dry spray you'd want to lower the air pressure and thicken up the paint. In any event hold the gun about 8 - 12" from the substrate staying perpendicular to the work. End your strokes off the panels then come back overlapping 50%.
I'm not familiar with the brand you are using. Maybe the paint also just sucks?
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Old 04-14-2008, 11:45 AM
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I'll give your suggestions a try. How much do you suggest I further reduce the paint? I'm concerned with over
thinning since my initial work on the valence resulted in many runs. I've watched a few YouTube auto painting videos and these guys fly with the gun. I'm moving at maybe 1/2 their speed or I can't maintain a wet edge. I do keep the gun about 10" or so from the surface and try and always maintain a perpendicular angle to the surface by following the contours of the body and never arcing the gun. I do always start and end the spray into the air before and after the edge of the panel.

I'm using Restoration Shop Acrylic Enamel from TCPGlobal. Acrylic Enamel because the PO noted he had a MAACO paint job done and I didn't want to risk lifting the paint by using incompatible paint (been there, done that before). The Restoration Shop brand because it's cheap and this is (supposed to be) a cheap project.
Some pictures are below:
This is the hood. Very tough to see any orange peel

This is a better closeup. If you look just below the reflection of the garage windows you can see some orange peel.

Some of the other panels after wet sanding and reshooting the original finish coat on the valence.


Any help would be appreciated I'm damn tired of wet sanding the initial finish coats. I've actually sanded off my fingerprints.

jmd_forest
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Last edited by jmd_forest; 04-14-2008 at 04:14 PM..
Old 04-14-2008, 03:56 PM
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Forgot to put in previous post: Would it help to wait for warmer weather (75-80) and use medium temp reducer?

jmd_forest
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Old 04-14-2008, 04:13 PM
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It's tough to see the OP but certainly can see some type of defect. Is it just not wetting out? Almost looks like it. And that hood being a horizontal surface should just about look like glass. With the right reducer I wouldn't worry about the temp. as long as it's within reason. Try another 5% reduction.
I'm sure you have thought of this and have done it but was the surface good and clean? Did you tack cloth it? If so did you VERY lightly run the cloth along the surface? They can sometimes leave a residue that will effect the surface tension of the substrate and cause finish problems.
Good luck and please post results and or any more questions you might have.
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Old 04-14-2008, 04:31 PM
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Thank you for your responses. I wish I could attribute the problem to surface contamination. The surface was wet sanded the previous day using a bit of dish detergent. Immediately prior to painting I lightly wiped it with reducer followed by light tack cloth. The finish of the hood prior to finish coat was absolutely smooth. (320 followed by 600 grit wet sand). I was concerned at first about wiping with reducer but I had the same problem on the sunroof and that was simply tacked off before shooting.

Sorry to sound stupid, but what is "wetting out"

jmd_forest
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Old 04-14-2008, 04:57 PM
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Wetting out...hmmm... Uhhh...Think of a freshly waxed car vs. a car that hasn't been waxed in years. The water on the car that hasn't been waxed flows over the surface, it wets out. The water on the freshly waxed car beads up, it doesn't wet out the surface. You want that when waxing but not with your paint. (And there are no stupid questions, maybe some stupid people asking questions ).
With the surface prep you've done it sounds like it's either technique, paint or a combination there of. But what does sound strange is the different surface quality, (OP & dry spray), on the same parts. That's what makes me think something is still weird with the surface.
This may sound stupid but work on your technique until you get one or the other. Then you can adjust the paint and or air pressure/fluid flow accordingly.
Wish I was a bit closer I'd certainly come down to have a look. See if possibly you could get better pictures of the OP & dry spray.
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Old 04-14-2008, 05:22 PM
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Ok guys, this is what I gather so far, any paint nowadays is reduced 4 to 1 to 1, with the exception of CLV, your paint is being reduced 8 to 2 to 1, economic paints do that, because their pigments are weak and won't achieve hidding with the normal reduction ratio. try a 4 to 1 to 1, but I also thought about this: is the fluid needle on your gun all the way open, a 1.4 is a minimun for some medium solids, make sure it's all the way open. Don't get discouraged, if this was easy, everybody would be doing it.

Thank you for your contribuitions Mark.
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Old 04-14-2008, 07:17 PM
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