Do I have to go down to bare wood like the paint store guy told me to do?


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Old 11-11-08, 10:03 AM
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Do I have to go down to bare wood like the paint store guy told me to do?

I just painted all my bathroom wood trim and a built-in sink cabinet with latex mildew resistant paint. I previously had painted everything with oil-base years ago. I was going to go with oil again but the Lowe's guy talked me into latex.

I washed everything with TSP and sanded most areas before I painted.

The windows were so bad I sanded what I could to bare wood (maybe 10% is exposed) and primed with some "1-2-3" stuff (I think that's what it's called) then 2 coats of this latex mildew resistant stuff. That was 5 days ago and I could, today, scrap parts of it off with my nail if I tried to - but it wouldn't come off easily.

I noticed the the instructions on the can of latex says it's self-priming so I didn't bother priming the rest of the woodwork and proceeded to apply two coats to the sink cabinet and door frame. A day later it looked great - until I accidently dinged it with my nail. I then tested the adherence further and was able to peel off the paint in one big sheet! I then tested the door frame and it peels just as easily.

Maybe it hadn't had time to cure I thought. Just leave it a week.

I called a paint company and was told I HAVE to remove ALL of the paint to bare wood - that is the ONLY way any new paint will adhere. He said I should have sanded more (the sanding I did didn't even produce dust - the old paint is very hard and shiny) and should have used a latex primer (even though the can says it's self-priming). Now he says I can't just simply peel off the new paint and sand more as it will not work - that by painting with the latex without priming I've interfered with the ability of any (oil or latex) new paint from ever adhering again.

Is this true? Do I have to remove not only all the new latex paint but also ALL the old oil-based? If so - how?

I also painted the inside of the cabinet and it appears to be holding okay there - can I leave be whatever doesn't peel off or do I need to scrap it too?

This seems so extreme. I mean - people paint latex over oil all the time and surely it must work some of the time.

Any help will be appreciated.

Thanks.
 
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Old 11-11-08, 11:42 AM
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Yes, a claim of "self priming" usually refers to it's priming capabilities over bare wood or drywall.

You will need to scrape off all of the failing paint, and then prime with an oil-base primer. (I quality water-base bonding primer would probably work too, but I wouldn't risk it since you are already having problems.) There is no need to sand to bare wood, just the stuff that is not adhering.

Also, specifically what paint were you using?

SirWired
 
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Old 11-11-08, 11:48 AM
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You don't necessarily need to sand down to bare wood but you do need to remove everything that is loose or not sticking -- that would be most of what you just painted over tha oil base paint. A way to avoid this would have been to prime everything with the BIN or Kilz Shellac based primer (I believe that is the 123 you mentioned) Shellac based primer will stick to almost anything. You can even use it to paint over crayon or magic marker. It dries quickly and provides a good base for your new latex paint.
 
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Old 11-11-08, 12:23 PM
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I used Zinsser Perma-White Mold & Mildew-Proof Interior Paint.

I assumed since Zinsser also makes the '1-2-3' primer I used on the window that it would be okay to use their paint without priming (again since the can says "self-priming"). There was no good reason for my NOT using the '1-2-3', I have plenty left, it was a dumb decision solely based on what I read on the can.

So...let me recap what I've learned here...

- I only have to remove the fresh latex that comes off easily.

- I do not have to remove the old paint

- I can recoat with either the '1-2-3' primer I already have or the shellac primer

Do I need to sand or clean with TSP again to remove any residue that might be left from the latex paint?

If sanding is adviced, should I use a coarser grade of sandpaper? as the 80 grit I used didn't seem to scratch the surface (pun intended). I don't want to put gouges in the old paint though.

Thanks again...
 
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Old 11-11-08, 02:46 PM
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Anytime you apply latex over an interior oil base enamel [or poly/varnish] you need to sand and coat the enamel with an oil base or shellac based primer. If I remember correctly the bulls eye 123 is a latex primer. Kilz doesn't make a shellac primer but their original oil base formula will do ok.

It would probably be best to start your sanding with a 60-80 grit, it will leave a lot of scratches but you can finish sanding with 120-150 grit, prime, sand with 220 and it should look nice.

I'd skip the TSP, it is a great cleaner and gloss reducer but it must be rinsed well! I only use it on the exterior.
 
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Old 11-11-08, 07:09 PM
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Ditto.

My rule is the same as Marksr. Even though the 123 Bullseye may develop adhesion over time (the next 2-4 weeks), it will be sensitive to marring when used over a hard glossy enamel, and even blistering if it gets real wet in the mean time.

Latex paints develop adhesion and hardness as they cure. They dry fast, but cure rather slowly. Dark colors which are full of slow evaporating glycol can take even longer to cure.

For this reason an oil primer works best to convert the old oil painted substrate over to latex. Shellac works well too but is a bit brittle for my use - in a bathroom which is subject to great temperature changes.
 
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Old 11-11-08, 07:36 PM
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I didn't read your post closely. You did not prime with anything over the rest of the trim etc..

Was it Zinsser's Perma White that you used?

If you used Zinsser's bathroom paint (it is now called Perma White), it is self priming over glossy surfaces with adhesion pretty much like 123 Bullseye ........ but subject to the same issues. Curing will occur over the next few weeks.

When painting over a glossy surface with a latex bonding primer (or self priming paint - like Perma White), you need to be sure the surface is impeccably clean or the paint/primer which is supposed to stick to glossy surfaces - won't stick.

Oil primers and paints are a little more forgiving.
 
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Old 12-02-08, 04:49 PM
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Remove all the failing paint, scuff sand, prime with oil based primer, let dry, sand primer for a nice smooth finish. Then top coat.


Sean
 
 

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