sanding key

Sanding key = sanding block ??

I recently "discovered" these Durablocks, they're expensive but the best you can use for blocksanding IMO.... cheap rattlecan black for a guide coat works great.

I am working on an old VW right now, I'd say I sprayed about 3 layers primer after metalworking and Bondo.... most of the primer gets sanded off anyways.... tint the different layers so you can see when you sanded thru to the previous layer.

I spryed two coats black epoxy primer first (over the filler and exposed metal) - then two coats primer, sanding, more primer, sanding.... I still have high spots where I keep sanding to the black epoxy....
 
or 'guide coat'

guide coats are very important. Once you're done block sanding the primer with guide coat with f.e. 320 wet you'll see all the low areas that are still showing the guide coat color.

You can use rattlecan paint for a guidecoat, that's the cheapest and most convinient. Over reduced base is better but you'll have to fill the compressor and clean your gun - too much work IMO.... unless you have compressor up and running anyway and the gun is waiting for the next load of primer.... depends on the situation I guess.
 
How many of you guys used sanding key to sand the primers and how many layers of primer did you paint and sand ?

This is what I prefer to use the most. It cost a little more but is very easy
to use and you can apply it as light or dark as you wish, also if any is left
behind on the surface it will not harm any top coats.

3M5861.jpg

Layers of primer depend on quality of body work. In a professional shop our
body work is expected to be good enough that the prep shop does not have to
apply anymore than 2 coats of primer.........light block sand to remove light
sand scratches and orange peal from the primer.......then paint.
It is not for straightening panels....they should be "straight" before the primer
is applied.

To often people will use primer as body filler. Years ago the practice was
3 heavy coats of primer....Block sand.......3 more coats.....Block.....light coat
of primer ..... Paint. That's a lot of wasted primer ( and Money ) for improperly
finished Filler work.

The idea is to finish body work to P180.....then prime just enough to prep for paint.
Using the guide coat on primer sand just enough to remove any orange peal
and "very light" imperfections then top coat.


As A Note: The same holds true with Paint (base coat)....you only need enough to achieve
color build (or coverage), that's it, if 2qts does it there is no need to spray
a gallon of paint on the car........just wasting materials.
 
Well I used the filler and worked it out pretty good. Panels looked very straight but when sanding with finer and finer paper I kept on finding low areas in the primer. Right now I have 3 coats on there. Maybe I'm taking it a bit to far. Don't know.
 
Filler Work is not something that is easy to perfect.
So don't beat yourself up over it.......if this is your first time.

Except for one corner on our '81 the body is in original condition.........
It "Looks" very straight but run your hands over it a few times and you'll
soon discover the body is as wavy as the ocean.

I use the "guide coat" straight on my body filler.
Since your is already primed....(no big deal)......go ahead and block sand the car.
Repair any low areas and imperfections with a glazing putty, I prefer EVERCOAT Products.
And use the guide coat till everything starts blocking straight........before you
apply any more primer. The glazing putty is far cheaper and quicker than the
primer.

I would not sand with anything finer than P180 till I felt I was ready for that
finish prime before paint.

Unless your painting the car BLACK or other real dark color.........any minor waves
you may end up having in curved areas, like over the fenders probably will
never show up anyhow to the average eye.


Good Luck and Keep us Posted........:thumbs:
 
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