Wetsanding vs. Rotary vs. PC, what removes more paint? (The answer may shock you)

Carbon Blue said:
but why wouldnt the rotary chase the scratch?
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I would think that a rotary does chase down the marring/scratches as well. But one of the advantages is the abililty to uses a more aggresive approach which should remove everything around the scratch quicker. I guess its hard to explain, but in my head (which means nothing) I would think the rotary would do less chasing because of the speed at which it removes paint.
 
Nice write up and makes perfect sense. Next time I would love to see how these new Forced Rotation ROB buffers like the Flex or Makita BO6040 fair as far as paint removal.
 
TH0001 said:
Come on down to Orlando and I'll show you how to do both.



I will also do what I did with Pats300ZX (the moderator) and prove to you that SIP and 106ff fill (ask Pat).
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I come down to orlando a few times a year. I might contact you sometime. :usa
 
I think that this also needs to be contrasted with wet sanding by machine.



This thread on DetailingWorld was really really informative on the true value of consistent wetsanding.



The findings in this thread really enlightened me. They showed that the machine wetsanding was much more precise at removing specific amounts of clear than simply compounding them out. Logically this makes a lot of sense. Sandpaper doesn't break down like polishes do, which means that across the surface they are very consistent. Polishes can break down unevenly across your work surface, meaning not only will scratches break down unevenly across that surface, but your overall clear coat level will remain uneven.



They also showed that since the sandpaper breaks down the clear very quickly, you can use multiple sanding steps up to 3-4000 grit and then a minimal amount of finish polishing in order to achieve a perfect finish. They showed that using their techniques, a vehicle in need of serious correction could be finished much more quickly, and effectively, by wet sanding and polishing than by polishing alone.



Couple that with these findings by Todd, and it makes sense that it would not only be a faster way to finish a car, but more clear coat conscious as well.
 
You also knock people out with the finished product. Road "dimples" are dramatically reduced. Scuff, abrasions, rub-off is removed or seriously lightened. The surface if the car is completely stripped and renewed, most of the time flatter then when you started.



My opinion is this demonstrator goes too close to the edges. In wet sanding over 1,500 cars, I never would go right to the edge of a panel like that. I always leave 1/4" untouched. Edges are where you burn paint 99.999% of the time. Why risk it, you will never notice the difference.



The trick is finding enough customers to pay for it. I wouldnt go through the steps without adequate compensation.
 
thanks everyone, alot of this makes more sense now and I think I can really grasp the idea of "chasing". This may be off topic but what grit sand paper do you guys recommend when sanding clearcoated body panels? how about singlestage paint? I know its all relative but would 4000 grit be too high of a grit?
 
4000 is too high. Personally the highest grit i use is 2000, though i might add a step and resand with 2500 or 3000 to see if it polishes out much faster.



If i am doing a lot of correction work, i just keep some 2000 soaking in water day after day.

Walk around the car and sand the deeper scratches and then continue with the compound/polish.

Much faster than trying to cut them out by pad.
 
Carbon Blue said:
but why wouldnt the rotary chase the scratch?
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I think the premise is that you use less pressure with the rotary, therefore the pad penetrates less into the scratch.



Nice experiment, TH0001!
 
jsatek said:
You also knock people out with the finished product. Road "dimples" are dramatically reduced. Scuff, abrasions, rub-off is removed or seriously lightened. The surface if the car is completely stripped and renewed, most of the time flatter then when you started.



My opinion is this demonstrator goes too close to the edges. In wet sanding over 1,500 cars, I never would go right to the edge of a panel like that. I always leave 1/4" untouched. Edges are where you burn paint 99.999% of the time. Why risk it, you will never notice the difference.



The trick is finding enough customers to pay for it. I wouldnt go through the steps without adequate compensation.
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Same here. I don't even bother taping it off, I just don't get that close when compounding. I do go right up to the edges with the final polish, though. Like you said, it's not often that it's even noticeable.
 
only a todd post could have 5 pages in the 2nd day! haha. Great experiment man! I have always wondered! I guess this disproves that wetsanding is (VERY) harmful to a cars paint. This makes a lot of sense! And you never cease to amaze me at how good your write ups and details of EVERYTHING is. And when are we going to see some more details from you and brian!? I wanna see some pics from THE porsche last week!



,Daniel
 
Setec Astronomy said:
I think the premise is that you use less pressure with the rotary, therefore the pad penetrates less into the scratch.
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I don't think pads penetrate scratches as much as the couplant in between the pad and the scratches......(until the bottom)



Todd's thread here is very interesting and has changed my thinking in dealing with heavier paint correction......I enjoy reading his takes and his style of work....



Scratch chasing when buffing out a hood with a polish wasn't something I considered when removing enough top clear coat before. But is is now.....



I'm going to learn some more about this with a P/B friend of mine this weekend....



The bottom of the scratch is something that I want to find out more about......(my wife is laughing at me while I post this btw....:D)
 
I agree, I don't think a foam pad penetrates a scratch-wool pads might. What penetrates and works the scratch is the compound. The dual action of a PC might work the compound into the scratch more than a singular circular motion of a rotary spinning at 1500-2200 rpm.
 
Yeah, I suspect that the pressure issue has something to do with why the PC removes more clear than the rotary when doing the same level of correction and that the PC is less efficient as it moves in a (generally) RO manner as opposed to the more directly applied force of the rotary's (merely) spinning movement.



No question in my mind about the wetsanding taking off less overall clear, my painter was telling me that before/during/after my rotarying the BMW to death trying to remove its marring (gee, shoulda listened to him :o ).



But IMO we oughta keep in mind that *any* type of serious correction takes off a lot of clear. Take off 0.1-0.2 mils a few times and you can never correct it again (at least if you plan to park it in the sun).



TH0001- I'm late to this party, but I did want to thank you for doing all of this :xyxthumbs :bow



The only thing I :think: about is the way you added up the removed clear for an aggregate "total" of each section; I wouldn't have done that as IMO what matters is (only) how much came off each *individual* section (at least to my way of thinking). But that total did make for easy comparison so please don't take my musings the wrong way.



Heh heh, the thought of you doing all that work and preparing your posts on this thread simply boggles my mind!
 
baseballlover1 said:
only a todd post could have 5 pages in the 2nd day! haha. Great experiment man! I have always wondered! I guess this disproves that wetsanding is (VERY) harmful to a cars paint. This makes a lot of sense! And you never cease to amaze me at how good your write ups and details of EVERYTHING is. And when are we going to see some more details from you and brian!? I wanna see some pics from THE porsche last week!



,Daniel
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Hey man, whats up! I don't think this disproves anything, but it does make sense (to me, atleast).



Which Porsche from last week? In the last 10 days I have detailed a Carrera GT, 2 GT2's, a 930 Turbo, a 930 Turbo Slantnose, and a '73 Carrera RS. Any one in particular?
 
Quick questions - what are RIDS? and what is PTG? I gotta admit this thread is really interesting, i like the fact that all this info sort of supports my wanting to wetsand my dads 2006 black jetta which has real nasty OP and moderate swirls. The thing is that I'm a newb and I can already picture me messing up and taking off way too much CC on the car. I would probably practice on some junk panels before I ever think of doing it on his car. Also, I'm in the process of choosing whether to buy a UDM or a PC, but it seems a UDM would be a better choice because I figure it would take a little less time to remove defects due to the 20% power increase, therefore chasing the scratches less than a PC would. Does this make any sense? Or should I just get rid of my fears and get a rotary?
 
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