Mercedes 500 Complete wetsand

[Eddie6th]

Re: Mercedes 500 Complete wetsand

very Good work..

I wouldn't bash you for not using a ptg...Your practice paid off.

[Michael Stoops]

Re: Mercedes 500 Complete wetsand

Brave indeed.

You mentioned that on the test panel you've been working on it took you a fair bit of work to sand through the clear coat. While sanding all the way through the clear is, obviously, a major problem, you don't need to get that far before setting yourself up for a major fail down the line.

Consider that a modern clear coat is only about 2 mils thick (give or take - with take being the operative word since some are not that thick) it is generally recommended to not remove more than 0.5 mils through the life of the vehicle. That generally means one session of very light sanding and rotary buffing to remove the sanding marks. That's it. You're done. For ever.

Consider Kickin Griffin's write up Paint Removal by Polishing - An Example (Rotary) where he did no wet sanding whatsoever, just multiple rotary buffing steps to remove some pretty severe defects. He started with a total film build of 119um, or roughly 4.7 mils. Keep in mind that is primer, color, and clear with clear accounting for only about 2 mils - give or take. When all was said and done, he removed 0.47 mil, which is right at the limit suggested by most auto makers, paint suppliers, etc.

Superior Shine did a similar write up a few years back - How much paint are you removing. but he wet sanded first. With 4000 grit! He then machine polished using accepted practices and in the end he had removed 0.3 mils. Close to the limit, but still safe. But that paint can not safely go through the same process again, nor could it safely go through half of what Kickin Griffin did in the aforementioned post.

The reason for this is that clear coat contains UV inhibitors, and those UV inhibitors have a tendency to migrate toward the surface as the clear dries. Not always, and not fully, but to some varying degrees. But even if these UV inhibitors remained uniformly dispersed throughout the clear coat, by removing 25% of the clear you remove 25% of the UV inhibitors. Remove 50% of the clear and you've seriously comprised the clear coat's ability to do it's job properly and you run the very real risk of premature clear coat failure. If any percentage of the UV inhibitors have migrated toward the surface while that clear was curing, you've removed far more than you might imagine.

Unless you're measuring, and not just before and after, but during the process, you have no idea how much clear you're taking off. You have no idea how seriously you may be compromising the quality and longevity of the clear. Yes, we would all love to have zero orange peel in our paint. And, yes, the worse the orange peel is the worse it looks. But the worse the orange peel is, the more you need to sand it to get rid of it. And the more you sand it......... well, you know where this is going.

Of course we aren't saying that you should never wet sand a vehicle. Wet sanding has it's uses and there are times when it may be the only way to correct an issue. But the two gentlemen who created the threads linked to above have years of experience with this process, and with the necessary buffing steps needed to complete the process - or just rotary buffing in general. Even with all their expertise, a "simple" wet sand, cut and buff process (or in Kickin Griffin's case, just buffing) took them to the limit of what really should be done. Imagine someone without that level of experience attempting this. We get phone calls to our call center from people who find themselves in much, much too deep after getting started with something they should never have attempted in the first place.

[Fischer]

Re: Mercedes 500 Complete wetsand

That's it. You're done. For ever.

Enough said there.

Ill be ordering some kind of paint gauge to see how much damage Ive done and post it up here so I can take my internet lashings.

But either way, this is going to be my dads pride and joy and not a DD, more like once a week car and put away for the winter. Oh well, ill post up results once I get my hands on a paint guage.

[Carfire]

Re: Mercedes 500 Complete wetsand

Excellent Job!!
I'm surprised the dealership didn't "buff" or do anything to the paint...I mean I know they do not do a good job there, but it looks like they did not do anything.
Looks Great!!
AMAZING Reflections!!
Keep Up the Great Work!

[Hemin8r]

Re: Mercedes 500 Complete wetsand

You can definitely see the clarity, nice job.

[fzr confused]

Re: Mercedes 500 Complete wetsand

awesome job! i wouldnt have the testicular fortitude to attempt that on anything more than my ranger LOL

[Fischer]

Re: Mercedes 500 Complete wetsand

Excellent Job!!
I'm surprised the dealership didn't "buff" or do anything to the paint...I mean I know they do not do a good job there, but it looks like they did not do anything.

They did do something. They sprayed down the engine bay with this stuff that is like WD40. Awful messy stuff. I must say the interior was in tip top shape. The leather isnt stressed, no cracks stains or anything.

The back has been repainted however because it had the obvious "shanty" orange peel.

[the_invisible]

Re: Mercedes 500 Complete wetsand

I talked to the manager of my frequent bodyshop today. I know the manager, he's from the same church I go to and I see him every week. I also talked to one of the painters that works at the bodyshop. I was asking them for advice regarding wetsanding my BMW.

Basically what they have been telling me is that it is extremely rare that 2000 grit paper will ever sand through the clear coat. 2000 grit sandpaper is designed mainly for the purpose of removing orange peel. And almost all bodyshops utilize 2000 grit sandpaper after a fresh paint job to remove orange peel. Orange peel occurs ALL THE TIME and they must be corrected somewhat to bring about satisfaction to both the customers and the industry standards set by the Insurance Company of British Columbia.

They also added that fresh clear coat are rarely reflective due to the shift in temperature between spraying and baking. Wetsanding (followed by compounding) is almost required all the time to restore reflectivity to the new paint job.

Also, they have been telling me that unless you use your thumb to rub in the same spot for literally 3 minutes using 1000 grit paper, you would never sand through the clear. Of course, frantically sanding with a 2000 grit paper would damage the clear coat as well, but a person with the courage and knowledge to wetsand a vehicle's paint must already have some common sense not to do that.

The key to safe wetsanding is the same no matter who you talk to. Sand down the peaks until they meet the valley (or trophs). Once you see the peaks disappear, that's an indication to slow down.

The painter basically laughed at me for sounding nervous about it. Of course, he warned me not to go too quickly, and use light pressure. And he also suggested that if possible, use 2000 grit to minimize the danger. The painter assured me that it will be fine. Even Franky (Shyneman123) suggests that 2000 grit is extremely safe to use on clear coat. Franky himself uses 1500 grit at the bodyshop to remove orange peel. There are sandpapers designed specifically to remove clear coat, and those are 800 and 1000 grit paper. 2000 grit is not designed to remove clear coat if used correctly.

One thing to note is that the maximum grit of sandpaper for paint jobs is 2000 grit. 2500 or higher are essentially detailing sandpaper. They only touch the very surface of the clear coat. 2500 grit or higher sandpapers are not powerful enough to quickly remove defects found on new paint jobs. They are usually used by detailers to remove light scratches or sand away touchup oversprays.

Truthfully, it's not as hard as it sounds. Many people on Autopia have done it. They started without any experience and had never damaged any cars from doing it.

I have been wetsanding different areas on my cars with some "medium grade" 3M 2000 and 2500 grit sandpaper. I am not seeing any negative effects other than that the sanded areas now have more depth and reflectivity than when it was brand spanking new.

[Michael Stoops]

Re: Mercedes 500 Complete wetsand

All of that sounds pretty much spot on, but there is a very important distinction here:

You're talking about paint from a body shop, the OP is talking about factory paint. A body shop has the luxury of not only laying down more clear with the intent of wet sanding to remove orange peel, but they know how much clear they've laid down. A factory paint job only gives you 2 mils or less of clear, but they also graciously include the orange peel. If the body shop lays down an extra mil of clear, that gives them (relatively speaking) a huge advantage and safety margin.

You'll see recommendations from auto manufacturers, even printed in the shop manuals, warning against removing more than .5 mil of clear. Even if you successfully remove only that much, you no longer have any leeway for even aggressive buffing in the future. Look again at the numbers measured by some very talented, highly respected detailers. And as mentioned previously, you don't need to "go through the clear" to run into issues later on, you only need to exceed that .5 mil threshold on a factory paint job. And you can indeed do that 2000 grit paper if you don't know what you're doing.

Go back and ask the your body shop guy if he would allow a complete novice to walk in off the street and just start wet sanding a car with no supervision, and using whatever sand paper he wanted. THAT is when things go horribly wrong, and THAT is all we're trying to caution against here. We aren't telling people that wet sanding is bad or wrong, we just don't want them to jump in blind and mess something up. There is no doubt that wet sanding can be highly effective at removing certain types of defects and, to be completely honest, it can be great fun. We just want people to be aware of what can go wrong if they don't know what they're doing.

Truthfully, it's not as hard as it sounds. Many people on Autopia have done it. They started without any experience and had never damaged any cars from doing it.

Never? Really?

[KC's]

Re: Mercedes 500 Complete wetsand

yes nice work