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Old 08-30-2011, 12:29 AM   #1
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oil polyurethane over latex paint


I have painted over a wood table with black latex paint to match our other furniture components. This was the only black product available in our small town. Can I paint an oil based polyurethane over top?

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Old 08-30-2011, 02:00 PM   #2
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oil polyurethane over latex paint


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I have painted over a wood table with black latex paint to match our other furniture components. This was the only black product available in our small town. Can I paint an oil based polyurethane over top?
I think you probably could, give the latex about 30 days or so to cure. Don't see why you couldn't just use a water base poly though. I've had good luck with the MinWax version. The directions call for a minimum of 3 coats but on doors, tables and the like, I go 5.

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Old 08-30-2011, 03:30 PM   #3
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oil polyurethane over latex paint


I would use water based poly also.
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Old 08-30-2011, 05:49 PM   #4
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oil polyurethane over latex paint


Alkyd, or oil, poly will yellow/amber over time. Latex will not. I will respectfully disagree with Jschaben on wait times. You're fine to go once comfortably past the recoat time specified on the paint finish can. I say comfortably because sometimes dry times are longer in damper, cooler weather, an overnight dry should be sufficient. That said, if you start to see black tint appearing in your clear can, hold up and allow more dry time.
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Old 08-30-2011, 06:22 PM   #5
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oil polyurethane over latex paint


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Alkyd, or oil, poly will yellow/amber over time. Latex will not. I will respectfully disagree with Jschaben on wait times. You're fine to go once comfortably past the recoat time specified on the paint finish can. I say comfortably because sometimes dry times are longer in damper, cooler weather, an overnight dry should be sufficient. That said, if you start to see black tint appearing in your clear can, hold up and allow more dry time.
Agreed but I have never seen a polyurethane alkyd combination. An oil based marine varnish or one of the new silicone clear coats might work but will set you back a chunk.

I would not attempt a solvent based poly over water based paint especially with acrylic. If you use acrylic poly, as mentioned, just honor the recoat time. But you shouldn't set anything to heavy on the table until the acrylics cure. I set a glass show on gallery pedestals because we could not wait. All the tops had to be stripped as the weight just sunk into the surface-cured-only top coat. Under normal conditions semi gloss and gloss enamels cure in about a 30 day process.
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Old 08-30-2011, 07:25 PM   #6
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oil polyurethane over latex paint


Welcome to Alkyd Based Polyurethanes 101:
You should be aware that conventional alkyd based polyurethanes are simply alkyd resins exactly like you find in modern oil based paints that have been "modified" by adding bi- and tri- isocyanates to the pot when cooking up the alkyd resins. An isocyanate is anything with a -N=C=O group in it, so bi- and tri- isocyanates would have two and three of those groups in them, respectively.

http://www.********************/f13/...oil-base-8517/

Honestly, alkyd polys weren't exactly at the top of my mind, though I thought I'd heard of them before. I don't always get into the science of the products. I really just interchangeably used alkyd/oil in talking to a newbie. We both learned something.
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Old 08-30-2011, 07:32 PM   #7
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Thanks!
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Old 08-30-2011, 09:24 PM   #8
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oil polyurethane over latex paint


Sd, if you're interested in a science lesson on alkyd poly, I have that link bookmarked. Just noticed they blanked out most of it. I know the tech stuff floats your boat.
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Old 08-31-2011, 05:37 AM   #9
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oil polyurethane over latex paint


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Originally Posted by jsheridan View Post
Welcome to Alkyd Based Polyurethanes 101:
You should be aware that conventional alkyd based polyurethanes are simply alkyd resins exactly like you find in modern oil based paints that have been "modified" by adding bi- and tri- isocyanates to the pot when cooking up the alkyd resins. An isocyanate is anything with a -N=C=O group in it, so bi- and tri- isocyanates would have two and three of those groups in them, respectively.

http://www.********************/f13/...oil-base-8517/

Honestly, alkyd polys weren't exactly at the top of my mind, though I thought I'd heard of them before. I don't always get into the science of the products. I really just interchangeably used alkyd/oil in talking to a newbie. We both learned something.

Too deep for me

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