Wet Sanding... pulling out new paint?

[c8n]

My wife had a run in with a fence that left some nasty deep scratches. The scratches are all over the bumper and it had to be painted so I figured before I do this, why not try a little wet sanding.

So about a week or so ago, I wiped down the bumper with wax/grease remover and applied dealer touch up paint with a very fine brush. I also allowed a couple of days for the paint to dry and waxed the area with Meg's NXT. I should mention that the car was driven and there has been some rain. Fast forward a week and this weekend, I do a wipe down on the bumper and proceed to wet sanding starting with 1500 to level the paint until smooth and then proceed with 2000, 2500 and then 3000. I then took my DA with Meg's MF cutting pad with M105 and go over the area to remove the sanding marks. The MF pad and M105 did a great job of removing the sanding marks but it looked like a some of the touch up paint was removed and some of the scratches remained. It definitely looks better but almost looks like some of the touch up paint was pulled out of the scratches?

Did I miss something when I applied touch up paint for this to happen?
Would appreciate some insight.

Thanks

 

[Mike PhillipsMike Phillips is verified member.]

but it looked like a some of the touch up paint was removed and some of the scratches remained.

Did I miss something when I applied touch up paint for this to happen?
Would appreciate some insight.

Thanks

My experience is if you heat up the area you're buffing the touch-up paint can and will simply pull out of the defects. Probably an adhesion or not sticking to the surface issue.

Besides cleaning the surface to be painted and even roughing it up if possible, the next two things you can do are,

1. Allow the paint to fully dry and harden.

2. Don't get the area hot when buffing, so buff just a little than stop, etc.


:dunno:

 

[E-WAY]

You forgot to apply the clear coat.

 

[c8n]

Thanks Mike.
The paint was sitting for about a week but I did feel a little heat after buffing. However, it definitely wasn't hot. Typical amount of heat after a buffing section on plastic. Is it possible that the MF fiber would pull out the paint? Should I use a a foam pad instead?

 

[c8n]

You forgot to apply the clear coat.

When I asked the dealer parts guy about clear coat, he basically said that it was not needed as the touch up has clear mixed in.

 

[Mike PhillipsMike Phillips is verified member.]

Thanks Mike.
The paint was sitting for about a week but I did feel a little heat after buffing. However, it definitely wasn't hot. Typical amount of heat after a buffing section on plastic.

What happens is the touch-up paint becomes rubbery and it simply pulls out. Been there done that...

This is why I tell most people that in a lot of cases, more and more work doesn't always mean better and better results. In your case it's no big deal since you're going to have it repainted.

For a lot of people though, aiming for perfection but not having the skill, experience or time or right tools, (fill in the blank), they can easily take a mole hill and turn it into a mountain.

Is it possible that the MF fiber would pull out the paint? Should I use a a foam pad instead?

I think anything moving over the surface can and will pull the touch-up paint out of the defects. Even if working by hand... I've done it.

 

[Setec Astronomy]

IMO you're looking for perfect adhesion of the paint in a very imperfect environment. Let's look at all the obstacles:

1. Touch up paint is lacquer, not as durable as catalyzed clear
2. Substrate is plastic
3. Defect is a scratch--how clean is it really at the bottom of the scratch?
4. Defect is a scratch--how much surface area is there for the new paint to adhere to?

 

[E-WAY]

When I asked the dealer parts guy about clear coat, he basically said that it was not needed as the touch up has clear mixed in.

Dealers don't provide the clear they just tell its fine but it requires clear. Touch up paint becomes a single stage.

 

[c8n]

What happens is the touch-up paint becomes rubbery and it simply pulls out. Been there done that...

I think anything moving over the surface can and will pull the touch-up paint out of the defects. Even if working by hand... I've done it.

IMO you're looking for perfect adhesion of the paint in a very imperfect environment. Let's look at all the obstacles:

1. Touch up paint is lacquer, not as durable as catalyzed clear
2. Substrate is plastic
3. Defect is a scratch--how clean is it really at the bottom of the scratch?
4. Defect is a scratch--how much surface area is there for the new paint to adhere to?

Great points...
What prep work would be necessary for good adhesion on plastic and metal surfaces?
Mike mentioned "roughing it up" when cleaning... some elaboration on this would be appreciated. It's probably too late for me as I have already applied touch up paint on all affected areas but I am sure other AG'ers would like to know... and as would I for future references.

 

[Setec Astronomy]

The point is I'm not sure you can prepare a scratch well enough to get a perfect condition. The other thing to think about with your drying time is if you have the typical touchup "blob" it's many times thicker than a coat of sprayed paint, and it may take longer to dry or may never dry properly at the bottom of the scratch if it's "sealed in" by the top of the blob (well, never is a strong word, but think about leaving a can of paint open and it crusts over on the top and stays liquid underneath). It might be that you want to blob, give it a week to dry, sand it, then give it another week before polishing.

 

[c8n]

I think I am going to try that.
Wet sand and let it dry and cool off and then polish the following day.