Monday, September 6, 2010

Spraying 2k Filler Primer

A few days have passed now since I sprayed on the etch primer. I would have liked to have done it within 24 hours, per the product data sheet, but I ended up having to help my friend move out of his garage. Luckily, he's letting me keep my space here for another month, and I'll have loads of time to work more leisurely.

Because of the wait, it is recommended that I scuff the etch primer before I spray on the 2k filler primer.
I used a maroon scotchbrite to scuff the entire surface of the etch primer, and then went over the whole car twice with Wax and Grease remover to clean off all the dust I created and get the car ready for primer. 
I also spent some time cleaning up my workspace to make walking around the car a little easier, and spent some time re-assembling the spray gun for spraying today. I also decided that mixing the etch primer on the floor was a pain, and found some good counter-space to keep and mix paint on. All this prep took about 1.5 hours. Here is my new workspace. You can see the paper on the wall for testing spray patterns:

For spraying today, I will be using more Sherwin Williams automotive paint products. I will be spraying on the "ACME Finish 1" brand 2K HS Urethane Primer (Product# FP410, 1 gallon, $75). It is mixed 4 parts, with 1 part of 2K HS Hardener (FH411, 1 Quart, $35). There's a good desciption of 1K primer vs. 2k primers vs. epoxy primers here.

This "filler primer", as I will be referring to it, is a high-build, high-solids primer. You could almost think of it as spray-on bondo. You put a few thick coats of it on the car, and then use sanding blocks to take off all the minor ridges and bumps from the primer, leaving perfectly flat panels which look fantastic once painted. Any previous sanding scratches or minor dips or dings can be leveled with this stuff. It also removes orange-peel (ie, highly textured paint) and serves as a good base to spray the paint over. A good application of filler primer coupled with careful block sanding is something that separates a fantastic show-quality paint job from a lousy job. Here you can see a car that could have used some better filler primer and block sanding to even out these panels:
I used the same system for painting the car as outlined in the etch-primer section. I knew that any drips or sags would sand right out during block-sanding anyway, so I sprayed it on pretty thick. Once it had the prescribed time to flash-dry (using a kitchen timer), I gave it some extra time, and then sprayed on a second thick coat. Because there are so many solids in the primer, you might need to use a bigger nozzle on your paint gun. I used a 1.8, which worked well for me. The material is so thick that it has a definite texture to it as it cures on the car. Here you can see the distinct orange-peel texture on the front fender after two coats. (see the full size picture):

After going over the whole car twice, I went back and sprayed over many of the edges and ridges that I was worried I might sand through (like the two horizontal body lines on the side of the car, and the two lines down the middle of the hood.), and a few spots that I had noticed earlier had a dent or ding that hadn't gotten filler earlier. Here you can see the results. Again, I didn't spray in a booth since I figured most of the primer is going to get sanded off and end up on the floor anyway. If you have already prepped your bumpers and other parts (sunroof, gas cap, spoiler, etc.), don't forget to spray them now too.

For reference, I only sprayed the main body of the car today, and none of the parts which I still have to prep. I used about 3/4 of the primer I bought. I don't think I'll have enough (primer, money, time or will) to do a second spray and block-sand after the first blocking is done. This is a daily driver, not a show car.

I have read in a few books and heard in general that the primer could be sanded soon after curing, but that you get the best results if it is allowed to sit for a week before block sanding. This allows for complete curing and any shrinkage that might occur. I am in no rush now and will work on some other stuff while the primer cures. Spraying the primer and clean-up afterward only took about 1.5 hours. Here is the garage now that all my friends stuff is out and the garage is all mine:


Time spent today: 3 hours
Money spent today: $110