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Old 03-05-2012, 07:04 PM   #1
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poly over acrylic paint, possible?


People,

is it OK to coat some artistic design, painted with acrylic on a wall, with polyurethane oil base? Just want to get a nice shine /protect it some.

Thanks!

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Old 03-05-2012, 07:13 PM   #2
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poly over acrylic paint, possible?


No. The oil will immediately yellow it , and it will get worse over time.
I would use an acrylic clear- they wont yellow- but are a bit hard to handle because they dry so quick.
Another think I have done is get a qt of waterbase glazing, mix 1/1 with water and basically wash the area with that. let dry - do again.
Only if what you are covering won't be lifted with a washing though.

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Old 03-05-2012, 07:16 PM   #3
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poly over acrylic paint, possible?


You do not want, unless you have too, put an oil clear coat over latex.
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Old 03-05-2012, 07:32 PM   #4
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poly over acrylic paint, possible?


ok, thanks. Clear water base is it. The lifting part- thats why I posted here- how can an oil base lift dry/cured acrylic? Dont think its possible. Still, I believe your opinion on water base is right.No yellowing. But I coated a floor with water base years ago (Bona), man, you gotta work fast with that stuff.
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Old 03-05-2012, 08:41 PM   #5
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poly over acrylic paint, possible?


It is doubtful that the WB clear will do any lifting either if its dry and cured.
We repaint over the stuff within hours usually.
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Old 03-05-2012, 08:45 PM   #6
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poly over acrylic paint, possible?


The oil won't lift it, but the latex may. If you do the clear after 7-10 days you should be okay with not lifting. If the acrylic isn't cured, the latex may reactivate it. You'll see some color building in your clear brush.
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Old 03-05-2012, 08:48 PM   #7
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poly over acrylic paint, possible?


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It is doubtful that the WB clear will do any lifting either if its dry and cured.
We repaint over the stuff within hours usually.
That's right. Usually you only need to get past the recoat time of the finish to apply the clear. Depends mostly I guess on what you're going over. I erred on the side of caution.
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Old 03-05-2012, 09:25 PM   #8
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poly over acrylic paint, possible?


Oil and water can mix but you should not try to make it happen unless we are talking about light salad dressing or lava lamps, always iconographic and of course the real ones were made in Chicago. I give the USB ones to college kids. And they become smarter.

http://www.lavalamp.com/


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Old 03-05-2012, 10:45 PM   #9
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poly over acrylic paint, possible?


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People,

is it OK to coat some artistic design, painted with acrylic on a wall, with polyurethane oil base? Just want to get a nice shine /protect it some.

Thanks!
Hey Noquacks,

The answer to your question is "yes". It is perfectly OK to put an oil based poly over an acrylic paint - maybe not the best thing to use in your case, but there'll be no incompatibility between the 2 resin types. Brush Jockey gave the best reason not to use the oil - it'll yellow. It's more amber (than acrylic) to begin with and it'll get more yellow over time (nature of the beast). Only you can answer whether the yellowing would be a benefit, or detriment, to the artistic design. If it is a concern, then a clear acrylic, a clear acrylic poly, or a water-borne poly (not acrylic nor alkyd modified - a true urethane coating coating, borne in water, often times used for gymnasium floor finishes and usually/sometimes requires a hardener) would be a better choice.

I want to address some of the other comments on here regarding mixing of these 2 resin types...Several years ago, to suggest that oils/alkyds could not be used in conjunction with latex coatings was more true than it is today. But even then, it had more to do with each resin's adhesive characteristics and drying mechanisms than it did with any incompatibility of resin types. From a manufacturing perspective, it is still a generally accepted notion to not create a system that includes a restrictive, rigid coating (alkyd) over a more malleable, flexible coating (latex) when applied over an unstable substrate (wood) - but even with that particular caveat, it's not because of an incompatibility with the resin types, it's because the rigid coating can't expand at the same rate that the latex coating AND substrate will.

In terms of the oil and water thing goes, those are true statements as they relate to lava lamps and salad dressings, but the truth is emulsifiers make these two opposites actually kind of not-so-opposites anymore. Driveway sealers are emulsified oils and that technology has been around for decades (and decades)...Our friends in Europe still regard latex products as "Emulsion Coatings". I mean, you all are aware that pretty much all latex resins (Acrylics, PVA, Vinyls, etc.) ARE actually petrochemical processes, right? ...and that acrylics and vinyls both are delivered to the market in water-borne and solvent-borne offerings? Same is true for alkyds - they're now available to the DIYers in a water-borne format (again, this technology has been around for years, only recently has their been a place in the market for the small pot 'n' brush guy or the homeowner)...It's interesting 'cause typical alkyds (oil based coatings) are actually more of a "natural" product than are their latex counterparts...

Aside from all that non-sensical paint trivia, probably the most common misnomer of the incompatibility of the oil/water issue (as it relates to paint, at least) is this; both the resin types (oil/alkyd and latex, be it acrylic, vinyl, whatever...) are reactive films. They dry/cure by means other than just solvent evaporation - once cured, they are no longer dissolvable by the solvents that delivered them to the project and can really no longer be regarded as an oil or water based anything - at least from the perspective of containing either oils (non-drying) or water, so an incompatibility based on the whole water and oil argument is really no longer valid anyway.

So, even though it is true that each resin type has their own distinct advantages and disadvantages, incompatibility between the 2 are not really a disadvantage for either. ...sorry for the boring, tedious rant - I must be in one of those moods to hear myself wax somewhat eloquently again.

Disclaimer: Please, no disrespect is intended to anyone who has had experiences that would seem inconsistent with the things I've said here tonight. If a person is not comfortable using a latex and an oil (alkyd) within the same scheme, then don't use that system. In this goofy, inexact science of what we call painting, there are many more ways than - 1 - to properly and successfully paint a surface.

Last edited by ric knows paint; 03-06-2012 at 09:04 AM.
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Old 03-06-2012, 03:48 PM   #10
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poly over acrylic paint, possible?


I have had the yellowing experience but it actually looked pretty good with the overall coloring scheme.
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Old 03-07-2012, 05:19 PM   #11
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poly over acrylic paint, possible?


If you decide on a WB polyurethane, test a small area first. All polyurethane resin has an amber cast. The WB is less than oil and will not further yellow with age,

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