Wet sanding, cutting and buffing with only a DA

RaskyR1

RaskyR1

Rasky's Auto Detailing
Admittedly I can be a little old school at times, and wet sanding is probably one of those areas. With all the recent threads on wet sanding a fellow detailer, one I respect, David Fermani, mentioned to me how he felt the sanding scratch removal was more efficient by DA as it reduced the number of buffing steps needed (3000+ girt sanding). I've been removing sanding scratches via rotary polisher for over 20 years now and being a little old school like I am I found this hard to believe, but I am always willing to learn new things and figured I'd give it a try.





Since some jerk (aka. bad word) decided it would be fun to slam his door into the side of my car last weekend (even though I was parked out back next to a curb) I had a good test car for Davids method. Luckily it didn't dent my door but car was pretty dirty at the time and as you can see it left some nice deep scuff marks, which measured 3-4 inches vertically. I'm confident I could have removed them using only M105, but this gave me a good reason to wet sand the area and then try removing the sanding marks by DA.







Here is are some pics of the scuff

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PTG readings on the door averaged around 115 microns. Since this is car still has the original factory paint, and having know my paint was pretty thin from the factory, I wanted to be sure I didn't remove too much clear.

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I first sanded with Mirka Abralon 2000 grit disks on the PCXP using a speed of 3.5

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I then followed that up with some Abralon 4000 grit disks....you can see a noticeable difference in the two in how much more dull the 2000 grit looked.

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I then primed an orange LC pad with M105 and made 1 section pass (3 vertical, 3 horizontal over lapping passes) using the KBM on the PCXP, speed 6.



Here is how the paint looked after that pass!

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Pigment transfer from my tinted clear...

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After a quick section pass with M205 on a black LC pad here were the results.

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I must say I was very impressed at how quickly this method was able to remove the sanding scratches. Keep in mind that the paint on my car is very soft and the results may very on different paints. I'd definitely like to try this method out on a few more paint types, but as of now it seems very promising.



Total material removal was 8-10 microns



Thanks David!





Next up will be this bad boy which has some crazy hard paint! May be a while before I get to it though.

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Rasky
 
rasky, did you use an air sander? and is that factory paint, just wondering because i've never seen a clear tinted with color unless it was for a blending coat
 
advs1 said:
i just would never use a PC to sand paint. the stroke is all wrong for it. maybe for wood yeah
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Meguiars makes a dedicated pc attachment for damp sanding and it works wonders
 
nice. i still dont think i'd feel comfortable using a PC to do wet sanding. i've only done it by hand for factory clear and with air sander with 2.5mm stroke for repaints. PC just seems like it would not be comfortable to go over anything other than flat surfaces
 
advs1 said:
rasky, did you use an air sander? and is that factory paint, just wondering because i've never seen a clear tinted with color unless it was for a blending coat
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Yep, factory paint. It's Milano Red and it, along with a handful of other cars come with a tinted clear from the factory. I'm not sure why they do it...maybe adds more depth to the paint?



Kevin Brown has some nice discussion on the larger stroke of the PC vs. an air DA in the link below.

http://www.autopia.org/forum/1328233-post12.html

After using my PC to wet sand this '68 Firebird I must say I like using the PC better than my air DA. Even with my 60gal compressor there is always a little speed fluctuation with the air sander and I like the consistent speed of the PC. The air DA is a little better for tight spots though, which Kevin mentions as well.



Don't get me wrong, I've been removing sanding scratches via rotary for 20+ years now but this little test panel has made me reconsider. It would also be nice to do a side by side comparison on a hood between the two methods. ;)





Rasky
 
RaskyR1 said:
Don't get me wrong, I've been removing sanding scratches via rotary for 20+ years now but this little test panel has made me reconsider. It would also be nice to do a side by side comparison on a hood between the two methods. ;)
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Rasky - Another great thread showing how handy a PC can be. You could literally never even need to pick up a rotary anymore. These days I'll try 105/KBM 1st to gauge the correction. If that doesn't work as needed, I'll just slap on a 3000 Trizact disk and quickly level the defects with a few quick passes. The sanding marks are so shallow that 105/KBM removes them instantly. It also makes the finish look so much clearer and flat. Not to mention alot less touch time spent doing 3-4 buffing steps.



Question: The marring on your car didn't appear to be too deep. I would have liked to see how much each step reduced the film thickness. Could you have opted to use the 4000 instead of 2000? If so, do you think the film thickness would have been evaded less? Just wondering. Again awsome job.



toyotaguy said:
yeah imagine that, rotary/flex isnt the end all...LOL
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Sure isn't! With the way new technology is advancing, the rotary may become obsolete.



advs1 said:
i just would never use a PC to sand paint. the stroke is all wrong for it. maybe for wood yeah
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The longer stroke/orbit not only removes more defects faster, but when used wet (or as 3M says "damp") it reduces pigtailes.



advs1 said:
yeah but that was a custom repaint. how about on factory clear??
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Makes no difference. Yes, a fresh repaint will respond quicker to sanding/polishing, but both can be done effectively with a PC/larger stroke. 3M also makes an interface pad that can be used for curved surfaces. It knocks down the aggressiveness of the sandpaper, but maybe by ~500 which is probably a good thing seeing that these surfaces are usually thinner.
 
David Fermani said:
Rasky - Another great thread showing how handy a PC can be. You could literally never even need to pick up a rotary anymore. These days I'll try 105/KBM 1st to gauge the correction. If that doesn't work as needed, I'll just slap on a 3000 Trizact disk and quickly level the defects with a few quick passes. The sanding marks are so shallow that 105/KBM removes them instantly. It also makes the finish look so much clearer and flat. Not to mention alot less touch time spent doing 3-4 buffing steps.



Question: The marring on your car didn't appear to be too deep. I would have liked to see how much each step reduced the film thickness. Could you have opted to use the 4000 instead of 2000? If so, do you think the film thickness would have been evaded less? Just wondering. Again awsome job.







Sure isn't! With the way new technology is advancing, the rotary may become obsolete.

i doubt that will ever happen





The longer stroke/orbit not only removes more defects faster, but when used wet (or as 3M says "damp") it reduces pigtailes.



i was always under the impression the shorter stroke produced better clarity. i'm not always concerned with speed



Makes no difference. Yes, a fresh repaint will respond quicker to sanding/polishing, but both can be done effectively with a PC/larger stroke. 3M also makes an interface pad that can be used for curved surfaces. It knocks down the aggressiveness of the sandpaper, but maybe by ~500 which is probably a good thing seeing that these surfaces are usually thinner.
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..........
 
i doubt that will ever happen
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It kinda already has started to.



i was always under the impression the shorter stroke produced better clarity.
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I've never seen or heard this before. Where did you read it?



i'm not always concerned with speed
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Yes. Not always the case for some, but 99% of the industry that uses sandpaper happens to be Body Shops which pretty much focus on speed (and ease of use).
 
David Fermani said:
Rasky -



Question: The marring on your car didn't appear to be too deep. I would have liked to see how much each step reduced the film thickness. Could you have opted to use the 4000 instead of 2000? If so, do you think the film thickness would have been evaded less? Just wondering. Again awsome job.
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Yeah, the marring was definitely not that deep. As state, I likely could have just removed it with the M105 and the PC. I only did the 2000/4000 to see how much material would be removed and no doubt it would have been less had I only used the 4000. I was out of the 3000 Trizact discs, otherwise I would have just used them. ;)





More testing to come that's for sure. :2thumbs:
 
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