car painting - PeachParts Mercedes-Benz Forum

hawthorne90250 · #1 11-05-2007, 01:03 PM

Hi
I am about to prep my car for painting. i am going to remove the trim, and sand the car. i have no rust and would like to know what sandpaper to use and any special techniques. i want to prep it good before having some one paint it.
Thanks

KarTek · #2 11-09-2007, 10:40 AM

This is quite an undertaking as the prep is key to a good finished product. It's hard to cram a thorough explanation into a small space but I'll try. It takes years of experience to do it right but here are the basics:

This process assumes you have no rust or that you have completely finished any other body work.

1. After you remove all the trim, thoroughly wash the car.
2. Go buy yourself some 600 grit wet sand paper. It HAS to be wet. Also pick up a rubber sanding block. The full sized sand paper sheets will tear down into sections that fit the sanding block.
3. Get yourself a bucket of clean water and place a sheet of sand paper in it about 20 minutes before you intend to start sanding.
4. While your paper is soaking, put on some old clothes and shoes becuse the sanding process will sling wet crap all over you.
5. Attach a piece of paper to the block and take your hose and turn it on to a trickle.
6. Holding the hose in one hand and the sanding block in the other, trickle the water onto the car and begin gently running the block over all the flatter surfaces of the car. Use the flow of water to wash away the debris generated by sanding.

If you feel at any time a "squeak" under the block, stop, and rinse the block and the surface thoroughly and continue sanding. The whole idea here is to make the whole car dull looking as though it's been painted with flat paint with no shiny spots. Also, don't run the block over corners and ridges as you will take the paint all the way off down to the bare metal and that's not good... You'll have to prime and re-sand if this happens.

Once you've worked all the flat surfaces, take a piece of sand paper in your hand and go over all the curved surfaces and all the nooks and crannies. This is the part that separates the pros from the amatuers. You have to thoroughly sand every crack, crevice and louver - all the way into the corners and where every piece of sheet metal is joined. If this is not done correctly, the paint will have a tendency to peel out of these areas because of poor adhesion.

That's the best description I can give. Take your time and be thorough.

TX76513 · #3 11-09-2007, 10:44 AM

Kar Tek gave a good description. If you are more of a show-me person (and I suggest this if you have never prepped a car) go over to youtube and do a search for auto + painting. There are some good video examples of prep work. Remember as stated above this is the most critical part of your new paint job.

KarTek · #4 11-09-2007, 10:48 AM

Agreed, this is the kind of thing you really can't describe in words. Someone has to demonstrate it for you. That's how I learned... My buddy said: "here, take this and do this..." on an old car.

TX76513 · #5 11-09-2007, 10:58 AM

He will soon understand the easy part is shooting paint on the car.

Whiskeydan · #6 11-09-2007, 11:03 AM

Its a good idea to wash the car, paying attention to those nooks and crannies, with a scotchbrite pad, warm water and a small amount of tide detergent. Getting all the wax and oils from the paint prior to sanding will prevent loads of paint problems.
Wash around the fuel filler area very well.

Touch up any chips prior to wet sanding.

Tuck a small rope under the rubber windshield seals lifting them to allow you to prep and paint beneath. Common place for peeling.

Whiskeydan · #7 11-09-2007, 11:07 AM

Quote:

Originally Posted by TX76513

He will soon understand the easy part is shooting paint on the car.

Unless it's silver. My 300D is almost ready to shoot after many months of very hard work. I shot the hood myself while it was off the car. It turned out very slick however, there's light and dark areas so it's getting sanded back down then off to the pro with the rest of the car.

TX76513 · #8 11-09-2007, 11:14 AM

Quote:

Originally Posted by Whiskeydan

. My 300D is almost ready to shoot after many months of very hard work. I shot the hood myself while it was off the car. It turned out very slick however, there's light and dark areas so it's getting sanded back down then off to the pro with the rest of the car.

Were you using a canister gun? I had a similar result on a hood. Going to use the remote hose gun next time....live and learn.

ARINUTS · #9 11-09-2007, 11:15 AM

I still want to see the Maaco paint job.

Whiskeydan · #10 11-09-2007, 11:20 AM

Quote:

Originally Posted by TX76513

Were you using a canister gun? I had a similar result on a hood. Going to use the remote hose gun next time....live and learn.

HVLP gravity feed.
The problem lies with the metalics in suspension. You have to keep the paint agitated and fog on thin coats of base. I did pretty good but not good enough for the effort that has gone into the prep work.

TX76513 · #11 11-09-2007, 11:22 AM

were you shooting anthracite metallic gray?

Chuffer · #12 11-09-2007, 11:27 AM

Another trick is to add a drop or two of dish soap to the bucket of water that you are rinsing your 600 grit paper in. The soap helps prevent build up of material on the paper and helps with material removal from the painted surface. Just a drop or two in a gallon of water is enough. Too much and you'll have suds.

Whiskeydan · #13 11-09-2007, 11:35 AM

Quote:

Originally Posted by TX76513

were you shooting anthracite metallic gray?

735 silver, Omni AU base, clear. However, Talking to a very good painter friend I find the Omni clear has little UV protection. He is willing to buy my Omni clear for use on door jams and protected areas where it sees little exposure. I'll spend more for a better clear coat.