Blocking Clear Coat for Re-Painting - Chevelle Tech

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post #1 of 9 (permalink) Old Apr 25th, 11, 11:09 AM Thread Starter
steve
 
Join Date: Apr 2011
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Blocking Clear Coat for Re-Painting

I have read on here that it is ok to block clear coat, seal and paint over it.

A couple questions:

1 - I will block with 600-800 grit. Do I sand down to the old primer or is it basically just scuffing the clear?

2 - Should I be wet sanding or dry?

3 - To seal my guess would be to use epoxy. Correct?

Thanks
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post #2 of 9 (permalink) Old Apr 25th, 11, 6:24 PM
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Eric
 
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Re: Blocking Clear Coat for Re-Painting

No need to seal it, waste of material, waste of money, added chance of messing up.

Sanding with 600-800 is just fine. IMO any finer then 800 and the paint is easier to run, plus the coarser grit levels out the orange and urethane peel. Yes there is a difference between orange and urethane peel, but that's another story.

You don't want to break through the existing clear coat, you break through the clear coat you run the risk of lifting the underlaying basecoat. Basically sand enough to remove the gloss of the clear, you are simply scuffing it up, not removing it...Eric

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post #3 of 9 (permalink) Old Apr 26th, 11, 9:03 AM Thread Starter
steve
 
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Re: Blocking Clear Coat for Re-Painting

Perfect. That was the answer I was looking for... Thanks for the quick response
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post #4 of 9 (permalink) Old Apr 26th, 11, 9:19 AM
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Eric
 
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Re: Blocking Clear Coat for Re-Painting

Quote:
Originally Posted by lasemase72 View Post
Perfect. That was the answer I was looking for... Thanks for the quick response
I would use 600 and warm soapy water which aids in lubricating the surface when sanding.

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post #5 of 9 (permalink) Old Apr 27th, 11, 11:05 PM
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Ken
 
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Re: Blocking Clear Coat for Re-Painting

I prefer bubbles with my warm soapy water and a rubber duck
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post #6 of 9 (permalink) Old Apr 28th, 11, 7:31 AM
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Re: Blocking Clear Coat for Re-Painting

is the body straight? are you just sanding to repaint, or do you want to straighten the body
you will need something coarse if leveling, and you will go thru the clearcoat then, and reseal

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post #7 of 9 (permalink) Old Apr 28th, 11, 9:13 AM
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Roger
 
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Re: Blocking Clear Coat for Re-Painting

You use water because the sandpaper is such a fine grit that it would fill up after a couple strokes of sanding. A constant clean supply of water trickling where your sanding keeps your paper clean and makes a sheet of sand paper last a long time. As mentioned, you don't want to break through the clear but if your car body is wavy, now is the time to straighten it out and that means breaking through the clear in the bad spots. You planned on re priming any way.
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post #8 of 9 (permalink) Old Nov 8th, 11, 3:36 PM
 
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Re: Blocking Clear Coat for Re-Painting

How would you guys go about shooting base onto a small area where the clear coat seems to have faded completely?

It's for a bumper and well most of the clear is intact...and I would like to 800 grit it as well and then shoot over with clear. But there may be a suspect part of the bumper where the clear has failed and Im contemplating shooting this little area with a little base due to the fact that it looks lighter than the rest.

Im just not sure on how to properly finish it in regards to sanding since the surounding areas would be scuffed up with 800.....how would you leave the base?

I'm stuck between smothing over the exposed base with some 1500 then shooting the small area with new base......then blocking the rest with 800 grit for the clear. Gets a little confusing on what I should do first ..u know the order.

How did this project turn out? I'm curious on how re-clearing looks?

also I want to use 800 unigrit from meguiars since the clear is fairly thin...and I dont want to risk exposing more base...any reason that isnt a good idea?
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post #9 of 9 (permalink) Old Nov 8th, 11, 6:30 PM
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Randy
 
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Re: Blocking Clear Coat for Re-Painting

If the clear is failing in some areas it won't be long before it fails other places. Sand it off and seal it, then repaint. Better to do it now than to have it all fail with new paint over it.
As far as grit of sandpaper to use I might get some grief over this but I don't use anything but 400 grit before applying new paint. I have found over time that the courser paper gives the new paint better adhesion, and I actually believe I get fewer chips from road debris. But you have to be careful with metallics when using courser paper as it can leave scratches in the base.
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