Color Sanding MDF

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Old 05-08-09, 06:09 PM
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Color Sanding MDF

If I paint my MDF with a black oil-based paint, then try to sand it to make the coat smooth, won't it embed the sanded dust into the coat and/or make the paint look gray from sanding?

I recently painted a MDF coffee table and was afraid to experiment as it *had* to look good but I experimented in a small corner with sanding the paint coat. When I sanded it, it went from black to gray as I sanded paint off. It didn't simply 'flatten out'. Instead, it turned grayish.

Additionally, I tried, in a small corner, sanding my overcoat of Shellac. That caused the Shellac to also appear dusty and I imagined that it would make the finish cloudy instead of clear (from the abrasive surface over the clear).

What was I doing wrong? And how can I get something like this with MDF:


Thanks!
 
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Old 05-08-09, 06:18 PM
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Sure once you sand it down, the paint coat may take on a gray color. That's not the point. You now have a super smooth surface to recoat with more paint for a higher luster. You are waiting until the paint is completely dry before you sand it, right? Likewise your clear finish will need to be reapplied once you achieve a super smooth surface.
 
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Old 05-08-09, 06:24 PM
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Originally Posted by chandler View Post
Sure once you sand it down, the paint coat may take on a gray color. That's not the point. You now have a super smooth surface to recoat with more paint for a higher luster. You are waiting until the paint is completely dry before you sand it, right? Likewise your clear finish will need to be reapplied once you achieve a super smooth surface.
So how does one achieve an absolutely smooth black finish? I feel like if I get a super smooth surface to recoat on, I will still have the unevenness that I got from brush strokes in the first coat after I repaint (the whole reason why I was sanding to begin with)?

 
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Old 05-09-09, 04:00 AM
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It isn't feasable to get a super slick finish with a brush but you can come close. Are you thinning your paint any? what type of brush are you using?

The only way to get a finish like the pic is to spray the primer and paint.
 
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Old 05-09-09, 04:42 AM
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There are two ways of getting a paint to shine.

The most common way a paint is made to shine is chemically.
Enamel paints get their shine from solvents in the mix that rise to the surface of the film as the paint sets up.
The make up of the chemical that rises to the top of the paint film will determine the amount of gloss.
A variation of this is the automotive base coat/clear coat finish where you separately apply a colored base coat and top it with a clear finish.
The other way to get a shine is to use a lacquer paint that is meant to be sanded.

If you want a smooth gloss finish you should use Mark's suggestion and use a spray finish but you would have to remove the bad paint first.
To fill minor scratches when you are finished sanding the base material an automotive sanding primer works well.
 
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