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Discussion Starter · #1 ·
The only things that should be posted in here are your wet sanding techniques or direct questions about wet sanding.
Wet sanding is an effective means of removing defects that would require a heavy compound and a wool pad. The defect that people usually use wet sanding for is scratch removal. A scratch that can not be taken out safely with a wool pad and compound. Now, just a note, if you can catch the scratch with your finger nail, it most likely can not be fully removed without creating irreversible damage. Whatever you use it for however, you should be very careful in your judgment when debating whether or not to wet sand. You have to be able to remove those wet sanding scratches after you have removed the defect.
Wet sanding is safer in removing deep defects over a wool pad and compound because you have better control. If you try to use a wool pad and compound to remove a scratch and you accidentally hold it over the area for half a second to long, it will take off more clear than you wanted or it could even burn right through the clear. There is more predictability with wet sanding. It is a slower process, allowing you to more accurately gauge what you have accomplished and it gives you more control of how much clear is removed. Though again, you have to remember that you will have to polish out the sanding scratches out of the clear, so you have to leave enough clear to level those out.
What brand of paper and what grit to use? That is up to you for the most part. You just have to make sure that the paper you use was designed for wet sanding. Some paper will break apart in water. As long as the sandpaper indicates that it can be used in water, you are good to go. I don’t really recommend one brand over another, but I mostly use 3M Imperial Wet/Dry. I find that you can get it cheaper than most others, 3M is a reputable brand and it can be found locally in many locations. The only other paper that has impressed me enough to use again over 3M was the Meguiar’s Uni-grit. It seems to buff out a little easier than other papers since all the gritty pieces are the same size. However, you have to order it online and I hate the hassle of doing that. As for the grit you need to use, I wouldn’t suggest going under 1500, especially if you are just learning. For your first time, I would only use 2000 or higher. I rarely dip down to 1000 myself. I find that 1500 or 2000 does the job just fine and it buffs out easier. If I use 1000 or 1500, I stop about ¾ way though defect removal and switch to 2000 so I can smooth out the larger sanding scratches and so the area will buff out easier.
Before you wet sand, you have to make sure that you have the right tools. If you don’t, you are going to be extremely disappointed in the outcome and you will probably end up making an appointment at a body shop. These are the basics…
Sandpaper (water safe)
Sanding block (will explain later)
Bucket of water
Running water (optional)
Dish Soap (optional)
Machine Buffer
Appropriate Pads
Appropriate Polishes

Once you have determined that wet sanding is appropriate in your situation and that you have the right tools, you are ready to begin…
You want to soak the sandpaper you are going to be using for at least 30 min before you use it. This allows that sandpaper backing to become pliable. This will allow the paper to hug the surface better allowing a smoother coverage. Fill a bucket up with water. Preferably warm water. If you would like to, add a drop or two of dish detergent for added lubricity. (I would definitely recommend this if you do not use the hose technique explained below.) Drop the paper in and go eat a sandwich. If you want to, drop the paper in the bucket of water the night before so you are ready to sand first thing when you are ready.
The area that you will be sanding must be clean. Otherwise, you are going to create more damage that you want to do.
Once the paper has soaked and the area is clean, you are ready to do the actual sanding. I like using a sanding block. Now, I’m not talking about and expensive sanding block. I use a 25 cent flat PaperMate eraser. The pink ones. This is better than your fingers because when you use your fingers to sand, you actually make little uneven grooves in the clear. Can a normal person see it? Nah. Do you want it to be right? I do. If you just want the scratch gone and don’t care about minute little grooves, don’t use a block. Just remember though, it is only and extra 25 cents. Tear the paper into a piece that will cover the bottom of the black and will wrap to the top of the block.
Start sanding. You want to rub the paper in a back and forth motion. Don’t do circles and don’t cross sand. Just back and forth the same direction the whole time.
While you are sanding, you want to keep the surface wet. Keep dipping the paper into the bucket of water often. This serves two purposes. It cleans debris off of the paper and it helps you rewet the surface. However, if you have access to a hose and you are outside, I suggest that you let water slowly free flow out if the hose onto the area that you are sanding while you sand. This does the same thing as dipping it into the bucket, but it provides a constant water supply so your sanding motion and lube is uniform throughout the process. This is optional, but I highly recommend it.
You want to sand how ever long you feel safe in sanding. I can’t tell you a certain amount of strokes it takes to remove a defect. It depends on many variables. Paint hardness, singles stage paint or base/clear paint, sandpaper grit, pressure on the paper, dish soap lube or not, defect depth, etc…This is where practice and experience come into play. You really need to practice on a test panel before you try it on yours or someone else’s cars. If you don’t want to practice first, don’t get to aggressive.
After you have sanded, you want to clean and dry the area. Run water over the sanded area and then dry it with a clean towel (cotton terry or microfiber).
Once you have sanded until you feel satisfied, you are ready to buff out the sanding marks.
This is where my sanding pretty much DIY ends. You need to be somewhat skilled in using a buffer in order to perform the next step.
Some people ask if sanding marks are removable by hand. Well, I hope you have the endurance of a pig making love. (Google that.lol) It will take you forever to buff out sanding marks by hand and you will never get the results you want. If you don’t have a machine buffer of some sort, don’t even try to wet sand.
Other people ask if using a Dual Action polisher is enough. If you used 3000 grit and you have a cutting pad, the appropriate compound and some time... it is possible on some cars. I have buffed out 2500 grit marks with a PC 7424 before, but I had to keep going over the area and it was on softer paint. If you are working on hard paint, it probably isn't going to happen. I had a rotary backing me if it didn't. If someone were to ask me if they should try it, I would tell them no. This goes for all of the PC 7424 knockoffs. Ultimate Detailing Machine and the Meguiar's G100.
They now make higher performace versions of the PC 7424 and it's knockoffs. They have a PC 7424XP and the Meguiar's G110. Both have more power than the previous versions. I am unsure at how effective those are at removing wetsanding scratches. I would be more inclined to try doing it with them than I would with the regular versions, though.
There are getting to be so many machines on the market these days that mimic the PC 7424 that I would have trouble finding them all and saying if they would work or not. So, what I am going to say is this... If you don't have a rotary and you haven't had any experience wetsanding before, I wouldn't try it unless you know someone that can fix it or have access to backup tools like a rotary and know how to use them.
A rotary buffer, cutting or wool pad and the appropriate polish are needed to effectively remove the sanding scratches. You can tell if a polish is appropriate or not because it should say “Will remove 2000 or finer sanding marks at #### rpm.” or something similar to that.
Good luck and happy sanding.


Modified by 67Customs at 12:31 PM 8-4-2009
 

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Re: DIY - Wet Sanding Basics (67Customs)

Great write-up. Easy to follow.
I'll be using a PC 7424 and my highest cutting pad is a yellow. Most abrasive compound I have is Optimum compound. From experience, would this combination be aggressive enough to buff out the wetsanding marks?
Also, when you are done wetsanding and buffing out the scratches, do you top the area with anything additional/unusual or simply carry on with your detail as normal?
Thanks,
Kev
 

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Nice write up. Any reason you don't recommend cross sanding?
I didn't see it mentioned, but people use GOOD QUALITY PAPER. If you use some herky jerky stuff that has uneven grit on the paper you'll end up with pigtails or striations/tracers from sanding! Uni-grit as mentioned above should not cause these problems.


Modified by Grey Mouser at 4:04 PM 7-18-2008
 

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Re: DIY - Wet Sanding Basics (DesiDub)

Quote, originally posted by DesiDub »
Great write-up. Easy to follow.
I'll be using a PC 7424 and my highest cutting pad is a yellow. Most abrasive compound I have is Optimum compound. From experience, would this combination be aggressive enough to buff out the wetsanding marks?
Also, when you are done wetsanding and buffing out the scratches, do you top the area with anything additional/unusual or simply carry on with your detail as normal?
Thanks,
Kev

I think OC will take out 2K and HIGHER grit marks. So don't end your process with anything lower than 2000 grit.
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Re: DIY - Wet Sanding Basics (Grey Mouser)

I forgot one very simple and stupid question.
Are you using touch-up paint to pre-fill the scratched area and then wetsanding once it has dried to make it level?
Kev
 

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Re: DIY - Wet Sanding Basics (DesiDub)

That's a logical start, although you don't necessarily need to, many people wetsand to get rid of "orange peel" paint.
I've got some scratches from awesome people in parking lots and a few dings from "non-liable" truck drivers. Same process for both. Fill with paint, let cure, sand even, polish.
I REALLY like waiting for the paint to cure quite a while, if possible. In the area of weeks, for touch up paint to dry, and a few days between layering.
Through this process you'd be amazed at what you can restore and recover.
 

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Discussion Starter · #7 ·
Re: DIY - Wet Sanding Basics (PDong)

Quote, originally posted by DesiDub »
I'll be using a PC 7424 and my highest cutting pad is a yellow. Most abrasive compound I have is Optimum compound. From experience, would this combination be aggressive enough to buff out the wetsanding marks?
Also, when you are done wetsanding and buffing out the scratches, do you top the area with anything additional/unusual or simply carry on with your detail as normal?
Kev
You might possibly be able to get wetsading scratches out with a yellow pad and Optimum Compound. Depend on the paint hardness.
A couple of things to help accomplish this, though... 1) I wouldn't drop below 3000 grit paper. 2) Make sure to use a 4" spot buff pad on speed 6.
You will need to work that are for a good while. Make sure to wipe the area with 50/50 isopropel alcohol/water to make 100% sure that you have actually buffed the area out and that oil isn't filling the wetsanding scratches.
Once you are done buffing the area out, you simply go on with your usual detail. Nothing special required.
Quote, originally posted by Grey Mouser »
Nice write up. Any reason you don't recommend cross sanding?
I didn't see it mentioned, but people use GOOD QUALITY PAPER. If you use some herky jerky stuff that has uneven grit on the paper you'll end up with pigtails or striations/tracers from sanding! Uni-grit as mentioned above should not cause these problems.
You will find it easier to remove the wetsanding scratches if you sand in one direction and not cross sand. It will also help you better avoid those tracers you mentioned above.
Check the third paragraph from the top. Although it is a great idea to use something like Meguiar's Uni-grit, it just ins't feasable for some people to get it. And I'm not aware of any other locally sold unigrit paper in my area. So, it can be done without it, but yes, it would be better to use it if you can get it.
Quote, originally posted by Grey Mouser »
I think OC will take out 2K and HIGHER grit marks. So don't end your process with anything lower than 2000 grit.
http://****************.com/smile/emthup.gif
With a rotary. The PC will not generate as much heat. I would recommend not dropping below 3000 grit if you only have OC and a yellow pad.
Quote, originally posted by DesiDub »
I forgot one very simple and stupid question.
Are you using touch-up paint to pre-fill the scratched area and then wetsanding once it has dried to make it level?
Kev
Depends. If the scratch can not be picked with your finger nail, it is safe to wetsand it without adding touch up paint. However, if you can catch it with your finger nail,, it is best to fill the scratch with touch-up and then completed the wetsanding process. It is the same either way.
Quote, originally posted by DesiDub »
I REALLY like waiting for the paint to cure quite a while, if possible. In the area of weeks, for touch up paint to dry, and a few days between layering.
Yeah, it is good to wait at least a day for the touch-up paint to dry before you go wetsanding it. Although, I have done it a couple of hours after.


Modified by 67Customs at 12:07 PM 7-19-2008
 

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Re: DIY - Wet Sanding Basics (67Customs)

Quote, originally posted by 67Customs »

You will find it easier to remove the wetsanding scratches if you sand in one direction and not cross sand. It will also help you better avoid those tracers you mentioned above.

Cross sanding is in theory supposed to provide you with a more uniform surface after the fact. Have you ever sanded in straight lines and noticed the clear looks like it has a dip in it now? Even with a sanding block?
I was asking because everyone has their own personal preference.
 

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Discussion Starter · #9 ·
Re: DIY - Wet Sanding Basics (Grey Mouser)

Quote, originally posted by Grey Mouser »
Cross sanding is in theory supposed to provide you with a more uniform surface after the fact. Have you ever sanded in straight lines and noticed the clear looks like it has a dip in it now? Even with a sanding block?
I was asking because everyone has their own personal preference.
I haven't heard that theory nor has that been my experience. I have tried other ways, but back and forth just provides beter results for me.
I have always sanded in one direction. I do move the paper up and down the area I am sanding, but I am still moving it in that main back and forth motion I started with. So, I am not staying in one single spot. I have never had the paint dip in on me.
And to be honest, you would have to sand in one spot and take quite a bit of clear off to make a dip visible. You shouldn't be doing that much sanding in one area.
Yeah, it is personal preference. You can sand however you like. I am just saying that it is my experience that sanding in one directions makes it easier to remove the wetsanding marks during the polishing session.
 

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May I please reiterate one thing of extreme/utter importance when wet-sanding...
Use a block and SAND EVENLY.
No, your fingers cannot sand evenly. Yes, I've been caught in this line of thinking and have messed things up by learning the hard way. Please Please use a block with the paper or something like Meguiar's Unigrit blocks.
Wet sanding seems extremely straight forward and is for the most part. However, it is very easy to get too comfortable too quickly and sand through some clear around an edge or something of the sort.
 

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Re: (FliGi7)

I was trying to wet sand the back of my Jetta, where the "GLX" badge used to be. It looks like i got most of it off and its very soft, but not shiney like it used to be, looks hazy actually. Do i just need to use an orbital now with some cutting compounds?
 

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Discussion Starter · #12 ·
Re: (backheld)

Quote, originally posted by backheld »
Do i just need to use an orbital now with some cutting compounds?
That would be a good start. You might need something stronger, though.
Since I get the slight hint that you didn't read my whole post, I'll post the parts that partain to your situation and bold the most important parts...
Quote, originally posted by 67Customs »
...
Before you wet sand, you have to make sure that you have the right tools. If you don’t, you are going to be extremely disappointed in the outcome and you will probably end up making an appointment at a body shop. These are the basics…
Sandpaper (water safe)
Sanding block (will explain later)
Bucket of water
Running water (optional)
Dish Soap (optional)
Machine Buffer
Appropriate Pads
Appropriate Polishes

...
Once you have sanded until you feel satisfied, you are ready to buff out the sanding marks.
This is where my sanding pretty much DIY ends. You need to be somewhat skilled in using a buffer in order to perform the next step.
Some people ask if sanding marks are removable by hand. Well, I hope you have the endurance of a pig making love. (Google that.lol) It will take you forever to buff out sanding marks by hand and you will never get the results you want. If you don’t have a machine buffer of some sort, don’t even try to wet sand.
Other people ask if using a Dual Action polisher (orbital in your case) is enough. If you used 3000 grit and you have a cutting pad, the appropriate polish and some time, you can do it. I have buffed out 2500 grit marks with a PC before, but I had to keep going over the area. The PC 7424 is the only DA I have seen that has enough power to remove wet sanding scratches.
A rotary buffer, cutting or wool pad and the appropriate polish are needed to effectively remove the sanding scratches. You can tell if a polish is appropriate or not because it should say “Will remove 2000 or finer sanding marks.” or something similar to that.


If you are talking about a regular ol' $10-$20 orbital buffer from Wal-Mart of Advance Auto, then you will never be able to make the paint look perfect again. It will look slightly better, but not perfect.


Modified by 67Customs at 12:47 PM 12-29-2008
 

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Re: (67Customs)

oh dont be so hasty, i did read the whole thing but most of the time i polish my cars by hand because i dont want to burn the paint with the polisher. I did find another thread with which compounds to use with the orbital, even though i'm using a rotary polisher.
 

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Discussion Starter · #14 ·
Re: (backheld)

Quote, originally posted by backheld »
oh dont be so hasty, i did read the whole thing but most of the time i polish my cars by hand because i dont want to burn the paint with the polisher. I did find another thread with which compounds to use with the orbital, even though i'm using a rotary polisher.
Sorry. Most people come in her asking questions while the answer is right in front of them. I stereotyped you.

Try the orbital first, but you will probably end up using the rotary. Good luck. http://****************.com/smile/emthup.gif
 
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