randytrish

I thought I would try here first on advice on sanding and buffing out clear coat on a few parts I've recently painted. So here's the story. I recently purchased a aerokit 1 rear spoiler and deck lid for my 993. I decided to try and refinish it myself. I painted it with dupont chromabase base and dupont chroma clear. I was lucky to get a perfect color match. The base coat went on fine. When I went to do the clear I couldn't get it to cover everywhere without leaving a sort of textured, ripple finish. I'm not necessarily concerned with what caused it as much as the steps I need to do to sand and polish the clear coat smooth. I did this paint experiment for a couple of reasons. 1. Can I do it. 2. Is it worth the hassel to do it or just pay someone.
Thank in advance,
Randy

earossi

Sanding out the clear coat is fairly straight forward, but requires a light touch and your patience. It is not clear from your posting how much clear you were able to lay down. Assuming that you got 3 to 4 coats to cover, then you should be ok to color sand.

First, give the clear time to cure. Some shops will wet sand the car after a day; which is not best. I would give your paint job about a good week to cure well, if not two weeks.

You do the wet sanding in stages, starting with a coarse grit and then working down to a very fine grit. I would suggest starting out with 800 grit of a good quality wet/dry paper (like 3M). Then you will progress to 1200 or 1500 (whatever is available), and make the last sanding with 2000 or 2500 grit paper, followed by polishing.

When sanding, use a block form for the paper......not your fingers or the palm of your hand. You will want to control the pressure on the paper to very little without pushing hard on any small portion of the paper. You can buy a "Durablock" from your paint supplier; or, you can make an equivalent out of wood. You can also use the wooden stir sticks supplied with your auto paint as a form for your paper.

You will cut your papers to wrap around the stick tightly so that the paint is presented a smooth and flat sanding surface.

You must do the sanding with the paint ALWAYS wet. I usually use water with a very small amount of car wash soap (like a cap full per one gallon of water). The car soap will provide the lubricant for the paper to slide across the paint surface. Use a quart sized pump sprayer to spray the water/lubricant onto your work area.

Do the wet sanding with the block moving at about a 45 degree angle to its centerline. Begin by swiping the angled block up to the right at 45 degrees and then do a swipe to the left at 45 degrees. This alternate approach will allow you to use all of the wrapped paper and will prevent you from going to thin in any one area.

Use practically NO pressure on the sanding block. Begin by flooding the area with water/lubricant and then perform your sanding in nice slow steps, alternating each swipe with the block to the right and the left. You want to provide just enough pressure to just begin to feel the sandpaper cut the surface.

Using the 800 grit, sand the surface until, to the eye, you have gotten rid of all the orange peel that you can easily see. Some may still remain, but will be picked up with subsequent sanding steps.

Continue to flood the sanding area as you go and occasionally wash down the entire panel to see how you are doing.

Once you have completed your work of knocking down the visible imperfections in the paint, switch your paper out to 1200 or 1500 and continue as before; however, you are now at a point where you are just attempting to remove the sanding marks from the 800 grit paper, so use even less pressure since your painted surfaces should now be flat. Continue to wet sand for two to three minutes per area and then change your paper out to the 2000 or 2500 grit paper and continue the sanding process. Before using the 2000 paper, carefully wash down the area to be sanded to get rid of any debris that could scratch the paint as you complete the wet sanding process.

Once rinsed, complete the wet sanding using water and the 2000/2500 grit paper. Until the surface is uniform in visual appearances. This final sanding step should go very quickly.....say 1 to 2 minutes per painted area.

Complete the sanding process by washing the complete area to remove all debris left over from the sanding.

Visually, your clear coat will appear "unclear" and very dull......no shine at all. But, don't panic, because polishing will bring back the shine.

To polish out the sanded paint, you'll need at least two steps depending on whose products you use. I currently do the initial polishing using Mernzerna Intensive Polish on an orange pad fitted to my DA orbital polisher. Follow this up with Menzerna Nano Finishing Polish on a green pad and your paint should look fantastic. You can then seal and/or wax the finished surface to preserve it.

3M and Maguiar also offer a line of polishing products to achieve similar results.

At any rate, this is what has worked for me. Others may have additional advice that can improve on what I do.

randytrish

Thanks Ernie,
I should have plenty of clear on the pieces. I was somewhat familiar with the process. I wasn't sure of the grit level from start to finish. Also I wasn't sure of the cure time. Unfortunately there's not many areas that I can use a block on due to all of the curves. I have a orbital buffer. I'll need to get the correct polish and pad.
Is there any advantage to leaving these pieces in the sun (hot, near 100) to cure?
Thanks again,
Randy

earossi

The curing to catalyicised paint is a chemical reaction which takes time to occur. I'm not certain if high temps promote faster cures, but would have to believe that hot is better. I would still wait a couple of days, minimum, with the car setting in the sun before you do the color sanding.

If you are dealing with lots of curves, just orient your sanding block to the flat side of any curves. That is also the advantage of using a thin sanding block like a stir stick - the stick will bend somewhat to help you through the valleys of curves. You could also think about using a shorter section of block, but should stay at least 3 to 6 inches in length. The main purpose of the block is to spread the pressure uniformly over the sanded area to minimize any cut through.

When I repair rock chips, I just mound up the color coat to slightly above the surrounding surface and then block sand it just as I have described to you with the exception that for small blemishes I have cut some 2 inch long blocks out of 1x1 wood. That allows me to confine my work to just the adjacent area of the blemish I am attempting to fix. The process works great.

Lastly, if you painted any edges, try and minimize the time of the orbital in that area, or you may cut through. That goes for both the sanding and the polishing.

Keep in mind also, that as long as you don't damage the base coat, you can re-coat the clear if you are unhappy with your finishing results.

TOGWT

Fresh paint can be polished or wet-sanded after approx 24 hours. Be cognizant that solvents can cause problems with new paint

TOGWT

Tools I use:

Preppin Weapon Sanding Block - Made out of high impact ABS plastic & is constructed in an ergonomic shape for complete comfort when sanding. The tough rubber pad that is firm for wet or dry use. Perfect for wet sanding as it's made from stainless steel and plastic and it floats in a bucket. It also has the best paper clamping system I've ever experienced and it's flat.

6-inch x 4-inch sheets of Nikkens™ 2000, 2500 and 3000 - grit finishing soaked for at least 30 mins (better soaked over-night)

3M™ Wetordry™ Rubber Squeegee, P/N 05517, 2 -inches x 4 -inches) is the best tool for checking your progress.

Lots of water and Gloss It EVP Pad Prime for surface lubrication; always ensure you are wet-sanding a truly wet surface

earossi

Randy,

Out of curiosity, I did a "Search" of the forum for past threads on color sanding fresh paint. Most of what I found compliments what I told you (and there is a lot out there if you do the Search). However, many of the posters recommend using finer grit paper to start out with than I suggested. So, you might want to take their advice just to safeside your work. Many posters recommended starting the sanding process using 1500 or 2000 grit wet/dry paper, and finishing up with 2500. I believe that this will take longer to execute, but will be safer for you if you don't have that "light touch" I was referring to in my posting.

The other thing that I forgot to suggest is that you take your sand paper and pre-soak it in water for about 10 minutes before you start sanding. That assures you that the paper is "wet" before you start so that if you don't flood the area properly, as I had advised, at least your paper starts out wet! Another safeside.

Let us know how your work comes out.

MoeMistry

Great advice Earnie. Nice thread.