As you can see in the main picture, the car has been painted. Unfortunately, my paint job could have turned out better. Read on to find out what went wrong.
First, I didn’t do a very good job spraying the paint. There was a lot of orange peel in the finish. I couldn’t get the paint to lay down smooth no matter what I did: varying the distance of the gun to the car, moving the gun faster or slower across the panel, varying the air pressure, nothing made a difference. I either got orange peel or runs and sags!
I still haven’t figured out what I did wrong, but I’ll post it when I do. All is OK, though. I anticipated having to sand the car anyway. Our shop isn’t exactly the cleanest, dust-free environment, and I did end up with some dirt in the paint.
My second problem was something I didn’t expect: sand scratches in the primer were visible through the topcoat on the hood and decklid! I thought I had done a good prep job, but obviously, that wasn’t the case. Here’s what happened.
Paint and primer need something to stick to- a rough surface with “tooth” as painters say. It is entirely possible to sand a panel too smooth, and your next layer of paint won’t stick to it very well. Knowing this, I didn’t “spare the rod” when prepping for primer: I used 40 grit on the roof, then sanded the whole car with 80-grit on a DA, following that up with 150- and 220- on sanding boards. It’s cool to do this; the primer should fill 150 grit scratches.
Be warned, though, you must sand more thoroughly with each successive, finer grit. 40- and 80-grit paper is really aggressive and can gouge the paint more deeply than what can be smoothed out with a quick scuff of lighter stuff. In other words, you actually have to sand through more of the paint when using less abrasive paper to even out the scratches you made with the more abrasive paper.
In areas where I didn’t do this, I could still see the instantly identifiable swirly scratch pattern made by the Dual Action sander even through three layers of primer!
To fix this prior to topcoating, I decided to block sand the whole car again. I started blocking with 150-grit before moving on to 220- and finally 320-grit. Paint generally is supposed to hide 220-grit scratches, so I thought I was safe. Guess what? It didn’t.
In hindsight, I think I created the same error as I did prior to priming the car- the 150-grit scratches weren’t sanded out thoroughly enough. Plus, I was dry-sanding the primer, and I had problems with the primer clogging in the sandpaper. Dragging the clogged sandpaper across the panel left behind some grooves, too.
If I were to do this over again, here’s what I’d have done, starting with prepping for primer.
First, the Valspar primer may not be the best filler primer; it is probably best used as a primer-sealer. I would have sanded the factory black-and-white paint the same way I originally did because it was heavily scratched, chipped, and the clear was cracking on the hood and decklid. But I’d have put one coat of Valspar primer on and followed with two coats of a dedicated build-up primer. That probably would have done a better job of filling the DA sand scratches. Then, I would have block sanded the filler primer starting with 220-grit paper, not 150. Depending on what color the build-up primer was (most of them are beige or light grey) I probably would have sprayed another coat of the charcoal-grey Valspar primer over the filler primer to give my so my glossy black topcoat a dark base to go over.
There is some debate among painters about wet sanding primer. Some primers are porous and will absorb moisture that will eventually come back out, usually after you’ve painted the car. But epoxy primers, like the Valspar primer I used, are generally weatherproof. I probably should have wet sanded it with 400-grit wet-or-dry paper. Lots of lessons learned with this paint job!
More details of the paint I used in the next post.