Need Tips of Block Sanding with SPI Primers

P

Piston Speed

Howdy all,

I have a '72 Dodge Demon project car which is currently in SPI black epoxy primer after being sandblasting with both crushed glass and coal slag.

I've been reading up a lot on block sanding on various message boards and magazine articles, but since everyone seems to have their own way of doing it that works for them, I'm a little confused as to how I should proceed personally.

I have some dents I need to fix which may necessitate body filler, such as in the quarter panels, but the whole panels won't need filler.

So once I finish the filler work with 180 grit, should I then block sand the rest of the primered panel with 180 grit as well? Then shoot the entire panel with primer for build?

I'm thinking about using SPI grey epoxy instead of 2K since I've read some benefits of epoxy for blocking on here and the grey on top of black will act as a guide coat. Should I go with the epoxy over the 2k?

And once I spray the grey, should I block that with 180 as well or just start 320? Will I need to spray another coat of primer of top of that, not including burn throughs?

Also, after 320, will I need to spray more coats before going to 600? I'm painting with metallic so I'm going up to 600.

I read on another forum not to more than double grit sizes, so I'm going from 180 - 320 - 600 after filler work.

Thanks!
 
Black epoxy doesn't need a guide coat either. It turns a shade different as you sand it.

You sand because you need it. Not because theres a rule of thumb telling you to.

Yes, I'd 180 the entire panel once you finish out your filler. Lets you know where you stand with remainder of the panel. I'd then put 3 coats of epoxy with a 1.5 tip if I was doing all epoxy or I'd do 1-2 light coats of epoxy followed by 2k the next day.

I'd block that quarter with 120 grit and build with primer until it right. Might take 1,2 or 3 times to get it flat. Coarser grits cut flatter than 180 for me. When I'm happy with the results then reblock the quarter with 180 to smooth out the coarser 120 scratches. Spray 2 coats primer followed by a round of 240 grit with 1 coat of primer and then 400 and paint. It all depends on the job though and grits and procedures are adjusted based on project.

Just remember your not blocking for fun, your reading the scratches and patterns and they don't lie. If you see them in the pattern they will be in the final product.
 
I appreciate the response; sorry for the late reply.

What if I decide to use 2k in lieu of more epoxy? I'm assuming if I go with 2k instead of epoxy, I'd shoot three coats of 2k after 180.

When you say "build it with primer," do you mean shooting burn-thrus with primer while blocking?
 
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