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Thread: waterbase poly over latex acrylic?

  1. #1

    waterbase poly over latex acrylic?

    Hello all!

    I'd like to know if it's OK to apply water base polyurethane over (100%) latex acrylic?

    I made a set of doll bunk beds for my granddaughter. She wanted a specific paint color that was only available in latex acrylic (rather than using an enamel), so I'd like to put a clear topcoat over it to give additional protection from dirt and fingerprints. I used a "premium" latex, but would like additional protection.

    Thanks for the advise!

    Cordially...John

  2. #2
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    I did a corner stand for a friend who wanted low/no cost. Planed construction lumber, left over wall paint and some Ace brand water based poly over it. So far so good, it hasn't debonded that I've noticed. By no definition is it fine furniture but it works for what they need.

  3. #3
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    Waterbased polyurethane is 100% latex acrylic. Acrylic paint is nothing more than water borne polyurethane and lots of pigment. Over coating will not provide any additional protection over that you get from the acrylic paint. Just add another coat of paint if you want more protection.
    Howie.........

  4. #4
    Hi Guy's,

    Thanks for taking the time to help! I guess I'll just add another coat of the latex paint then. I thought maybe the Poly might dry/cure harder than the paint giving better protection. Soooo, I guess I'll just wait an extra week or two before I give it to her to ensure the paint has cured well.

    Thanks again...John

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    Quote Originally Posted by Howard Acheson View Post
    Waterbased polyurethane is 100% latex acrylic. Acrylic paint is nothing more than water borne polyurethane and lots of pigment. Over coating will not provide any additional protection over that you get from the acrylic paint. Just add another coat of paint if you want more protection.
    Howard, that is not true in many cases. Many WB polys do, in fact, contain polyurethane resin and not just acrylic. I think some contain only polyurethane resins, but General Finishes has genericized their MSDS's to the extreme and now disclose nothing as to composition, so I can't offer an example as proof.

    John

  6. #6
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    I agree with you John; many of the water-borne "polys" are 95-99% acrylic and a small % poly resin...

    John Brady, a Gloss acrylic may help if you didn't use gloss for the paint. If you used gloss paint recoat it.

    FYI acrylics don't CURE, they are coalescing finishes.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  7. #7
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    Quote Originally Posted by Scott Holmes View Post
    I agree with you John; many of the water-borne "polys" are 95-99% acrylic and a small % poly resin...

    John Brady, a Gloss acrylic may help if you didn't use gloss for the paint. If you used gloss paint recoat it.

    FYI acrylics don't CURE, they are coalescing finishes.
    They don't cure? General Finishes seems to think they do: https://generalfinishes.com/professi...r#.VL28oy5Bn6F My own experience shows the hardness and chemical resistance increases after a week or two. To me, that suggests they cure.

    John

  8. #8
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    Indeed they do say that; if the crosslinker is added then it is a chemical "cure" that takes place. Generally speaking acrylics are coalescing finishes. Some Tech writers may very well call this curing.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  9. #9
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    Yeah,"curing".....it's like,if I bake a chocolate pie,how long do we wait before we cut it?

    Testing,in my pea brain trumps all.I have learned that speculation is limited by too many factors.Much easier...WAY easier,just shoot he panel/s and chuck them out the back door of the shop.Rain,shine...don't care.Leaving a finish sitting outside,cuts to the chase pretty durn quick.Not an accurate example of what you are trying to accomplish with your finish?Then come up with your own test.

    I'd say a CC in how you're proposing(as I understand the ?)would,add a very slight(am guessing because of the metric) amt of "protection".Admittedly a guess,comes from BC/CC in automotive applications.

  10. #10
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    Quote Originally Posted by john brady View Post
    Hi Guy's,

    Thanks for taking the time to help! I guess I'll just add another coat of the latex paint then. I thought maybe the Poly might dry/cure harder than the paint giving better protection. Soooo, I guess I'll just wait an extra week or two before I give it to her to ensure the paint has cured well.

    Thanks again...John
    While you are waiting the extra couple weeks why not paint a test piece with both the paint & the poly & compare the results to draw your own conclusion? Worst case? You could always strip & redo.

  11. #11
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    John Brady, it would be helpful to the discussion if you would reveal the specific latex paint you used.
    Scott Vroom

    I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.

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