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can i wet sand nason 2k building primer? i put on 3 coats
used the da and hand sanding put on 2 more coats now i want to wet sand will it hurt anything?

If it consisted of an "A" part and a "B" part I sincerely doubt it would hurt anything. It's just about bullet proof at that point. I used Southern Polyurethane's equiv and after 1 week of drying they recommend sanding whether it be dry or wet. I wet sanded my frame after 2k and it smoothed it out nicely.

Keith

Philipt,

Aren't you going to cover your primer with a finish coat of paint? Wet sanding 2k will work, as long as you don't go through the finish, but it sure won't leave the proper "tooth" for you final color coat.

Dry sand with something on the order of 320 or 400 would probably be more than adequate...unless you are going to run the rig down the road in primer.

The final color coat needs something to hold on to. That's how I see it.

Stuart

atomarc, the number of answers that i get on this subject is
amazing. would you use the da or hand sand. oh yes it will be painted

Philipt,

I'm not a professional painter. I would hand sand the 2k primer dry with 320 and shoot the color. All your bodywork should be finished by now. The 2k seals the substrate and when sanded give a means of adhesion between primer and finish coat.

If you sand through the 2k with a DA or whatever, you are back to square one...bare metal that needs to be addressed. The 2k should be as perfect as the finish coat is, it just needs tooth to allow the finish coat to hook to it.

This is how I see it in my minds eye!

Stuart

Could someone please explain to me why sanding with water would yield a different "tooth" than sanding dry with the same grit?

I always thought wet sanding was just a way to keep the paper from loading up... but that was 35 years ago.

Has sanding changed?

Hey Brother Woody..I can't give a scientific reason why but wet sanding does feel smoother to me..My best guess is that the water(or soap and water) acts as a lubricant. Now.........Provided you don't use too fine a sandpaper I think the tooth for painting should be fine..no need to go past 320-400 though

about 30 years ago I had my 1967 firebird painted at Maaco..I did the body work prior to the paint job and wet sanded it to 600...it was actually shiny..the first thing Maaco did was to rough it up...

Keith

Woody,

I might have typed before I 'thunk'...you're absolutely right, aside from helping with paper loading, the water shouldn't make much difference in the feel or finish.

Having said that, I sort of agree with Keith. Wet sanding somehow seems to make the sanded surface feel smoother. I'm neither a scientist or a professional painter so I don't know for sure.

Stuart

My opinion based on discussions with the PPG guy and painting various projects over the past 25 years.

Paint needs "tooth" so it wont come off when you hit it with the hose when washing. I generally dry sand using the DA and 280 - 320 grit paper. Then apply color and clear. If I did it right, the clear is near perfect (happens only 3 out of 10 times). If I sneezed when applying, then I can wet sand and buff the clear. If you sneeze during the color coat, then wait 4 hours and wet sand and tack prior to spraying clear.

Scott

It's been a long time since I've used a paint gun so I can't comment on product specifics of new materials BUT the basics should be the same.

The required "smoothness" of the finish of the base coat prior to topcoating depends on the requirements of the topcoat. The sanding serves two purposes. One it creates a more level surface, removing high spots for a smoother topcoat. Second it creates grooves in the surface which increases the surface area for the topcoat to bond too, increasing the "tooth". It may feel smoother but if you could look at it under a microscope you would see them.

On the old acrylic lacquer I shot I couldn't use anything rougher than 600 grit or the sand scratches would swell and show in the topcoat. The enamel we shot would peel if we used anything finer than 400 (preferably 320) because there wasn't enough "tooth".

Paint is nothing more than a pigmented adhesive. All adhesives I'm aware of require a roughened, etched or sanded finish to bond correctly.

If your going to use a sealer before top coating it doesn't make any difference if you wet or dry sand.I prefer wet sanding useing a rubber squgee inside the sand paper to keep the paper flat and use the squgee to remove the water and look for inperfections. I think that sanding marks and low spot are much easier to spot that way

Paul