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Thread: Polycrylic durability?

  1. #1
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    Polycrylic durability?

    I like the Minwax Polycrylic. It's clear and doesn't yellow. It dries to the touch in 15 minutes and can be recoated in 2 hours. It's low-odor and water cleanup.

    Three or four coats give a good build. My wife says women like stuff to be shiny, and the gloss polycrylic is nice and shiny.

    The biggest downside I've seen is the difficulty with brushmarks, and I've been thinking about trying out the foam brushes. Have you had experience with that?

    I've gotten the impression that it might not be as durable as the solvent-based polyurethane. (Of course the latter will turn yellow with time.)

    Has anyone seen durability issues with the polycrylic?

    While we're on the subject, I'm thinking I should sand the raised grain after the first coat of polycrylic. Maybe with 320 or 400 grit? That seems less of a problem when I first apply a washcoat of 1# blonde shellac.

    Tried to wipe on polycrylic, with and without diluting it with water. That didn't work out too well for me.

    Don't see much point in sanding between coats, do you?

    What would you think about building 2-4 brushed coats of polycrylic, letting it cure for a day or two, sanding lightly with 320 or 400 grit, then applying a final coat:
    1) very thin coat with brush;
    2) very thin coat with foam brush; or
    3) spray/aerosol final coat.

    Appreciate your thoughts and hearing of your experiences.

    Fred
    If I'm gonna mess up this bowl, please, let it happen BEFORE I sand it!

  2. #2
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    Minwax Polycrylic

    i have only used it three times, twice on bleached box elder and once on magnolia

    Minwax Polycrylic is water based and will not yellow the wood

    i talked to representative and he said it should hold about 20 years without yellowing

    i put on three coats, fisrt coat wait 2 hours sand very lightly with 220 grit, apply next coat, wait 2 hours, sand with 220, apply next coat the sanding in between is so the poly can bond between coats

    when i apply a coat it is very lightly(try very lightly, i have to go back and take out drip marks if i get too much on it), i use a timer and at 10 minute intervals i come back and brush out any drip marks, the most i have had to come back is 3 times

    after 1 month, (i think 2 weeks would do it) sand lightly with 1200 grit and wipe down great stuff

    there are 3 types, semi, gloss, and satin you can put whichever one you like on last and that will be the way it comes out i used the semi with 3 coats and then i wanted a higher gloss and put one coat of gloss on over top and it came out great

    mike if you read this i know i gave you are hard time about shiny finishes but certain woods call for a shinny finish
    Last edited by charlie knighton; 06-26-2008 at 4:57 AM.

  3. #3
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    Sanding between coats is sometimes a concern when better adhesion is required but this is not the case. You sand after the first coat because water is absorbed by the woods fibers and makes them stand up. This is almost gone after the second coat but now the function of light sanding (with fine paper) is mainly to remove small bumps resulting from dust, punctured bubbles, etc.
    Perfect glossy coatings usually demand drying in a dust free environment (mop floor with wet cloth, close doors and windows until fully dry,... the works)

  4. #4
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    I used the spray on version of this on a Morris chair I built. It is holding up very well. Use to us it all the time on RC sailplanes. Strengthen the wood and was lighter than the oil based stuff.

  5. #5
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    Polycrylic is basically an acrylic finish with a little polyurethane resin added. Like almost any other film finish you can use, there are no really "durability" concerns with the product, especially on a turning. But IMHO, turnings are often better served by oil finishes simply because of what they add to the wood. For those times when you specifically want to minimize color shift, a water borne finish can have benefits. The only "benefit" with Polycrylic over other water bornes is availability, frankly. You can buy it at any home center for the most part.

    BTW, a polyurethane is probably not the best finish for a turning simply because poly was designed for abrasion resistance and therefore, you cannot buff it out as nicely (buffing is abrasion) as you can a non-poly varnish. Water borne poly isn't really anything like an oil based poly since it's an acrylic, but the same comment applies to the buffing. Poly was designed for floors...
    Last edited by Jim Becker; 06-26-2008 at 10:51 AM.
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  6. #6
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    I aggree with Jim hard to buff, it does not with stand heat from a buffer well. Not the most perfect finish I usally have bubble issues and weh nperfect never looks 100% clear. To get waterbase poly right it is really made to float a finish like on a floor you can't do that on a turning that is why you are getting brush marks it is not think enought to flow.

    Anyohow like you I used the stuff for years finally tried some laquire finishes with a HVLP gun. Much better. I would sugest maybe reading a bit more on some finishes and trying some hand rubbed finishes. Tung oil is nice but does take more time to dry. There got to be something else out there maybe someone else will chime in.
    -=Jason=-

  7. #7
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    Wink

    If I load the brush lightly, then go around the bowl tipping off, the brushmarks are minimized. If I don't overbrush the finish, it will level pretty well - and the instructions on the can do caution against overbrushing.

    That said, I've never gotten the completely smooth finish, free of brushmarks, like one can get with a spray. Some day I'll have an HVLP and use the lacquer (or save $800 and try the spray cans of lacquer ) ... or maybe try brushing 2-3 coats and then using the aerosol for the final coat.

    As I mentioned, SWMBO likes the shiny finishes and doesn't like the color added by BLO or oil-based poly.

    When I (eventually) get a buffing system, like the Beale, I'll probably be more interested in the oil finishes. Until then, the polycrylic gives a good shine without much work.

    Norm, the way I understand it (from Flexner's writing?) is that sanding between coats (after the first coat) improves adhesion of solvent-based poly ONLY IF the previous coat has been allowed to cure (cross-link) and must then be roughened. I was thinking there's a 'window' between coats (4-12 hours? 4-24 hours?) when the sanding isn't needed. Is that wrong? (And does the same apply to waterbased?)

    Jason, I have BLO, Walnut oil, and Tung Oil. My impression is that the BLO may cure harder but takes longer, and that the walnut oil takes longer to cure than the tung oil. For maple I like the mineral oil or butcher block oil, but I don't think it hardens. Would you agree?
    If I'm gonna mess up this bowl, please, let it happen BEFORE I sand it!

  8. #8
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    Brush vs foamy????

    I use the foam. It minimizes brush marks, etc.
    Bob

  9. #9
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    Bump...

    So which cures hardest: Tung Oil, Walnut Oil, BLO ?

    How long do you wait between coats?

    How long before you buff?

    Thanks, Bob. I'm gonna try the foam.

    Fred

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