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

[Todd@RUPES]

Last week, in a discussion with some detailers, I theroized that the portercarble removes more paint then a rotary. My reason was simple, the rotary levels paint better and flatter, where as the isolating action of the DA could "chase the scratches" more.



So I picked up the hood of a wrecked 99 Toyato Tacoma two days ago from a local bodyshop and set to work. Unfortunately, my camera is down (in the shop for sensor cleaning) so I couldn`t take pictures, but I will redo this test with pictures in the near future.



The hood was black and had moderate to light swirling (and hologramming) but a lot of rids in straight lines. Perfect for the test, IMO.



I taped the hood into the thirds, then using thin tape, divided each third into the thirds (so I had a tic-tac-toe board). By marking and using a straight edge, I was able to accurately measure the same exact spots to ensure accurate paint differences.



Here is a picture showing what I did.



The hood was orginally taped front to back to split it in the sections. The passenger side was to get wetsanding then polished to perfection. The middle section was to get polished only with a rotary to perfection. And the driverside was to get only the DA until perfection.



To make measuring the paint more accurate, I divided the box horziontally (thin green lines) and marked the tape using black marker (black dots on green lines). This allowed me to use a straightedge to measure the same area each time (orangish dots).



I also numbered the panels vertically, with sections 1-3 getting wetsanded, 4-6 getting machined with a rotary, and 7-9 using the portercable.







First up was the DA only side. To keep this test fair, I elected to use commonly (and similar products) for all three sides. Since Menzerna SIP and 106ff have such a following by both rotary and PC users, I decieded on these two for the work. I also included PowerGloss Compound for rotary use, since one of the benefits of the rotary is the ability to level paint quicker.



On the DA, I used a 6 inch Lake Country Orange CCS pad for the "cutting" and a couple drops of Menzerna SIP. I polished using slow arm speed and long overlapping passes in both left-right-left and up-down-up motions until the polish began to clear and flash. This process took about 3 minutes to fully break the polish down per application.



After one application, I wiped clean (I kept 91 percent alcohol and fresh microfibers near by for quick removal of product). There was a nice reduction in the swirls and holograms, though some deeper swirls remained, as well as moderate rids.



Time for another application...



and another...



and another...



Finally after polishing each section driver side hood 5 times, I had removed all swirls, but still had some straight line rids. So I continued on...

For 3 more passes, until all defects where removed and the paint was perfect. To do the entire passenger side of the hood to this point had taken slightly over an hour. Next I followed with 106ff to remove any micromarring on speed 5 and a Lake Country White CCS 6 inch pad.



The paint looked great.



Next up was the center section, with rotary only. Because one of the advantages of the rotary is the ability to use more aggressive methods, I did keep a Lake Country Yellow Pad and Menenzerna PowerGloss on hand. But to keep the test fair, I wanted to start with SIP and an orange pad (same as Porter Cable).



I worked the SIP by staring at 1000 rpm, then jumping up to 1700 before cascading back down to 1000 rpm. It took about 40 seconds per application. One pass reduced all the haze and swirl in the paint, but still left the rids, which looked untouched. I decieded to step up to PowerGloss and the Yellow Pad. I kept the RPM at 1500 and worked the PowerGloss until clear, about 20 seconds each application.



After one application in the center of the hood, I wiped clean with alochol. 90 percent of the rids where gone, but there was moderate hologramming from the yellow pad and compound. I required one more pass of PowerGloss (at 1200 rpm and worked slightly longer) for complete removal. I followed with with Menzerna SIP and an orange pad which made the paint perfect. I finished with 106ff on a blue pad.



Now 2/3rds of the paint where perfect. Where as the DA side took an hour to get perfect (and 8 application of SIP/1 of 106ff), the rotary side moved quickly 15 minutes (2 applications of PG and Yellow, 1 application of SIP and Orange, 1 application of 106ff and blue).





Now for the wesanding. I used Meguiars Unigrit sandpaper (3000 grit) for the defect removal. I started by soaking the paper in a bucket with a couple drops of dawn for 15 minutes, then wrapped the paper around a soft flexiable Meguiars sanding block. Car was used to remove just enough paint to level the rids.



I would make three or four passes with the 3000 grit in one direction then wipe clean and dry and inspect. The paint was gray, but the rids where still visible. This was followed by three to four more passes and reinspected until all visible RIDS where removed.



After 3000 grit (it took only 5-8 "passes" to remove all rids) the paint had a nice, level satin finish.



Now it was time to polish the paint. 3000 grit wet leaves an incrediably nice finish, the doesn`t always require a compound to cut it so I started with SIP and an Orange pad worked at 1700 rpm. It restored full gloss to the paint very quickly, and showed no sanding marks that would need to be cut. I finished with one application of 106ff on a blue pad to ensure paint perfection.



So now the hood had been made perfect by all three standards, and to my eyes looked perfect.



So what was my final verdict?



Here are the measured paint levels before and after and my conclusion.



Up first, sections 1-3, the wetsanded side.



Before After Reduction

1. 3.8mil 3.8mil .0mil

2. 4.1mil 4.0mil .1mil

3. 4.0mil 3.9mil .1mil



11.9mil 11.7.m .2mil



So the wetsanded and polished side showed a total of average of .67mil reduction or a total of .2mils for three sections.



Second, section 4-6, the rotary side. Compounded, polished, finished.



Before After Reduction

4. 4.1mil 4.0mil .1mil

5. 4.2mil 4.0mil .2mil

6 4.2mil 4.1mil .1mil



12.5mil 12.1mil .4mil



The rotary side showed an average of .13 mil reduction or a total of .4 mils over 3 sections.



Lastly the PC



Before After Reduction

7. 3.8mil 3.6mil .2mil

8. 4.3mil 4.2mil .1mil

9. 4.2mil 4.0mil .2mil



12.3mil 11.8mil .5mil



The PC side showed the most reduction at .167mil reduction average or .5 mils in three sections.



An intresting conclusion, but it no ways meant to be an end all, be all. I thought the conclusion was pretty cool, so I thought I would share.

[imported_Detailing Technology]

Good topic. Info any body man will agree with you on. Use a D/A to remove an excess of material.



If you need help to get thsoe results into tables, let me know, they would be easier to read.

[SuperBee364]

Very interesting and well done, Todd. Hard to argue with those results, surprising as they are. Look forward to the pics!

[20jettatdi03]

So the wetsanded and polished side showed a total of average of .67mil reduction or a total of .2mils for three sections.

I think you meant .067mil reduction

Thanks alot for the info, interesting results

[imported_Dave1]

Good topic. Info any body man will agree with you on. Use a D/A to remove an excess of material.

I`ve never heard that a PC will remove more defects than a rotary before......



Thanks for the study Todd......:xyxthumbs



Very interesting findings to say the least.

[jpochile]

Hi Todd :





WOW what a surprise . Thanks for a very interesting study . The results are incredible .



Cheers , Jean Paul

[Driven Auto Detail]

Very cool test Todd. I never would have guessed that the PC removed more clear. Thanks for going out of your way to post your findings! This thread deserves a sticky!

[imported_Detailing Technology]

I`ve never heard that a PC will remove more defects than a rotary before......



Thanks for the study Todd......:xyxthumbs



Very interesting findings to say the least.

It takes more time. Like hours more....

[Todd@RUPES]

When we are removing RIDS, we are releveling the paint to the point of the lowest section of the scratch. How we get there is completely up to us, but the point is that the paint needs to be removed.



While the results where intresting (and this one test could be picked apart by so many variables that it isn`t even close to a great study, just an observation) I think they make sense.



With wetsanding, we have the ablility to gauge are performance very accurately. There are no abrasives to diminish, you simply remove clearcoat (very flattley with out chasing the scratches downward), check, and continue. You can be very precise.



With a rotary, you have more precision (like a katana) then a Porter Cable (a unwieldly broadsword). Also, I would tend to think that motion of the D/A would "chase" the defects down deeper.



Of course I could have wetsanded first with 1200 grit, or polished with M105 and a wool, and completely changed the results.



I think that in the right hands (given that the same total amount of paint has to be removed regardless of the method used) a rotary offers more precision then a porter cable and that wetsanding offers the ultimate in precision (if used correctly).



Maybe I`m wrong, but should make a for a good discussion!

[HybridKOOP]

Great test, thanks much for sharing.



Would you usually use a rotary on an average car in "good shape" with minor swirls from improper washing? I have a Dewalt 849 and a PC as well. Just scooped up an `04 white Honda S2000 and am contemplating what road to take. At first I was totally against the Dewalt for the job, but now I am thinking outside of the box!

[jordanrossbell]

Well done sir, this was definitely not what i expected. Makes the rotary look even better, less paint removed and way faster.

[Carbon Blue]

very interesting. Hey Todd do you think you can explain what you mean when you say that the PC "chases" into the scratch? I guess what im trying to say is that im having a hard time understanding how the rotary can remove less paint at a faster rate to achieve RIDS removal? I would just think that the amount of paint removed would be equal among the 3 (rotary, DA, wetsanding) if the RIDS were all the same depth.

[2KLS1]

I have the same question as CarbonBlue. What do you mean by "chasing" scratches? Regardless of what machine you use, you still have to get to the bottom of the scratch correct?

[Glossy McGlosserton]

This is the sort of discussion that keeps me interested in Autopia. Very cool.



I have never thought of "precision" as limiting the clear removed. Like CarbonBlue, I would have thought that a scratch is a scratch, and the amount of clear to be removed to eliminate the scratch would be the same, by any method.



But even though that is true for any one scratch, the OVERALL amount of clear removed is lessened by using a tool that can be controlled more precisely to remove clear only where it needs to be removed. In other words, areas without deeper scratches keep their clear more easily when a more precise tool is used to hone in on the repair.



(Another option is to settle for less than absolute perfection. That saves a lot of clear.)



Thanks for doing this!

[evilWagon]

Hmm, so wetsanding and then polishing is the way to go?



I wonder why that is?