Tips on WetSanding

G

Grabby

New member
All right to all the detailing vets here on Autopia. I need your help and I need it big time.



I just wet sanded a very small part on my car using a 2000 grit 3M sandpaper. I soaked it for about twenty minutes. After polishing the part, all the sanding marks were removed except this part where discoloration had occurred. My car is silver and the discoloration is dark silver.

I used a 1"x1/2" eraser as my backing pad. I only used that much of sand paper as well.



I tried polishing it out to no avail. I think I went through the clear coat. Am I right?



If so, how do I avoid this the next time and do you have any tips for me?



Thanks.



Grabby
 
I have a practice trunk that I did the same thing on. I realized I was sanding too much in one spot, when wet sanding make less passes in the same area. Also what I learned from working on my trunk is to watch out for high spots, I made those same marks where the trunk curved away toward the seam.



btw, I've heard that it helps to soak the paper over night. I too only soaked mine for 30 or so min, not sure what that might have had on the effects though.



Good luck! Get yourself some practice parts! :bigups
 
I used a 1"x1/2" eraser as my backing pad. I only used that much of sand paper as well.



Not sure what you mean.



It sounds like you did go through, paint color change, not much you can do. Next time watch your progress with the wet sanding. Most cars have enough orange peel to see the transition into deeper clear. Meaning, when you sand and then see the sanding marks are all unison, no hills and valleys, time to stop.



I have oversanded on purpose a few times and then compounded and then polished out, it did not remove enough clear to cause anymore damage.
 
It also has very little to do with how long you soak the paper. You went through! It could have happened when sanding or when compounding.



So don't think another 10 minutes of soaking the 2000 could have saved you.
 
I've sanded with dry paper and a spray bottle, on occasion, cuts a little more but not extreme.
 
Curses.



Oh well. Is there a pattern that I should follow? Like do I polish in an orbital manner or back and forth? How much pressure and do I have to keep on spray water every second or a spritz for every two or three passes would do?



I went through a part that I wet sanded without removing the clear. I polished it with a Yellow Lake Country Pad and 3M's Super Duty Rubbing Compound. It removed the haze but I still notice deep sanding marks. Should I resort to wool?



By the way, what's the least aggressive way to remove 2000 grit sanding marks?



Thanks,



Grabby
 
Grabby said:
Curses.



Oh well. Is there a pattern that I should follow? Like do I polish in an orbital manner or back and forth? How much pressure and do I have to keep on spray water every second or a spritz for every two or three passes would do?



I went through a part that I wet sanded without removing the clear. I polished it with a Yellow Lake Country Pad and 3M's Super Duty Rubbing Compound. It removed the haze but I still notice deep sanding marks. Should I resort to wool?



By the way, what's the least aggressive way to remove 2000 grit sanding marks?



Thanks,



Grabby
Click to expand...



I sand in a uniform pattern. Back and forth, so I have uniform sanding marks to remove. I also sand so that the surface is a solid white, not spotty, where I wanted to remove the defect.

Spray bottle, up to you, I never have used one. I just keep the panel wet with water from the bucket (very little soap) and squeege to check progress.



2000 marks will come out with foam or wool. Are you using a rotary?
 
Yep. Makita 9227c with 6.5" Lake Country Buffing pads. I ran it at about 1500 rpm. Maybe I applied to much pressure that's why the sanding marks are deeper?
 
Wet Sanding or Buffing?



Wetsanding about 25-30 passes.



Buffing it off, put some product, spread, at 1500 rpm 5 passes for around 3 times.
 
try about 5 passes, then squeegie all the water off the area and inspect closely through the dry haze to see if you have removed whatever defect you were trying to get out. 20-30 passes could take all the clear off one area. Its very hard to see when the area is wet because it conceals the defect in the shine of the water. It may look like you did not do anything because of this and therefore you keep sanding. Take just a few passes and then dry the area before sanding anymore. That usually keeps me on the safe side. I also use wool to remove sand scratches mainly because it takes so little time and much less heat.
 
It ultimately depends on what you are wet sanding for, but ~5 back and forth passes (in 1 spot) should be plenty in most cases (for defect removal) using light to medium pressure. On larger areas that I do via sanding block, I prefer to use a cross-hatch pattern which allows for easier removal of sanding marks (when buffing) and more uniform leveling of the surface.
 
When you are wet sanding I really think you need a paint thickness gauge. If you don't have any idea how much clear is on this certain car, you are just gambling with your job. Once you get a good idea how much clear is removed from certain types of cars, you MIGHT be able to get by without a PTG.



My .1 opinion
 
Grabby said:
Wetsanding about 25-30 passes.
Click to expand...



Um, me thinks thats what did it right there. 6-8 passes will do it, again you can always keep under doing it, you can only over due it once.



*btw, there are some great wet sanding videos on youtube, do a search on "Meguiars wetsanding" its a 5 part series. Lots of good info.
 
btw, does it kinda look like this spot over on the right? If so you can see whats next once you have that spot... straight thru the paint onto primer.

TrunkAfter.jpg


Sanding different areas...

TrunkAfterAway.jpg
 
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