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Primer over oil base paint - still need to sand/prepare surface?

Posted by kimcoco (My Page) on
Sun, Feb 20, 11 at 16:53

Asking the professionals --

I'm repainting oil based painted trim in my bath with latex.

I am priming the oil base paint with latex primer, and then applying latex paint.

Do I still need to sand/prep the surface before I apply latex primer?

I've already tested with denatured alcohol to determine that it's oil based paint.


Follow-Up Postings:

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RE: Primer over oil base paint - still need to sand/prepare surf

I'm not a pro so I'll tune in later .......

I thought you had to use an oil based primer over oil based paint.
I've been looking at the new Smart Prime by Zinzer that's water based but acts like an oil based.That probably doesn't count.


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RE: Primer over oil base paint - still need to sand/prepare surf

Ditto on the oil based primer over oil based paint. And yes, you'll still need to sand before priming, especially on oil base, until the surface is evenly dull.


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RE: Primer over oil base paint - still need to sand/prepare surf

I have to disagree about the primer. I go to a reputable paint store (not a box store) and also know a pro painter - I've been told that you can prime over oil based paint with a latex primer.

Whether I have to sand before priming with the latex primer is the real question.


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RE: Primer over oil base paint - still need to sand/prepare surf

Hey KimC!

Yes...IDEALLY...do a thorough scuff-sand with 100-grit paper!
It's the BEST way-period.

Also YES...Latex primers are perfect over Oil paints (AFTER SANDING!). It's done all the time. You CAN use an Oil primer as well...AFTER SANDING!
>>> Obviously, Latex topcoats are ideal over either type of primer.

Sanding, in a sense, creates the "broom finish" that you need on sidewalks, so they're not slippery. Why don't you slip on broom-finish sidewalks??
Obviously it's because of the "surface-profile" that's created.

SAME IDEA for scuff-sanding a smooth finish Oil (or ANY glossy) paint. You create a profiled surface that your new Latex primer can grip VERY well. In turn, your paint topcoats bond very well to the new primer.

>>> Result??
* A paint/primer film that's bonded well, BOTH physically (from sanding), AND chemically (the paint-to-primer bond).
* Thus, you have a paintjob that'll stand up to the hard-knocks of real life!
* Make sure you're using at least a Satin-sheen paint!

Faron


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RE: Primer over oil base paint - still need to sand/prepare surf

As usual, Faron to the rescue.

And from dannylipford.com:

"While it used to be necessary to apply oil-based primers over oil-based paint and latex primers over latex paints, many primers today allow you to switch between them as long as you PREPARE THE SURFACE PROPERLY. When painting over interior oil-based woodwork with latex, be sure to sand or degloss the surface first, then paint with a BONDING PRIMER before topcoating with latex. Painting over multiple layers of oil-based paint on the outside of older homes with latex paint can cause adhesion problems, so in that situation, you're better to continue using oil-based house paint."

We used to tell people you couldn't paint plastic, either...technology changes.

Here is a link that might be useful: Homeowner’s Guide to Paint Primer by Jerri Farris


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