How to damp-sand?

[Mary S]

Re: How to damp-sand?

Mary, you can also you a pneumatic DA to wet sand as well. Damp Sanding and Wet Sanding can both be used with DA's.

In a nut shell, you would want to damp sand if you are fixing a specific defect in a car that require sanding, but you don't want to wear down the orange peel because the rest of the car and panel has orange peel. Otherwise if you wet sanded the area, there would be a spot that has no orange peel and the rest has orange peel and that just wouldn't look too great.

Thanks, Andrew. I'm obviously still a bit confused. I know I have checked the air compressor power it takes to power the 6" pneumatic DA, and it takes a pretty big air compressor to do it. So in my case, I could only do it with a motorized DA. As I said earlier, Mike Phillips did a Show Car Garage recently with damp sanding and was recently in the process of editing the video and I think an article too to put out on the site. I am hoping that will clear a few things up a bit.

I may give up the idea of damp sanding altogether and just wet sand by hand. And since my first pass will be by hand anyway, subsequent steps, if I use foam finishing pads, will follow the contour of whatever I left behind in the first one.

[Andrew C.]

Re: How to damp-sand?

You could try using the new circular hand sanding pads (you can also use them to attach polishing pads) if you would prefer to go by hand, this way you could either damp sand or wet sand. What exactly are you going to be sanding and what are you trying to accomplish?

[Mary S]

Re: How to damp-sand?

You could try using the new circular hand sanding pads (you can also use them to attach polishing pads) if you would prefer to go by hand, this way you could either damp sand or wet sand. What exactly are you going to be sanding and what are you trying to accomplish?

Thanks, Andrew, I forgot about the circular pads, and also the 3 inch ones. That may be the way to go for small areas.

I have 2 issues with my car. It is 13 years old and it has swirls, has never been buffed (although since it is white the swirls are hard to see). And it has fairly mild orange peel, but that is pretty obvious in reflections as in the doors. What I wanted to accomplish is since I am going to level the surface some to eliminate the swirls, to use a sanding process at the same time to partially level the orange peel. I know it is not advisable to completely remove orange peel from factory paint.

I did some testing on my scratched up BMW hood with orange peel paint, and with 3000 grit and about 40 strokes wet sanding, that is pretty much what I got. It didn't remove the orange peel but made it a bit smoother, and it also eliminated the surface scratches. All I did to remove the sanding scratches was use 205 with a rotary and a polishing pad.

To get the same effect as far as the scratches go, I had to add a couple of rounds of compounding with 105 prior to using 205. And, to be honest, it didn't quite do as good a job on the surface defects either. So the 3000 grit saved me a couple of rounds of compounding plus flattened the orange peel enough to make it worthwhile

So my next step is to try that on a test spot on my car. I don't think it will take 40 strokes to accomplish what I want to do since I believe the paint is softer (BMW has pretty hard paint) and the surface defects are much lighter.

It may be then that I don't need to damp sand at all, although I think if I did I would get an even finer finish. I just don't have the sanding discs yet.

[Michael Stoops]

Re: How to damp-sand?

Damp sanding vs wet sanding should be looked at as a complete system and not just simple alternatives. Most wet sanding papers are designed for just - full wet sanding. For maximum result these papers need to be soaked in water overnight and the surface needs to be almost flooded with water during the process. As with anything, there is a right way and a wrong way to do this. If you use paper designed for full wet sanding but you're not using much water or not soaking the paper prior to use, you're doing it wrong and won't achieve maximum results.

Damp sanding discs are designed to be used with much less water and overuse of water will actually cause a hydroplaning situation that will reduce the amount of cut. With our Unigrit Sanding/Finishing Discs the abrasive slurry bonded to the backer should not be used fully wet or soaked.

Overall, the damp process tends to be a bit cleaner, less resource intensive and every bit as effective as full wet sanding.

[Mary S]

Re: How to damp-sand?

Michael are the damp sanding discs synonymous with the foam-backed discs? In other words, 1500 and 3000 foam backed disks are made for damp sanding, 1500 regular sanding disks are made for wet sanding?

[Mary S]

Re: How to damp-sand?

Here are the images from the testing I did the other day on my BMW test hood.

The purpose: To eliminate swirls and smooth the orange peel some with the wet sanding with 3000.

This is pretty much what I had to start with. Light scratches and swirls.



After I wet sanded (regular Unigrit 3000 by hand, 40 strokes forward and back) followed by 205 on a polishing pad on a rotary to remove sanding scratches. No compounding needed. Orange peel is still there but a little smoother. Scratches mostly removed.



Then I did this section using no wet sanding but 105 on a polishing pad with a rotary twice, followed by 205 on a polishing pad with a rotary. The scratches are a little rougher than with wet sanding. No correction to the orange peel, as expected.



A half-and-half picture. Wet sanding on the right, compounding on the left.



The initial scratches are much worse than on my Explorer. I really have only light swirls on the car. So I will do this test on a spot on my car next. I expect less sanding will be needed to eliminate the swirls. I would anticipate the orange peel to be a little smoother but not eliminated by virtue of the wet sanding.

A damp sanding step with a 3000 6" Unigrit disc would probably refine the finish further. However, it probably won't be necessary since the 3000 comes out so easily with 205, and I don't have the Unigrit discs to try this with at this point in time. So my plan is most likely I will only wet sand by hand with Unigrit 3000 sanding paper. Again, the goal to remove swirls and partially smooth the orange peel.

[Mary S]

Re: How to damp-sand?

This is the best shot I could make to compare the orange peel with compounding and no wet sanding (left) and wet sanding no compounding (right).

You can see the line where I had put the tape to divide the two; however, the tape did keep coming up on the edge while I was wet sanding, hence the border isn't perfect. It is obvious the orange peel is still there on both sides. It is just a bit smoother on the right. The distortion in the light reflection is because the hood is curved up on that side near the edge of the hood.

[Michael Stoops]

Re: How to damp-sand?

Michael are the damp sanding discs synonymous with the foam-backed discs? In other words, 1500 and 3000 foam backed disks are made for damp sanding, 1500 regular sanding disks are made for wet sanding?

Not necessarily. When dealing specifically with our 6" discs all are designed for damp use. The foam backed discs are finishing discs while the film backed discs are sanding. This means the film backed sanding discs are more aggressive than the foam backed finishing discs. As mentioned previously, a 1500 grit foam backed finishing disc will be less aggressive than a 1500 grit film backed sanding disc. The little extra foam cushions the blow, so to speak.

Now, when you start talking about headlight repair and you're dealing with the 3" diameter 320 grit to 800 grit film backed sanding discs (there are no foam backed finishing discs in these grits) then you're talking about dry sanding. Yes, dry.

Nice testing you did on the BMW test hood, too. It's really nice to see you moving very slowly and methodically here as well, and understanding the potential downfalls to what you're thinking about. Keep in mind that hand sanding is more aggressive than D/A sanding and for what you're considering, definitely stick with those very fine grit papers. Keep them very clean so as to avoid any tracers, too.

If you're really planning on doing this to your Explorer, and I know we've talked about this and you've been a part of many such discussions, just be extremely cautious and don't push it. That's old factory paint you're dealing with and factory paint and sanding don't always mix well. Honestly, that warning is less for you personally and more for those individuals who might read this in the future.

[Mary S]

Re: How to damp-sand?

If you're really planning on doing this to your Explorer, and I know we've talked about this and you've been a part of many such discussions, just be extremely cautious and don't push it. That's old factory paint you're dealing with and factory paint and sanding don't always mix well. Honestly, that warning is less for you personally and more for those individuals who might read this in the future.

The cautions bear repeating:

What a Detailer Should Know About Clearcoats:

Although clear coats do provide additional protection, there is a limit as to how much clearcoat can be removed in the buffing or wet-sanding process without jeopardizing the long-term durability of the paint finish. When too much clear is removed by wet-sanding or buffing the problem is often not visible to the naked eye. In fact, the results must look fantastic. However, you can bet the UV protection has been dramatically reduce to the point that they color coat will be negatively affected by the sun and other factors.

For these reasons all car manufacturers now specify that the paint thickness be measured in 0.1mil, or 1/1000th of an inch before and after any wet sanding or buffing. If only 0.5 mils of clearcoat has been removed the integrity of the clearcoat is in danger. And, manufacturers could void a warranty if they know about this.

The following are the maximum allowable clearcoat reductions the major USA car manufacturers will allow: Chrysler 0.5 mils; Ford 0.3 mils; GM 0.5 mils.

As a professional detailer you really should have a paint thickness gauge and it should be used on every car that you will be using a high speed buffer and compound on to correct a paint finish problem. In principle you owe it to the customer, and you owe it to yourself should you damage the paint, or have the customer come back at some later time with paint damage.

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Basically, Ford says don't remove more than 0.3 mil from your factor clear coat. Other manufacturers allow 0.5.

So what I am considering, most importantly, I won't do it if more than 0.3 will be removed. And I know it won't remove the factory orange peel.

Secondly, my car is garaged most of the time. And the only horizontal surface that I would consider wet sanding is the hood. I don't care about the roof. And if I needed to repaint the hood I would be willing to do that. That would be a simple refinish.

So in summary, it is not wise to attempt to remove factory orange peel from a car by wet sanding. In general, the orange peel will be thicker than the parameters of the amount the car makers allow to be safely removed from the clear coat.

[Michael Stoops]

Re: How to damp-sand?

Michael are the damp sanding discs synonymous with the foam-backed discs? In other words, 1500 and 3000 foam backed disks are made for damp sanding, 1500 regular sanding disks are made for wet sanding?

Yeah, we wanted to reiterated what's been said many times before, but you hit it out of the park!!

What's not included in the info you supplied is this: Clear coat contains the UV inhibitors that protect the color coat, and when the clear is sprayed those UV inhibitors tend to rise to the surface of the clear. So removing a small percentage of clear will remove a relatively large percentage of UV protection. Sanding all the way through your clear coat means damage is done NOW. Everybody understands this and can see it. But sanding just a little to far into your clear coat means damage down the road. But visually you can't tell if you've removed 0.2 or 0.7mils of clear.

[DrdetailNashville]

Re: How to damp-sand?

Very interesting stuff guys and girls. I have a question, sometimes orange peel can be in the actual paint layer not only in the clear coat. I have wet sanded (I have never tried damp sanding) cars where I believe this was the case. I didn't want to sand any more for fear of removing too much clear coat.

Am I wrong about this? Is orange peel only in the clear coat?

[Michael Stoops]

Re: How to damp-sand?

The problem with trying to level orange peel in factory paint is that there simply is not enough clear coat film available to safely allow total removal of the orange peel. With an aftermarket paint job the paint can lay down additional clear so that it can be safely, and completely, leveled.

But any peel you're seeing is just in the clear. Once that is sanded flat (assuming you're working on paint with sufficient film build) then the paint will be flat. Period.

Now, if by some strange reason there are sanding marks or other similar defects present in the color coat they may well be visible through the clear. Obviously you can't do anything for this sort of defect. But even if there was orange peel in the color, leveling the clear would eliminate any visible evidence of it.

[Mary S]

Re: How to damp-sand?

Well, I think the bottom line is I have given up on trying to wet sand my car with 3000, at least for now. I gave the 3000 another run on the test hood this past weekend, and this time I tried pulling the sanding marks out with the G100V2 and 205 with a polishing pad. It worked great, except there were tracers. I didn't know it at the time, but they were pretty deep.

I think I realize now that these probably happened because I did something wrong. Maybe because I didn't clean the surface again since I worked on it last, or something. I kept stepping up the aggressiveness scale to try to get them out, and nothing was working. And by the time I got to the rotary with 105 and a wool pad, the 105 kept drying out, and the surface was getting hot. By this time I wasn't even trying to watch the edge that was facing me, and I took some paint off the edge. I eventually got the tracers out, and the area of the hood after all that did look pretty good, with the orange peel much smoother than the unsanded side.

So I'm a bit freaked now because of the tracers. I am not convinced I can prevent them and I don't want to risk having to go through this on my car.

I just got a Brinkmann Xenon lantern the other day so I can see what I am dealing with on my car. Notwithstanding that this is a white car and they are hard to see, I think the swirls are pretty light and that 205 with the DA should probably get them out. I may have to step up to 105 in spots but I don't think I will need the rotary. So I am just going to go ahead and take them out and drop the idea of wet sanding any time soon.

[InfiniteDetail]

Re: How to damp-sand?

Mary, that's pretty much par for the course. I usually have tracers, even with 3000, and usually have to hit the area with the rotary, maroon wool solo, and 105 at least twice.

Just tape up those edges first

Don't be discouraged, the next time out you know what to expect and it'll go alot smoother

[Mary S]

Re: How to damp-sand?

Mary, that's pretty much par for the course. I usually have tracers, even with 3000, and usually have to hit the area with the rotary, maroon wool solo, and 105 at least twice.

Just tape up those edges first

Don't be discouraged, the next time out you know what to expect and it'll go alot smoother

Thanks for your encouragement! I will practice this some more but on my test hood. For now I think taking out just the swirls will be my first step on the car.