primer sanding

[GoMangoBoys]

We are getting VERY close to firing up the paint gun full of Plum Crazy.   We will be spraying Nason basecoat clearcoat in plum crazy.  We have a coat of etch primer, followed by 2 coats of the sanding primer.  There are a few small spots that we have sanded thru the primer to bare metal in the final sanding.  I was advised to spray those spots with an etch primer before spraying the basecoat.  Can someone confirm that this is what I want to do?

[anlauto]

Are you going to do any type of guide coat to assist with the final blocking ?

[GoMangoBoys]

Yes.  I am using it to identify low spots and fixing them with either more primer, or the icing filler.

[BFM_Cuda]

I would use a little etch primer to cover any spots you have burned through to metal, and use a sealer coat before the base coat.

[anlauto]

Yes.  I am using it to identify low spots and fixing them with either more primer, or the icing filler.

[kawahonda]

I am not aware of any base coats that are compatible with "etching" primer. Trust your technical data sheet and not a forum. OMNI and PPG base coats that I have seen are NOT compatible FYI. Etch coats are acid-based coats. Will it work? Probably. Will it last without question? Risky. Etching primer has limited uses IMO.

Did you burn through bare metal during your block sanding (typically 180 grit) or during wet sanding (typically 400-600 grit)?

Restorations will typically need two high-build sessions minimal for a "quick" good job (or if you are very experienced can produce a "quick" and perfect job). One for block sanding (180 grit, which will expose bare metal), and one for "paint work" or final sanding (400-600 grit) which will also expose bare metal. Need to know the stage you are on. Assuming you are on the "second" stage, then during your spray-day, you need to NOT use etching primer, and REDUCE epoxy primer, shoot a single wet coat or so, wait 1-2 hours (depending on shop temps) and then shoot your BC/CC. I'm 95% sure I'm right here.

Glazing putty is awesome, but for my car I would never trust my glazing work without at least 1-2 more coats of reduced high build on top followed for a final wet sand for a perfect finish. I don't go less than perfect, but that's me.

I want to make sure you do not use etching under basecoat/clear coat without reading your sheet and look under the compatible substrates and confirm...

[Rbob]

My 2c. 

Skip the etch primer, a couple coats of epoxy primer(spot priming non-sanding type and 2nd coat out a little further than the first) ) but let it dry and add some guide coat and #320 grit to correct the imperfection.

On edit, you have went to a lot of trouble to build a nice car, I would put 2-3 more coats of high build primer on the whole car, guide coat and block with 220 just enough take take most of the guide coat off, add guide coat again and sand with 320-400 and get ready for sealer/basecoat and clear coat.


Southern Polyurethanes epoxy primer
https://www.southernpolyurethanes.com/epoxy-primer

https://www.southernpolyurethanes.com/perfectpaintjob

or Tamco's High build DTM  or DTA Epoxy ..

https://tamcopaint.com/collections/primers/products/dtm-primer

Collision Repair Shop since 1985

[Rdchallenger]

I'm currently in the same stage as you as with blocking... I did 220 for my first, and have just added another coat of high build after spotting the bare spots with epoxy primer for protection. After this session of blocking I will again spot any bare spots with epoxy and high build again to which I will then hit with 340. I'll repeat the process yet again before wet sanding with 400.

I'll then use an epoxy sealer tinted with my base and then spray my actual paint.

This work will all be done just so I can hit it with single stage so it is factory correct. But again that's just a preference of mine to go SS over BC/CC.

[jimynick]

While I validate your preference to put SS paint on your car, the question in my mind, is why go to the length you've gone insofar as prepping the car for BC/CC? Is the colour you're painting non-metallic? Will shooting it in SS disguise the fact that it now likely has better fits, prep and finish than any original car, but not the paint? Just curious. 

[Rdchallenger]

While I validate your preference to put SS paint on your car, the question in my mind, is why go to the length you've gone insofar as prepping the car for BC/CC? Is the colour you're painting non-metallic? Will shooting it in SS disguise the fact that it now likely has better fits, prep and finish than any original car, but not the paint? Just curious. 

A few different reasons honestly. Green-Go so none metallic, I'm afraid I'll run the clear something fierce, price, and I'm not looking for that deep deep shine that the car didn't come with.