Meguiars Unigrit 2500, 3000 and factory orange peel

[Mary S]

Hi, I was reviewing the Meguiars training video How to Remove Paint Defects the other day, and at 12:09, when they were talking about Unigrit sanding paper, they said that the 2500 and 3000 grits were designed specifically for using on factory orange peel.

I know there are great cautions about trying to use wet sanding to remove factory orange peel in terns of taking off too much clear coat and affecting the UV protection. And I know you have to use a rotary to buff out the sanding marks. I have used 2000 grit on a test junk hood and had great results with it, at least cosmetically.



But I suspect the factory orange peel on my car will always bother me, so my question is just that if sticking to 2500 and 3000 grit wet sanding, is this relatively safe for factory orange peel? Is there data as to how many mil this process will take off of the clear coat?

[Mary S]

Re: Meguiars Unigrit 2500, 3000 and factory orange peel

Removing Orange Peel & Sanding Marks with the Griot's ROP and the Wolfgang Twins

I found this link which was helpful. What they found was their process took off an average of about 0.5 mil.

And what I have read is Ford recommends you could take off 0.3 mil off to be save (it is lower than the other manufacturers, who recommend 0.5).

What I don't have, unfortunately, is a paint gauge. The one they use in this link costs over $600!

It looks like for sure if I try this I need to leave the 2000 grit out of the equation and go right to 2500 and/or 3000.

[Michael Stoops]

Re: Meguiars Unigrit 2500, 3000 and factory orange peel

How you actually sand, almost regardless of the paper itself, will also impact how much paint you remove. Wet sanding by hand is, surprisingly enough, more aggressive than D/A sanding. In fact, even when properly done, it is generally considered that the difference between hand and D/A sanding is almost a full grit range different - that is to say 2000 grit D/A sanding is actually similar to 2500 or even 3000 grit hand sanding. Sanding with a D/A (we're generally talking about dedicated pneumatic tools here) is less aggressive overall because it tends to be much more uniform than hand sanding and it covers a larger area more quickly and accurately. This uniformity of cut delivers a very predictable sanding scratch that can be removed very easily with even a foam cutting pad rather than needing to step up to a wool pad.

That said, when D/A sanding, we generally talk about either a "sanding disc" or a "finishing disc". Even when looking at equal grits a true sanding disc will be more aggressive than a finishing disc. This is because of the foam backing built into the finishing disc, which you can clearly see in the side on view of two 1000 grit discs shown below:


The disc on the left is a finishing disc as evidenced by the foam backer. This foam, used in conjunction with a still thicker foam interface pad between it and the actual tool, allows the abrasive material to follow contours even as fine as orange peel. This means you can remove scratches from the paint without actually leveling the paint. This can be very important when you've got severe defects on one panel and not on an adjacent panel; you can sand out the severe defects without eliminating the orange peel and making one panel appear visually quite different from the one next to it.

The disc on the right, while of the exact same grit spec, is more aggressive since it can't follow contours. This will mow down orange peel, making the paint truly flat. That also means it will remove a lot more paint than the exact same grit finishing disc will.

In this image you can see sanding marks throughout, but the orange peel is only evident on the left side. Both sides were D/A sanded using the same grit paper, but the left side was done with a finishing disc while the right side was done with a sanding disc.


So, your thoughts on sticking with 3000 grit paper to hand sand the orange peel on your factory paint job is smart. To a point. If you get (even a little) overly aggressive with this process, and then you get (even a little) overly aggressive with the rotary buffing process, you can easily remove that 0.3 mil limit. What happens then? How much more buffing can that paint take in the future? What do you do about defects that arise down the road, even just typical swirl marks? From a paint health & safety standpoint you don't have much of anything left to play with - you're pretty much done buffing that paint. Forever.

Far too often we see people jump into wet sanding when they have no clue what they're doing and they always come back with a comment like "well, I wasn't pulling any color when buffing so obviously I didn't sand through my clear coat, so what's the big deal?" Well, the big deal is that you don't need to go "through" the clear. You only need to remove enough so as to compromise the amount of UV inhibitors in the clear. Ford may be recommending removal of no more than 0.3 mil while other companies use 0.5 mil as a limit, even though the clear itself is 1.5 to 2.0 mils thick. Why so little then? The UV inhibitors tend to rise to the surface as the paint cures so removing even this small amount of clear removes a large percentage of the UV inhibitors. This ultimate leads to clear coat failure, most likely through delamination of the clear, since the paint's built in protection has been severely compromised. You don't have to go anywhere near being "through the clear" in order to have problems down the road.

You've got that test hood to play with, which is fantastic. But overall, wet sanding to fully remove orange peel from factory paint is generally not a recommended process unless you possess a pretty darn high skill level. But wet sanding can let you do some pretty cool things when it comes to severe defect removal and if you're serious about detailing and paint care in general, even if just for your own vehicles, it's a great skill to learn.

One last thing: Marcki, please understand when we talk about people jumping into wet sanding while totally clueless that we aren't directing that comment at you. You've obviously done a ton of research on this already, just as you did (and continue to do) with rotary buffing before. We wish more people would take the level headed, logical approach to things like you have been doing all along. You would be amazed how many people have started wet sanding on their personal vehicles - by hand, with cheap paper, no backing pad, with no concept of what's really going on. Then they want to know how to fix the problem because, well, ScratchX by hand just isn't doing it for them. But, hey, they didn't go "through the clear"! Yikes!

[HCAD]

Re: Meguiars Unigrit 2500, 3000 and factory orange peel

Great post Michael!

[Mary S]

Re: Meguiars Unigrit 2500, 3000 and factory orange peel

Thanks for the post, Michael! I know Mike Pennington talked about this briefly too in the Meguiars series on wet sanding.

If I do anything with the orange peel, I am going to have to be as super conservative as I can, which means wait until I have a DA to sand with, and wait until I have a paint gauge so I can measure the existing and final paint depth and see how much I am taking off, and use probably nothing less than a 2500 finishing disc.

And I know I shouldn't be thinking about it at all, and maybe I will give the idea up, but I just love the mirror-like reflections and the orange peel bothers me.

So far, my paint hasn't ever been buffed since it left the factory, so it occurred to me that if I am going to do it, now would be the time to do it, with the maximum amount of clear coat on the surface.

Anyway, thanks again for your post. I am taking all of this pretty slow right now, no plans to move on it any time soon.