Takin' a Crack at Wet Sanding & Polishing

[GG Allin]

I had (have) every intention of having my M3 repainted at some point. The car has been sitting for three years now. And I've recently started putting back together. I plan on driving it a little next summer.
But in the meantime I decided the best way to learn how to wet sand and polish paint is to jump right in and do it. No big deal if I make mistakes on this car at this point.
I started with a 600 grit then 1000, 1200, & now I'm up to 1500. I plan on finishing the sanding with 2000 then 3000.

Beyond the wet sanding I have a Porter Cable 7346 random orbital that I plan on polishing with. It spins up to 6800. Was going to use Meguiar's M105 and then M205.

Also, I'm looking for a good sanding block. the 3M one on Amazon has horrible reviews.

1/4 panel through 1200 grit.

Any advice is appreciated.

[Oh Haha]

Keep the buffer moving at all times and stay away from edges. Looks like you've got a good start so far.

I'm not an expert but I have painted and wet sanded/buffed out fresh paint and done spot repairs that turned out nicely.

[Scott Douglas]

I'd say you're spending a lot of energy needlessly with going over it with 3000 grit.
The polishing compounds should work on the 2000 surface just fine.
If you were saving the paint job I'd recommend taping the edges too.
My son did my old 912, it turned out pretty nice.

[1990C4S]

3000 grit is show car quality.

[GG Allin]

Originally Posted by Scott Douglas

I'd say you're spending a lot of energy needlessly with going over it with 3000 grit.
The polishing compounds should work on the 2000 surface just fine.
If you were saving the paint job I'd recommend taping the edges too.
My son did my old 912, it turned out pretty nice.

Reading various sources on the subject it seems up to 1000 grit you're flattening the clear coat. Above 1000 you're polishing. Some will sand up to 5000 just to make the buffing easier.

[Scott Douglas]

This is the stuff my son used.



I'd say we got the results we hoped for.

[Charles Freeborn]

Old body mans trick- put a dash of dish soap in the wet sand water. Keeps the paper from loading. The new foam backed abrasives are great. My favorite block is a "dura-block". Get them at the auto paint store.

[bobrestore]

if you search you will find 3M on line videos of how to use their products... their hook and loop products for color sanding cuts the work substantially... do not burn... use a spray bottle and keep it wet.... also if you tape of , do not "work" a lot on the tape area. otherwise when you pull the tape you will see a line.... unfortunately removing this line will be next to impossible.

[Willem Fick]

Originally Posted by Charles Freeborn

Old body mans trick- put a dash of dish soap in the wet sand water. Keeps the paper from loading. The new foam backed abrasives are great. My favorite block is a "dura-block". Get them at the auto paint store.

A really good tip this!

[speeder]

I have a little experience in this, (not a lot), the only thing I'd add is that 600 is too rough for anything you're doing on auto paint. I started a thread once when a friend gave me an old Mercedes-Benz with REALLY bad paint.

He'd gotten ripped-off on some body work and the hood looked like it was painted w a brush and a nappy roller. The trunk and roof had profound scratches in the clear coat from boxes being stored on it and dragged across, etc. Since I had nothing to lose, I just got some sand paper and soapy water and went at it. Came out pretty good, I think nothing of taking sandpaper to a car now as part of normal detail job. But not 600.

Here was that thread:

Adventures in Auto Detailing:

[Shaun @ Tru6]

I would not have started at 600, that is way too rough. I would have gone 1000 by hand and then jumped to Trizact 1500 with a random orbital sander (very low speed) and interface pad and then 3000 and then blended edges with 5000 since your car is dark.

Then I would use 3M's Perfect-It system first with compound, then machine polish and then with ultrafine machine polish, again because your car is dark.

[GG Allin]

I've already learned a lot here. Now I consider it a challenge to get the finish back having potentially serious screwed up using the 600. I have some supplies en route via Amazon. Some more stuff "saved for later". From here on out, no more 600.

The idea of wet sanding with an orbital polisher is interesting. Until recently I had no idea that was even something you could do.

[sugarwood]

800 and 1000 will correct the 600 grit. You're fine, as long as clear is still there.
Please take and post lots of photos.

[Shaun @ Tru6]

make sure you are crosshatching at 45 degree angle with 800/1000 to get the 600 scratches out correctly.