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PostPosted: Wed Mar 13, 2019 5:25 pm
As I mentioned earlier, guide coat is your friend and will let you know if you're ready for color or not.

I would shoot the 2k primer, guide coat it and then block sand just to remove the guide coat. If it looks good shoot your next coat of 2k, add some guide coat and wet sand with P600 until guide coat is gone. Clean it good and you are ready for sealer (optional) and color.

If you are not all that concerned about getting it perfect, then shoot your 2k primer and wet sand with P600 then shoot a reduced coat of 2k as a sealer prior to shooting your color.
1968 Coronet R/T


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PostPosted: Tue Mar 26, 2019 6:54 am
68CoronetR/T, yes I should have mentioned that I started guide coating once I got down to 180, I should have done it it with 80 grit but now I know.
So now I'm running in to some issues, I got all surfaces down to 400 with a guide coat but had broken through to some filler spots, laid down another coat of H/B primer, sprayed guide coat sanded again with 400 but by the time I get down to the bottom of the orange peel there is not much left of the H/B primer I just sprayed.

I have sprayed two coats like that now and 90% of my expensive primer is on the floor by the time I have it sanded flat and smooth, is that just parr for the course or is my spraying technique wrong?

I am spraying white primer on white primer and am having a hard time seeing the coverage I'm getting so ending up with some thin spots between passes.
Can I spray a light guide coat first before laying down a coat of primer just so I can see that each pass is completely covering?

I've been doing some experimenting to try and avoid wet sanding, if I sand with 400 dry then with 600 dry then scuff well with a 3M grey pad I can get what looks like to me a smoother more reflective surface with no visible scratches than with 600 wet.
Is that a valid method?
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Chris



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PostPosted: Wed Mar 27, 2019 6:26 pm
No one?

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PostPosted: Fri Mar 29, 2019 8:15 am
Hopefully the Mods will see your cross posted new thread and remove it.

A few issues here.

Firstly if your orange peel is so high that getting to the bottom of it thins the primer to the point of almost seeing through, or, in fact, rubbing through, then you really need to address your spraying technique. Hold the gun in closer so you're spraying wetter and you'll better be able to see where you've just been and make the next pass with the correct overlap. Move your head so that you can see what is happening as the paint hits the surface.

The other thing I'd be concerned about is whether your substrate is, indeed, flat. Maybe you're exposing high spots that need to be corrected so that when you do prime you're going to be able to sand evenly. Cross hatching your sanding pattern. with guide coat should show this up.

By comparison with base coat and clear, primer is cheap. That some of it ends up on the floor is inevitable, but better that you get it right now than find out later and have to rework the panel(s).

Dry sanding your primer is an acceptable alternative and P600 dry should be roughly the equivalent to P800 wet. Be very sure that you've taken out all the P400 scratching though. If left this will ruin your final result.
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PostPosted: Fri Mar 29, 2019 5:28 pm
NFT5 wrote:Hopefully the Mods will see your cross posted new thread and remove it.
Thanks NFT5, I was getting desperate to figure out what I'm doing wrong.
A few issues here.

Firstly if your orange peel is so high that getting to the bottom of it thins the primer to the point of almost seeing through, or, in fact, rubbing through, then you really need to address your spraying technique. Hold the gun in closer so you're spraying wetter and you'll better be able to see where you've just been and make the next pass with the correct overlap. Move your head so that you can see what is happening as the paint hits the surface.
I think my real problem is I don't have enough light so can't really see my coverage and I'm getting thin areas that sand through easier than the areas with a proper thickness of primer. More strip lighting and work on my spraying technique. I find I'm all pumped up when spraying and it's making me rush.

The other thing I'd be concerned about is whether your substrate is, indeed, flat. Maybe you're exposing high spots that need to be corrected so that when you do prime you're going to be able to sand evenly. Cross hatching your sanding pattern. with guide coat should show this up.
I'm pretty sure it's flat, I'm using the long slightly flexible Durablock with sticky sand paper, almost all of my sand throughs are on the edges and body lines of panels.

By comparison with base coat and clear, primer is cheap. That some of it ends up on the floor is inevitable, but better that you get it right now than find out later and have to rework the panel(s).

Dry sanding your primer is an acceptable alternative and P600 dry should be roughly the equivalent to P800 wet. Be very sure that you've taken out all the P400 scratching though. If left this will ruin your final result.
That's good to know, if I do feel I have to use wet sanding I have read that all wet sanding strokes must be in one direction only, is that generally how you Pros do it?



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PostPosted: Sun Mar 31, 2019 5:45 pm
I mounted a couple more big lights and held the gun closer, that fixed the pebbles and orange peel but produced some runs so next time I'll have to reduce the volume or move a little faster.
I had some idea that there would be water every where if I wet sanded, it was fine, just a few drips really. So I have about half the car wet sanded with 600 now and those fluorescent lights are looking pretty straight in the wet reflection!

Question about the sealer, the Besacar Urki urethane primer I'm using says a max of 10% reducer to use as a sealer. That 10% doesn't sound like much, maybe I just don't understand the chemistry, is 10% standard?
Also, once my final coat of sealer is on before colour, can I wet sand the sealer with 800 to flatten out or is that not allowed?
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PostPosted: Sun Mar 31, 2019 6:57 pm
grannyknot wrote:and held the gun closer, that fixed the pebbles and orange peel but produced some runs so next time I'll have to reduce the volume or move a little faster.


Usually moving a little faster is the solution.

grannyknot wrote:That 10% doesn't sound like much, maybe I just don't understand the chemistry, is 10% standard?
Also, once my final coat of sealer is on before colour, can I wet sand the sealer with 800 to flatten out or is that not allowed?


Some primer/surfacers are thin to start with, so not much reducer, if any, is required. If the TDS says 10% maximum then follow that. Yes, you can wet sand, if needed.

grannyknot wrote:if I do feel I have to use wet sanding I have read that all wet sanding strokes must be in one direction only, is that generally how you Pros do it?


Generally I keep the block in line with the panel, i.e. horizontal on vertical panels, but move it +/- 45 degrees. This ensures that you don't wear a track in the line of the block.
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PostPosted: Sun Sep 15, 2019 6:13 pm
The car is finished, as always thank you guys for the help, really appreciate it.
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