wet/dry sanding

[DanaDetailingPros]

One thing Mike said on one of his recent sanding videos was, that sanding was for single stage paint only. And if you sand any new production cars it would just kill the clear coat. Then I see a ton of videos where they are demonstrating dry and wet sanding on new cars with great success.
I posted this on Autofordge.

[BudgetPlan1]

Then I see a ton of videos where they are demonstrating dry and wet sanding on new cars with great success.


I would be curious to know how that short-term great success plays out as time goes on. Isn’t one of the primary jobs of the clearcoat is UV protection?


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[DanaDetailingPros]

I would be curious to know how that short-term great success plays out as time goes on. Isn’t one of the primary jobs of the clearcoat is UV protection?


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I thought that same thing! I would guess that's the time to use a good LSP or coating. Still curious as well and like you said time will tell.

[2black1s]

Just for clarification...

As far as I am aware, Mike never said that you can't, or shouldn't, sand clear coats; or that sanding is only for single stage paints. What I have heard him say is that sanding "factory" clear coats is not the best idea, and sanding should be reserved for repaints, single-stage or base coat/clear coat, that will typically have a paint film thickness greater than that of a factory finish.

[DanaDetailingPros]

I tried to find the film. I gave up! To Many. About a month back.

[DanaDetailingPros]

Just for clarification...

As far as I am aware, Mike never said that you can't, or shouldn't, sand clear coats; or that sanding is only for single stage paints. What I have heard him say is that sanding "factory" clear coats is not the best idea, and sanding should be reserved for repaints, single-stage or base coat/clear coat, that will typically have a paint film thickness greater than that of a factory finish.

Not those words yes. But you described it perfectly.

[DUBL0WS6]

Sanding factory clearcoats is a bad idea. The uv protection is in the top of the thin clear. So while you can get away with it the chances are that eventually the clear will fail.

A repaint with multiple coats of clear is a different story. They often get wetsanded with 2500 and 3000 and then buffed.

[2black1s]

Sanding factory clearcoats is a bad idea. The uv protection is in the top of the thin clear. So while you can get away with it the chances are that eventually the clear will fail...


I've seen or heard this claim more than once and I just don't believe it. Do you have any technical or scientific information to support this claim?

Here's what I believe...

When the clear coat is applied, factory or otherwise, it is a homogenous mixture. Therefore, any UV protection properties of the clear coat will be present throughout the clear coat film thickness. If you sand off 25% of the clear coat film thickness, then you have reduced its UV protection properties by 25%. Sanding off 50% will result in a 50% reduction of the UV protection, and so on...

My comments are based completely on my own logic. I don't have any technical or scientific proof, but I would have to see such that states otherwise to change my perspective.

[98CayenneTA]

I've seen or heard this claim more than once and I just don't believe it. Do you have any technical or scientific information to support this claim?

Here's what I believe...

When the clear coat is applied, factory or otherwise, it is a homogenous mixture. Therefore, any UV protection properties of the clear coat will be present throughout the clear coat film thickness. If you sand off 25% of the clear coat film thickness, then you have reduced its UV protection properties by 25%. Sanding off 50% will result in a 50% reduction of the UV protection, and so on...

My comments are based completely on my own logic. I don't have any technical or scientific proof, but I would have to see such that states otherwise to change my perspective.

I second this statement

[opie]

I trust the word from the painter. That makes sense to me

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[DUBL0WS6]

I've seen or heard this claim more than once and I just don't believe it. Do you have any technical or scientific information to support this claim?

Here's what I believe...

When the clear coat is applied, factory or otherwise, it is a homogenous mixture. Therefore, any UV protection properties of the clear coat will be present throughout the clear coat film thickness. If you sand off 25% of the clear coat film thickness, then you have reduced its UV protection properties by 25%. Sanding off 50% will result in a 50% reduction of the UV protection, and so on...

My comments are based completely on my own logic. I don't have any technical or scientific proof, but I would have to see such that states otherwise to change my perspective.

I'm not a chemist so I don't know for sure. I guess it would depend on molecular weight of individual components in the clear, the heavier solids would most likely settle to the bottom.

[2black1s]

I'm not a chemist so I don't know for sure. I guess it would depend on molecular weight of individual components in the clear, the heavier solids would most likely settle to the bottom.


If that were the case, then the finish of every panel would have a different final composition than the next based upon its orientation during painting, i.e., horizontal panels vs. vertical panels and everything in between. Additionally, it is my opinion that the viscosity of the clear coat is high enough that the mixture will remain homogenous throughout the drying/curing process.

Again, this is all predicated on my own sense of logic, and my painting experience... I'm not a chemist either.

[DUBL0WS6]

My thought is that we know that the solvents outgas from the paint. In other words, trapped solvent migrates to the surface. Does UV protection do the same thing?

I'm sure someone knows the answer for sure but not sure those people actually view these forums on a regular basis.

[2black1s]

My thought is that we know that the solvents outgas from the paint. In other words, trapped solvent migrates to the surface. Does UV protection do the same thing?

I'm sure someone knows the answer for sure but not sure those people actually view these forums on a regular basis.

Interesting theory. :xyxthumbs:

Looks like some research is in order...