# Technique for Wet Sanding



## jmlapoint (Sep 4, 2008)

I have done a lot of sanding and polishing, but never *'Wet Sanding'.*
I have lots of Silicone Carbide Waterproof Sandpaper.

Does anyone have a technique for Wet Sanding, and is there an advantage to this technique?

Thanks.

John


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## Uncle Grumpy (Jul 25, 2005)

jmlapoint said:


> I have done a lot of sanding and polishing, but never *'Wet Sanding'.*
> I have lots of Silicone Carbide Waterproof Sandpaper.
> 
> Does anyone have a technique for Wet Sanding, and is there an advantage to this technique?


What are you sanding? I'm going to assume aluminium or paint on a frame.

Wet sanding is simple, you wet the silicon carbide paper and work away as per normal. The wetting helps with friction and stops the paper from clogging, especially when painting. probably not so critical for sanding aluminium for polishing, especialy at the start when using coarser grades.

Grumpy's hot tip? Glad you asked. A short squirt of dishwashing liquid into the water helps to keep things flowing smoothly.

I also use WD40 if I'm sanding aluminium for polishing, especially when getting down to the finer grades prior to polishing.

Grumps


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## Mr. Versatile (Nov 24, 2005)

I've done it some. When I retouch my bike I usually wet sand the spot I painted. I use either 1000 or 2000 grit paper. Since the area(s) I'm going to sand are quite small I just tear off a small piece of the sandpaper & dip it into a small container of water. (Old Gatorade powder mix plastic jars are perfect for stuff like this.) I partially wrap the paper around my index finger, then gently sand using a straight line motion. I use plenty of water. When I can't feel any unevenness in the paint, I'm done. Here's a guideline I use for touching up paint.

1. Clean the damaged area thoroughly with alcohol.

2. Carefully inspect the chip or scratch to see that there is no chipping or peeling paint along the edges of the damaged area. If there is, take a sharp Exacto knife and carefully chip the peeling paint away until you have a clean edge that won’t lift.

3. Assuming you have found paint that matches, shake it up very thoroughly – very thoroughly. After you’ve done that, shake it up very thoroughly again. If you’re using nail polish you can skip this step.

4. Apply the paint using a small brush or a toothpick. If it’s a scratch or a chip the size of a half a pea, I’ve found the toothpick works better. Depending on the size of the damaged area you might want to apply several light coats instead of one heavy one. You can do this pretty quickly because the paint will dry within 15-20 min. Don’t be afraid to ”color outside the lines.” When you’re finished it won’t show.

5. After you’ve applied the paint it’s very important to inspect the area to make sure the paint you’ve just applied is HIGHER than the surrounding area. If it isn't’t – apply more paint until it is. It MUST BE HIGHER than the surrounding area.

OK! Here comes the “scary” part for most people.

6. Gently wet sand the repair using 1500 or 2000 grit sandpaper. If you have trouble finding it, look at an auto parts store. Be careful here! Go slowly. Don’t press hard. You don’t want to sand the paint off the surrounding area. Tear off a small piece of the sandpaper and dip it in a container of water. Your goal is to just smooth out and blend in the repaired area. Sand a little – check it---- sand a little – check it. Use plenty of water. Check to make sure the paint is level by running your fingertip across it. 

7. The paint will be “foggy” from sanding. Get some polishing compound (NOT rubbing compound). Rubbing compound is more abrasive than polishing compound. Polishing compound is almost always white, and comes in a can that looks like paste wax. In a small container put a finger scoop of polishing compound and some water. Stir it up. I like to get so it’s about the consistency of cream of tomato soup. Looser is better than too firm or thick.

8. Using the mixed polishing compound, dip the corner of a clean, cotton rag in it and gently rub the “foggy” area until shiny. Rub a little, wipe it off to check it, rub a little more, check it, etc.

9. Apply clear coat if desired. You may have to rub the clear out with the polishing compound as well.

10. You’re done.

One other thing that I find essential is Meguires Clear Plastic Polish #17. You won't find it in stores, so you'll have to order it from Meguire's web site. It's truly magical stuff. I use it after the polishing compound. Meguire's other plastic polishes / cleaners won't make any difference. It's got to be the #17.


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## jmlapoint (Sep 4, 2008)

Mr. Versatile said:


> I've done it some. When I retouch my bike I usually wet sand the spot I painted. I use either 1000 or 2000 grit paper. Since the area(s) I'm going to sand are quite small I just tear off a small piece of the sandpaper & dip it into a small container of water. (Old Gatorade powder mix plastic jars are perfect for stuff like this.) I partially wrap the paper around my index finger, then gently sand using a straight line motion. I use plenty of water. When I can't feel any unevenness in the paint, I'm done. Here's a guideline I use for touching up paint.
> 
> 1. Clean the damaged area thoroughly with alcohol.
> 
> ...


MR. V;
Thanks so much for this great info.
I am trying to do 2 projects.
1. Repair and repaint a black Jeep Hood that has some paint corrosion, but no dents or scratches.
2. I am also trying to polish an old Cinelli Stem. If I use 220-400 paper I get scratches but make good progress removing anodizing. If I use 600-1500 paper I get no scratches but takes forever. Thought by using water, I could use a coarser paper and not get the scratches.
Again, thanks so much.

John


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## jmlapoint (Sep 4, 2008)

Uncle Grumpy said:


> What are you sanding? I'm going to assume aluminium or paint on a frame.
> 
> Wet sanding is simple, you wet the silicon carbide paper and work away as per normal. The wetting helps with friction and stops the paper from clogging, especially when painting. probably not so critical for sanding aluminium for polishing, especialy at the start when using coarser grades.
> 
> ...


UG;
Thanks so much.

I am trying to polish an aluminum Cinelli Road Stem and not get scratches, but make progress.
The finer papers don't leave scratches but removing the anodizing takes forever.
I thought I could use a 220-400 paper with water and make progress and avoid scratches.
Never did wet sanding before, and I think I will try both Dawn and WD-40 on my stem.
Again, thanks so much.

John


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## Amfoto1 (Feb 16, 2010)

No, use finer paper when wet sanding....

Yep, like Grumpy said... Put some dishwashing soap into a bucket or spray or squeeze bottle then fill it up the rest of the way with water. Frequently wash the area with it, to rinse off the paint you have removed. You'll see "mud" coming off the surface very quickly. The soap helps "lubricate" the sandpaper.

Wet sanding removes material _much faster_ than dry sanding. So, start with a finer paper. Watch out for high spots and ridges... You'll find yourself staring at bare metal in no time, if you aren't careful. 

I probably wouldn't use any coarser than 400 grit on the Jeep hood... if your intention is to prepare it for new paint. After it's smooth, go to 800 grit to remove any scratches from the initial sanding. You might need to go to an even finer grit again. This sort of depends upon the paint you will be putting onto it. Ask whoever is supplying the paint, or look for directions on the can or at the paint manufacturer's website. If using a primer, you might be able to leave off with a coarser sanding, with more "tooth" remaining. Spray the primer on, let it dry, then wet sand it with the finer paper before putting on the finish coat(s). Some paints, you use an even finer grit to wet sand between several finish coats of paint. 

If you just want to put a new clear coat on, you might be able to sand the existing color coat with finer paper... probably 800 grit or finer. Your preparation has to be meticulous. Then, after the clearcoat has been sprayed on and dries, you will probably need to wet sand it with an ultrafine paper, maybe 1500-2000 or finer, then buff it out with one or more polishing compounds. This is sometimes called "color sanding"....

Please note that you have to extensively dry off and wipe down any surface that's been wet sanded, before you can apply any sort of paint or clear coat. Any moisture will ruin the new paint. There is a "tack cloth", often with bee's wax, used to remove every last speck of dust. Then the surface is wiped clean with a prep liquid. Sometimes lacquer thinner, other times more specialized preps might be used, depending upon what you will be spraying on. Ask the people supplying the paint. 

For large, flat areas, get a sanding block to hold the sand paper. If you just use your hand, you the high points on your fingers will rub through the paint unevenly. There are various shapes, sizes and types of sanding blocks. Ask at a local auto paint supply shop.

The Cinelli stem I probably wouldn't sand at all. I'd use buffing compounds and a polishing wheel. Buffing compounds come in various grits, too. Start with a coarser one, then progress to finer ones. You have to use one that's for aluminum, too. You can use a grinding wheel for polishing one or two small items, but they really aren't up to heavy duty polishing and the motor will burn out pretty quickly. You'll need a heavy duty polisher for serious polishing work. They have stronger motors and heavy duty bearings. 

If it is aluminum, it will need to either be anodized or clear coated, to keep it from corroding after it's been polished. Raw aluminum actually corrodes pretty easily.

P.S. Black is the most difficult color to get "perfect". It shows any flaws - like too coarse sanding underneath - amazingly well.


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## Mr. Versatile (Nov 24, 2005)

Somebody on the forums has a technique for removing anodizing from al parts. I think it involves oven cleaner, but don't hold my feet to the fire on this. Do a search. I think you'll find something. It has to a helluva lot easier than sanding it off.


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## jmlapoint (Sep 4, 2008)

Mr. Versatile said:


> Somebody on the forums has a technique for removing anodizing from al parts. I think it involves oven cleaner, but don't hold my feet to the fire on this. Do a search. I think you'll find something. It has to a helluva lot easier than sanding it off.


I seem to remember Dave H. posting this technique of removing anodizing with Easy-Off Oven Cleaner, but I haven't been able to locate it so far with a Search. Maybe I'm mistaken.

John


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## martinrjensen (Sep 23, 2007)

*Oven cleaner*

yes, use oven cleaner to remove the anodizing. Put it on and leave it on about 20 minutes or so. The hose it of and start buffing with a buffing wheel and some rouge on the wheel. Works great.


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## SilverStar (Jan 21, 2008)

Here's a good tutorial...from using oven cleaner to wet sanding to the final polishing:

http://prollyisnotprobably.com/2009/10/tutorial_polishing_bicycle_par.php


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## Blue CheeseHead (Jul 14, 2008)

jmlapoint said:


> MR. V;
> Thanks so much for this great info.
> I am trying to do 2 projects.
> 1. Repair and repaint a black Jeep Hood that has some paint corrosion, but no dents or scratches.
> ...


1.) Sanding is a stepped process. Start with a courser paper to remove material then move to progressively finer paper to remove scratches.
2.) For the hood of the Jeep, get a rubber sanding block like this one:










as you do not want any small pressure points. Body work is an art. You will want to feather it out significantly or a depression will show up when you paint it.

400 grit is about as fine as you want to go before painting as you want the base material to have some teeth for the paint to adhere to.


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## jmlapoint (Sep 4, 2008)

SilverStar said:


> Here's a good tutorial...from using oven cleaner to wet sanding to the final polishing:
> 
> http://prollyisnotprobably.com/2009/10/tutorial_polishing_bicycle_par.php


SilverStar;
Thanks so much for the link to the Tutorial. It is great, and just what I need.

John


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## rtarh2o (Dec 18, 2009)

Lots of good replies Amfoto1 has some good advice for the Jeep hood but I have to disagree with his choice of grit sand paper. 
I have painted many cars and very rarely use anything but 400 grit for the final sanding prior to paint. I usually start with 320 grit and finish with 400. I have tried 600 grit but honesty can't tell any difference in the final product between all of the above grits and the amount of sanding time is greatly decreased with the coarser grit paper. 
I imagine most production shops use 320 grit just to cut down on sanding time. 
From my experience 400 grit is about perfect, I would fear not having enough "teeth" for proper adhesion if using much finer than 600 grit paper.
Just my thoughts, check with your automotive paint supplier to make sure though.

Rusty


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## jmlapoint (Sep 4, 2008)

rtarh2o said:


> Lots of good replies Amfoto1 has some good advice for the Jeep hood but I have to disagree with his choice of grit sand paper.
> I have painted many cars and very rarely use anything but 400 grit for the final sanding prior to paint. I usually start with 320 grit and finish with 400. I have tried 600 grit but honesty can't tell any difference in the final product between all of the above grits and the amount of sanding time is greatly decreased with the coarser grit paper.
> I imagine most production shops use 320 grit just to cut down on sanding time.
> From my experience 400 grit is about perfect, I would fear not having enough "teeth" for proper adhesion if using much finer than 600 grit paper.
> ...


Rusty;
Thanks so much for your comments and info.
I really appreciate all the responses I have received.

John


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