Block sanding, checking panels for imperfections....

[DoubleNickle]

Using SPI epoxy, no primer....

I'm on my third block sand and panels are looking pretty darn good for a first timer (pats self on back lol). My question is, what's the best way to check my work for imperfections or waves, etc.. ? The epoxy is pretty shinny before sanding but imo not shinny enough. After block sanding I wet the panels with wax and grease remover which works but it dries too fast and is expensive. Also tried water which also works but was wondering if there is a better technique or product I could use.

Thanks for the help!

[Rick_L]

What you need to do is use what's called "guide coat".

3M has a product called guide coat. It is a black powder. You spread it over the panel with a paper towel or rag, then block sand it off. As you sand, the high spots will sand through the guide coat immediately. Hopefully you are past that stage. As you continue to sand, the guide coat will remain in the low spots. This will tell you how straight the panel is and what you need to fill or otherwise repair.

There is an alternative to the 3M product. Dust a very thin coat of lacquer type primer surfacer over the area. Or you can use rattle can sandable primer surfacer.

I like the 3M stuff as it will clean up with wax and grease remover. The lacquer primer surfacer really does need to be removed, and you must sand that off, as you don't want that stuff sandwiched between your primer/paint coats.

How do you find the SPI epoxy as far as build and sanding? I know some guys love it but I just can't bring myself to block sanding epoxy, preferring to use a urethane primer surfacer because of its sandability. Have you ever tried a urethane primer surfacer like PPG K36?

The reason I ask is that some SPI users seem to get all huffy when this question is asked and when someone gets huffy in reply I get wary about whether to believe the answer.

[LEE T]

You should make sure you are not building too much material on your car. I don't like to use the rattle can guide coat, because it has to be all removed, and I don't want to sand the areas that are already too low. What works good for me is using a lighter or darker shade of what ever I'm using for blocking, and use the longest board that will work for what you are sanding.

Rick, the SPI epoxy works good as a blocking primer if the panels are already pretty straight. You have to give it at least 24 hours to dry before trying to sand. I start sanding with 120 grit and that sands pretty good. I just do two coat sessions with a 1.3 tip, but some of the guys use 1.4 and put on 3 coats at a time waiting a couple of hours between coats. SPI uses a lot of high end ingredients in their products to get them to perform better for the restoration market. Clears are designed to cure very good without baking, and clears can be built up more than you are use to.

Its something that you just have to try yourself, because the guys that use it, like it so much that its hard to believe their enthusiasm. But it almost always makes a believe out of everyone that actually tries it.

[chevynut]

I did all my rough blocking with Evercoat SlickSand, a polyester primer. I sprayed PPG DPLF on first, then the SlickSand. The nice thing about the SlickSand is you can tell where the low spots are without a guide coat. If I had a low spot, I spayed that first, let it flash, then sprayed a larger area to build up the low spot faster. I tried to be really careful not to sand through the epoxy, and not to leave too much SlickSand on either.

I put one coat of PPG K36 over the SlickSand and it's now ready for final blocking. I don't know if I'll need the guide coat or not, but I have some rattle can stuff in case I do.

[Hotroddder]

Once the smaller low spots are removed, wipe down the panel and spray a light wet coat of wax and grease remover over the whole panel. Quickly while it is all wet get at a low angle and you will see any slight wages or any issues in the body. Just like having a wet top coat for a few seconds.

I was surprised what I had missed the first time I tried this. I thought I had the quarter straight, but it revealed several things I did not like.

Dick Olsen

[chevynut]

Another trick I learned years ago is turn off the lights, and shine a flashlight down the panel with the light as close as you can get to the panel. It shows up all kinds of stuff and you can look as long as you want to. I tried the oil and wax remover and I couldn't get it to work very good for me...maybe it's the dry air here.

[DoubleNickle]

Thanks for the help!

The technique I found works the best for me is plain old water wiped on heavy with a rag or by using a spray bottle. It works and is a lot cheaper then w&g remover which did not really work for me because it would dry so fast in this 85 degree weather I have here in south fla.