Wet Sanding: What did I do wrong?

[EXTJosh]

Hey guys, first time in a long time posting. Today was my first attempt wet sanding an entire car AND using a rotary--and I've clearly missed a step somewhere. This car has returned from the body shop full of sanding scratches, so it is up to me to get rid of them. The below pictures are from my test panel on the hood. This car is a re-spray so paint readings were high (11+ mil levels) and in doing all my steps below, I have lost about 2 microns (average about 9 mils now).

Here were my steps:

- Waterless wash using Pinnacle Liquid Crystal waterless.
- Clayed with a fine grade clay bar.
Here's where things got tricky early on!...
- DA damp-sanded with 3000 then 5000 grit.
- Used a wool pad with M105 and DeWalt DWP849X. Because this was my first experience using a rotary, I began at 600 RPMs for 3 section passes and inevitably bumped up to 1400 RPMs because I was not seeing very good results at each attempt (600, 1000, 1400 RPMs).
- A lot of scratches were still left in the paint. I decided to see what the polish step could do in terms of getting out what I figured were the rotary swirls, and went to my Flex3401, M105 and a white polishing pad.
- After this step the paint was FAR from being corrected--swirls and scratches galore.
It was my thought at that point the 3000 didn't get out all the scratches, so I then repeated the same correction process above, but this time I DA damp sanded with 1500 grit (then went 3000, 5000). I was getting the same results on my wool pad from the first attempt, so I switched to a foam orange cutting pad with the rotary...swirls and scratches remained. Finished with M205 on the Flex and I got practically the SAME results.

Below pics are the end results after going through ALL the steps above (and thorough forum reading prior to starting my work). I am very disappointed with my results and can't figure out what's gone wrong. I've done small wet sanding in the past but with zero issue finishing out the paint. My thoughts are the error either lies in my DA sanding steps or in the rotary step. What're your guys' thoughts? I appreciate the help and the feedback!








- Josh

[EXTJosh]

I realize the pictures didn't come out that great after uploading. I can post clearer pics tomorrow if that helps. Thanks again guys!

[lawrenceSA]

I suspect your jump from 1500 to 3000 was the issue, in that the 3000 never pulled out all the 1500 sanding marks.

It is really important to ensure you adequately remove the previous steps sanding marks before moving on to the next step.

[GSKR]

Hey guys, first time in a long time posting. Today was my first attempt wet sanding an entire car AND using a rotary--and I've clearly missed a step somewhere. This car has returned from the body shop full of sanding scratches, so it is up to me to get rid of them. The below pictures are from my test panel on the hood. This car is a re-spray so paint readings were high (11+ mil levels) and in doing all my steps below, I have lost about 2 microns (average about 9 mils now).

Here were my steps:

- Waterless wash using Pinnacle Liquid Crystal waterless.
- Clayed with a fine grade clay bar.
Here's where things got tricky early on!...
- DA damp-sanded with 3000 then 5000 grit.
- Used a wool pad with M105 and DeWalt DWP849X. Because this was my first experience using a rotary, I began at 600 RPMs for 3 section passes and inevitably bumped up to 1400 RPMs because I was not seeing very good results at each attempt (600, 1000, 1400 RPMs).
- A lot of scratches were still left in the paint. I decided to see what the polish step could do in terms of getting out what I figured were the rotary swirls, and went to my Flex3401, M105 and a white polishing pad.
- After this step the paint was FAR from being corrected--swirls and scratches galore.
It was my thought at that point the 3000 didn't get out all the scratches, so I then repeated the same correction process above, but this time I DA damp sanded with 1500 grit (then went 3000, 5000). I was getting the same results on my wool pad from the first attempt, so I switched to a foam orange cutting pad with the rotary...swirls and scratches remained. Finished with M205 on the Flex and I got practically the SAME results.

Below pics are the end results after going through ALL the steps above (and thorough forum reading prior to starting my work). I am very disappointed with my results and can't figure out what's gone wrong. I've done small wet sanding in the past but with zero issue finishing out the paint. My thoughts are the error either lies in my DA sanding steps or in the rotary step. What're your guys' thoughts? I appreciate the help and the feedback!








- Josh

I still see deep rids.But the paint around them look clear. Hard to give advice especially wetsanding so Im going to stay out sorry.keep practicing the rotary the overall job is not perfect but I've seen worse from pro at a bodyshop.From what you described all the damage its not terrible just keep at it.

[RPM_BR]

Nobody is chiming in, I'll see if I can help you.
First, you have to be sure if the clearcoat is completely cured; press your nail in the border of the piece and see if it leaves nail mark.
Second, when I wetsand with 1500 grit, I do it by hand, and only in one direction.
Third, what LawrenceSA said.
Fourth, a good quality wool pad must be used, no twisted ply since it leaves lots of marks, and the polishing cycles must be short (because of the debris build up working backwards) and a thoroughly pad cleaning step.
Fifth, I would add an intermediate step after the wool with 105 and before the 205, if the clearcoat is on the hard side the 205 will be 'weak' to remove the wool and 105. I would add something like Menzerna 1500 (2400 new scale) or any true medium cut compound you have it with medium to hard foam on a 3401 or Rupes 21. Or even microfiber pad, to trade the remaining swirls for mf haze. But it would depend on the spot test.
If it were me, I would go with menz 300 with wool after sanding, short cycle, to level it out, and then 400 with hard foam or medium wool, and then medium cut compound with DA and, if needed, soft cut compound on DA with soft to medium foam.
I hope it helped.
Best regards

[dlc95]

It actually looks like a lot of the sanding marks have been removed, and what's left are swirls; also some pig tails - at least in the first picture. The pig tails are a result of d/a sanding. Those could also be aggressive wool pad marks.

When sanding it's best to work as clean as possible. Tracers from hand sanding, and pig tails from d/a are very easy to instill from either a build up of debris, and dirt particulates.

I also agree with what Lawrence said about needing a step between 1500 and 2000 grit.

When finishing down with fine 3000, or 5000 grit papers/discs most random orbital, and dual action tools can effectively remove them in a timely manner. If you have a Porter Cable 7424xp, or a Rupes Bigfoot tool, try M105 on a microfiber cutting disc.

If you haven't already, check this mini series of videos out.

https://m.youtube.com/watch?v=BgCmrGMhvss

[Eric@CherryOnTop]

From your process description, it looks like you did everything right: 3000-->5000-->105 with wool (and your rotary speeds seems very reasonable...

If this is fresh paint then I think your last step was too aggressive. M205 tends to mar for me on softer paint and fresh paint is soft paint. I would try some Menzerna 4000 or 4500 on a white or black pad.

Sometimes we get fooled into thinking we aren't being aggressive enough when in fact we are being overly aggressive. It's worth a shot, you can't make it worse by going less aggressive.

I really think the problem here is a m205, I've seen that type of result before with 205 on soft black paint. Changing my polish and pad fixed it. Also, if you have a non-forced DA you might get a better finished result.


Sent from my iPad using Tapatalk

[Mike Phillips]

If this is fresh paint then I think your last step was too aggressive. M205 tends to mar for me on softer paint and fresh paint is soft paint. I would try some Menzerna 4000 or 4500 on a white or black pad.

I agree with what Eric wrote.


When I look at the pictures, I'm not seeing sanding marks, I'm see light swirl or holograms left by your pad, the M205 and the rotary buffer.


Switch to a different finishing polish and if possible, get ANY orbital polisher to finish out instead of trying to finish out with the rotary.


Do you have any other polishes besides M205?


Seems it was just yesterday I was helping another guy having finishing problems with M205. It works great on harder paints but tends to micro-mar on softer paints and while there's a boatload of detailing gurus out there that will help you dial in your technique till the sun goes down it's faster, easier and simpler to simply get a different polish. And this is coming from a guy that was personally handed a laboratory made bottle of M205 from the head chemist at Meguiar's to test out before it went it to production.

[EXTJosh]

Thank you everyone for the immediate responses!

I suspect your jump from 1500 to 3000 was the issue, in that the 3000 never pulled out all the 1500 sanding marks.

It is really important to ensure you adequately remove the previous steps sanding marks before moving on to the next step.

Thank you Lawrence. I was afraid of that as well. It's like Mike says about machine work, you hear the machine kick in and your first instinct is to move it around rapidly because you know you're taking off layers of paint and intrinsically/instinctively don't want to burn through/damage the paint (he referenced polishers but to me I was doing the same with the DA sander)! I think in the case of my DA damp-sanding, I wasn't as thorough as if I had done it by hand and maybe need to slow my arm speed down a touch.

I still see deep rids.But the paint around them look clear. Hard to give advice especially wetsanding so Im going to stay out sorry.keep practicing the rotary the overall job is not perfect but I've seen worse from pro at a bodyshop.From what you described all the damage its not terrible just keep at it.

Thank you for your input and reassurance, definitely not giving up!

Nobody is chiming in, I'll see if I can help you.
First, you have to be sure if the clearcoat is completely cured; press your nail in the border of the piece and see if it leaves nail mark.
Second, when I wetsand with 1500 grit, I do it by hand, and only in one direction.
Third, what LawrenceSA said.
Fourth, a good quality wool pad must be used, no twisted ply since it leaves lots of marks, and the polishing cycles must be short (because of the debris build up working backwards) and a thoroughly pad cleaning step.
Fifth, I would add an intermediate step after the wool with 105 and before the 205, if the clearcoat is on the hard side the 205 will be 'weak' to remove the wool and 105. I would add something like Menzerna 1500 (2400 new scale) or any true medium cut compound you have it with medium to hard foam on a 3401 or Rupes 21. Or even microfiber pad, to trade the remaining swirls for mf haze. But it would depend on the spot test.
If it were me, I would go with menz 300 with wool after sanding, short cycle, to level it out, and then 400 with hard foam or medium wool, and then medium cut compound with DA and, if needed, soft cut compound on DA with soft to medium foam.
I hope it helped.
Best regards

Thank you for chiming in from Brazil! I suspected the wool pad's ability to leave a decent finish as well. I got it from a local body shop supply retailer. My first thought at seeing all those RIDS/swirls was that it was from the wool pad (and maybe not a quality one..?). I will try the intermediate step with the medium cut compound.

It actually looks like a lot of the sanding marks have been removed, and what's left are swirls; also some pig tails - at least in the first picture. The pig tails are a result of d/a sanding. Those could also be aggressive wool pad marks.

When sanding it's best to work as clean as possible. Tracers from hand sanding, and pig tails from d/a are very easy to instill from either a build up of debris, and dirt particulates.

I also agree with what Lawrence said about needing a step between 1500 and 2000 grit.

When finishing down with fine 3000, or 5000 grit papers/discs most random orbital, and dual action tools can effectively remove them in a timely manner. If you have a Porter Cable 7424xp, or a Rupes Bigfoot tool, try M105 on a microfiber cutting disc.

If you haven't already, check this mini series of videos out.

https://m.youtube.com/watch?v=BgCmrGMhvss

Good eye on the pig tails--yes that's exactly what you're seeing. They happened during the second attempt at the 1500 grit level. I was hoping the following steps would've gotten them out. The DeWalt looked like it got most of the sanding scratches out, just instilled swirls through the process. Yes, I have a PC & microfiber pads. Will have to give that a try. Will take a second look at Larry's video, thanks for the link and thank you for your input.

From your process description, it looks like you did everything right: 3000-->5000-->105 with wool (and your rotary speeds seems very reasonable...

If this is fresh paint then I think your last step was too aggressive. M205 tends to mar for me on softer paint and fresh paint is soft paint. I would try some Menzerna 4000 or 4500 on a white or black pad.

Sometimes we get fooled into thinking we aren't being aggressive enough when in fact we are being overly aggressive. It's worth a shot, you can't make it worse by going less aggressive.

I really think the problem here is a m205, I've seen that type of result before with 205 on soft black paint. Changing my polish and pad fixed it. Also, if you have a non-forced DA you might get a better finished result.


Sent from my iPad using Tapatalk

Thank you, Eric...and thank you for confirming/approving my approach--I was going crazy last night wondering if I missed a step, if my rotary speeds were off, etc.! I've got both Menz 4000 & 4500. Will try these. Going to have to see what the Flex can do as my PC is not at the shop today. Will head home if the Flex doesn't come through and dust off the PC.

I will keep you guys posted, thanks again for your help!

[EXTJosh]

I agree with what Eric wrote.


When I look at the pictures, I'm not seeing sanding marks, I'm see light swirl or holograms left by your pad, the M205 and the rotary buffer.


Switch to a different finishing polish and if possible, get ANY orbital polisher to finish out instead of trying to finish out with the rotary.


Do you have any other polishes besides M205?


Seems it was just yesterday I was helping another guy having finishing problems with M205. It works great on harder paints but tends to micro-mar on softer paints and while there's a boatload of detailing gurus out there that will help you dial in your technique till the sun goes down it's faster, easier and simpler to simply get a different polish. And this is coming from a guy that was personally handed a laboratory made bottle of M205 from the head chemist at Meguiar's to test out before it went it to production.

Mike, thank you as always for coming to my rescue and your tireless efforts to always provide help to all of us. I have the Menzerna 4000 & 4500 (what ever their new numbers are), Blackfire's gloss enhancing polish, Scholl's S30+ and Wolfgang's finishing glaze...and of course, M205. I also have a few glazes such as M305 and Jescar's finishing glaze. As you and Eric have suggested, I'm going to try the Menzerna first. Those polishes seem to always get me out of a bind when other's aren't working. Thanks again.