Paint finishes

August 27, 2006, 09:26:58 PM

Long but need help on solvents and paint problems.

Okay, last weekend and the first half of the week we finished prepping and painting my car. There's a few problems we ran into and could use some answers if anyone knows.

First off, it was all setup for hvlp. Have a couple hvlp guns with different tips and a decent sized compressor (18psi@40psi) with a large tank. We went with epoxy primer/sealer, filling primer (don't remember which type), more sealer, basecoat, and clearcoat. We never ran out of air, but the basecoat finish had really aggressive orange peel after spraying it on. Temperature was about 73-75 degrees with 50psi at the gun, compressor cycling on and off every minute or couple minutes, using Dupont Urethane/75 degree activator. As far as I know, it should have flattened out a lot more, especially with the correct mix ratios ( I think its 1:1 on the basecoat, don't remember off the top of my head). Anyone know of a reason behind this?

Second, the hood and trunk each had a spot raised up slightly higher from primer that we could not see with just the sealer and/or water sitting on top and the size of sanding blocks were too small to flatten out. Since the paint needed to be redone but the car had to be driven soon, we decided to just redo the hood and trunk. After sanding them down and re-priming, we plugged in the non-hvlp we had to give it a try. Forgetting we had a gallon of some cleaner that the paint shop recommended, we used it to get all the dirt and dust off. After 5 minutes, the paint went on perfectly smooth/flat but a few seconds later, the entire trunklid began to bubble up, I'm assuming from the cleanser having not fully evaporated. We quickly removed all the paint we had just put on. After hours, we resanded, reprepped, and washed the trunklid and sanded the hood some more. This time NOT using the cleanser, but some water and a sponge instead. The first coat of paint went on smooth again. Did both the trunklid and hood at this point and no signs of bubbling.The second coat went on 20 minutes later and again, it went on smooth. Coming back to the paint 15 minutes later, there was a 3 foot long tree branch shaped lifting of the paint on one side of the hood. Where the hell did this come from? It wasn't on the first painting of the car.

A drop of that cleanser got on the bumper cover and started making the 36 hour old paint bubble up. It is not degreaser, thinner, or anything of the like. I'm not sure what it is, but it seems to be harmful so we're not using it anymore. It is now 3 days later and I tried deep sanding/prepping/repainting the spot of the hood with the prior lifted paint. It did it again.

What the hell is this and how will it go away?

Also, why is the hvlp giving me all this orange peel in ideal conditions, but the other type is giving me a near perfect finish (with a lot more overspray though)? I can't think of anything else that would affect it this badly. Had a good hose, water traps(one at compressor, one at gun), everything.

The plan is to get to the bottom of this and just do it panel by panel with the non-hvlp. Dealing with the whole car and cost of materials is too much of a pain, especially since I already took the week off to spray the entire car.

Other than the orange peel now and the spot on the hood, the entire car looks perfectly straight with black paint. All the dimples and dents are fixed.

Paint finishes

Reply #1 – August 27, 2006, 10:51:13 PM

I've heard of people using aircraft stripper and something like that happening. I tell you to clean the parts with lacqor thinner or reducer before you paint. That really sucks. I know we sell the dupont at work and the base color is 1:1 mix with the base maker. I don't remember it saying a temp on the label. I think it is fast, med , slow. Also it would also depend on witch paint line from dupont you are using. I really think that cleaner might be the air craft stuff. I've heard of several people not getting it cleaned off good enough and everything comeing off or pealing bad. Could be something else though.

Paint finishes

Reply #2 – August 27, 2006, 11:10:40 PM

What brand of primers did you use? I'm thinking maybe there was an incompatibility problem between the primer and paint.

I learned a trick years ago...instead of lacquer thinner or Prep-Sol...use rubbing alcohol. It evaporates more quickly. Of course this would be after washing everything with soap and water. Rubbing alcohol is also a lot cheaper than Prep-Sol, at least for just one car.

Sounds like everything else was done correctly though. That is an odd problem. I have had that happen a few times. It took stripping, sanding, better (more thorough) cleaning, and respraying, and most of the time I had great luck. Some plastics like polyethylene just naturally seep chemicals straight through the paint and that just screws everything up. But what you did...man, it sounds dead-on correct to me. It just may be a difference in primers vs. the base/clear.

Paint finishes

Reply #3 – August 28, 2006, 12:38:55 AM

Don't remember the brand (don't have it with me right now), but I think it was something urethane. I think it was a 2 part ppg primer. Same with the black epoxy primer. What I find odd about it all is that the original coat went on fine, its after using that cleaning chemical (that the paint store RECOMMENDED for cleaning) that we started having problems. I'll see if I can get the label off the thing.

Right now I'm just sanding the hood down, having it be different colors will look better than having it lifted a quarter of an inch.

edit:
Its just labeled as one of the products "for lifting and removing wax, grease, oil, and other contaminants from surfaces to be painted"