What to use over 2k primer to fill low spots?

K

kortensi

I am working on a 71 Vette. I have 3 coats of Epoxy Primer and 3 coats of 2K Regular Build Primer applied to the car.

I started sanding today and have a few low spots.

Is there a particular product that I can apply over the 2K to raise these low spots?

or do I have to sand the 2k off and apply filler over the epoxy and then primer over the filler?


Thanks
KO
 
People do often apply filler over scratched up urethane surfacer but it's not the best scenario.
 
Have you sanded through your primer and still have low spots?
Generally I spray the epoxy and then lightly block sand with say 150 grit just to dull the surface. Works like a guide coat as the low spots will remain shiny. I do my filler work over the epoxy and then seal with more epoxy before going to the build primer. From there the build primer gets guide coated and block sanded to remove the guide coat. Any small imperfections will usually come out and if not shoot some more 2k primer and repeat the guide coat block sanding.
 
This scenario is partly why we and a lot of other resto type people use epoxy at least through the initial stages of blocking. Low spots can be filled on top of epoxy with complete confidence. Filling on top of 2K is done like Bob says, but it's possible for the primer to lift or absorb stuff from the filler and then shrink later. When we mess up and have to skim 2k, we cure the area REALLY well with an IR lamp before and after filler application to make sure all the solvents are kicked out from below the filler before re-priming.
 
If you use a polyester highbuild on your fiberglass, you minimize those problems...I believe I the all epoxy, or epoxy and polyester highbuild only....Dave
 
I figured I'd post some pics to show what I'm dealing with.

I have sanded to 220 over almost all of the car.

Here is an overall shot with two low points.

DSC04178.jpg


and a close up

DSC04179.jpg


DSC04180.jpg


and the rest are more of a tiny scratch/nick in the underlying fiberglass.

DSC04181.jpg


DSC04182.jpg


DSC04183.jpg


DSC04184.jpg



I have some rage extreme that I was thinking I would mix up and use a razor blade for filling these, then give it overnight to cure before sanding and then reapplying just those spots with 2K.

- - - Updated - - -

I figured I'd post some pics to show what I'm dealing with.

I have sanded to 220 over almost all of the car.

Here is an overall shot with two low points.

DSC04178.jpg


and a close up

DSC04179.jpg


DSC04180.jpg


and the rest are more of a tiny scratch/nick in the underlying fiberglass.

DSC04181.jpg


DSC04182.jpg


DSC04183.jpg


DSC04184.jpg



I have some rage extreme that I was thinking I would mix up and use a razor blade for filling these, then give it overnight to cure before sanding and then reapplying just those spots with 2K.
 
Rage Extreme is more of a general purpose body filler. If you have a finer poly putty it would work out better for you.
 
crashtech;34786 said:
Rage Extreme is more of a general purpose body filler. If you have a finer poly putty it would work out better for you.
Click to expand...

Is there a particular brand name you would recommend?

Thanks
KO

- - - Updated - - -

crashtech;34786 said:
Rage Extreme is more of a general purpose body filler. If you have a finer poly putty it would work out better for you.
Click to expand...

Is there a particular brand name you would recommend?

Thanks
KO
 
Marson Platinum Plus (now 3M Platinum Plus) also specifically states in the tech sheet that existing urethane primer is a suitable substrate. However it is not a glaze. It would be like an analogue to Rage.
 
I have never had a problem using spot putty over urethane primer.
It's done all the time.
I do like to scuff the primer first.
 
Lizer;34800 said:
Marson Platinum Plus (now 3M Platinum Plus) also specifically states in the tech sheet that existing urethane primer is a suitable substrate. However it is not a glaze. It would be like an analogue to Rage.
Click to expand...
I've seen that claim in promotional materials, but not the actual TDS, in which they seem careful not to mention use over any substrate that might have any degree of reversibility the way a partially cured urethane can. In fact, the general "cover our asses" language is found in the Platinum Plus TDS linked above:

When repairing galvanized steel, e-coat, primed/painted surfaces or aluminum, sand with grade P80 3Mâ„¢ abrasive to remove the
paint/primer. Blow off with clean dry compressed air and re-clean the surface using a clean paper or cloth towel and a wax & grease remover/surface cleaner
Click to expand...

Of course, those of us who have already made lots of mistakes, err, I mean had lots of experience with this sort of thing just kind of know when a substrate will be OK to fill on just by seeing how the first spot reacts and sands. If the substrate is too reversible, the coating will peel back and take the filler with it, especially if gotten on too quick with sandpaper.
 
Yes....I've put lots of the Platinum Plus filler over SPI 2k. That was one of the reasons I went with it...because it was stated it could work on said substrate. I never experienced any problem, it's been a few years now.
 
can you spray polyester primer over spi 2k primer to fill some low spots?
 
can you spray polyester primer over spi 2k primer to fill some low spots?
 
57oval;35355 said:
can you spray polyester primer over spi 2k primer to fill some low spots?
Click to expand...

It would be best to stick with the 2k and not introduce another product at this stage... IMHO so just fill the low spots and reprime with the 2k

- - - Updated - - -

57oval;35355 said:
can you spray polyester primer over spi 2k primer to fill some low spots?
Click to expand...

It would be best to stick with the 2k and not introduce another product at this stage... IMHO so just fill the low spots and reprime with the 2k
 
im sure youre right but the problem is, its a really big curved panel (the roof of my bug) and its a little wavy in a few spots. when I try to block it to find the low spots, it all sands the same with no low spots showing up. I know they are there because I can feel its uneven with my hand. I fixed what I could with filler but I don't know how to get it all flat. that's why I was thinking maybe slick sand or featherfill just on the roof? any suggestions on what I can use for blocking the curve? I was using a sponge.
 
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