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Thread: Polyurethane (what am I doing wrong)

  1. #1
    Join Date
    Mar 2009
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    Leominster Mass
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    Polyurethane (what am I doing wrong)

    I am using a water based Poly since the oil based has such a strong smell and my wife is very sensitive to this.
    When I apply the poly I get tiny air bubbles so it is not as smooth as I would like it to be.
    I am using cheap foam brushes, could this be the reason? Maybe using a quality brush would make a difference? Is there any tricks that would help?

    Thanks
    Dan
    Dan Thibert
    Leominster MA

  2. #2
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    May 2007
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    Kansas City, Missouri
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    I haven't used it a lot, but what kind of wood are you applying it over?

    Could be the pores in the wood, might need filling or will correct on a later coat.
    Could be the room tempature.
    Make sure your only brushing over in one direction and not rebrushing.
    I've also had good luck using a terry cloth towel or piece of it and doing light coats.

    just my .02
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  3. #3
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    Wood is red Oak, and I am usually brushing with the grain but not always

    Room temp is about 60 to 65 degrees, my basement does not have heat.

    How do you fill pores of wood?

    Thanks for your help
    Dan Thibert
    Leominster MA

  4. #4
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    Billings Missouri near Springfield Mo
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    Also never shake a can of waterbase anything it will cause air-bubbles in the finish

  5. #5
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    Nov 2006
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    Delton, Michigan
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    red oak is one of the worst for bubble because of the porous grain.. after a few coats you can seal it.. or you can try seal coat from bulls eye products first its a shellac based product and give it two coats first then touch sanded before your top coat. and dont over brush it like darren said.
    If in Doubt, Build it Stout!
    One hand washes the other!
    Don't put off today till tomorrow!

  6. #6
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    Quote Originally Posted by larry merlau View Post
    and dont over brush it like darren said.
    I'm not sure if I'm doing it right or wrong now?
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  7. #7
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    Quote Originally Posted by Darren Wright View Post
    I'm not sure if I'm doing it right or wrong now?
    hey if yu can get it to go your way its right darren i am not no pro just voicun my methode.. and i had troube with bubbles too in the beginng. dust ,raised grain. but i do like shellac for wash coat now pops the figure and make life better for me. used to use min wax wipe on poly all the time and like it as well.
    If in Doubt, Build it Stout!
    One hand washes the other!
    Don't put off today till tomorrow!

  8. #8
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    Nov 2006
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    London, Ontario
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    Hey Dan, some good advice here.

    I just went digging and found this... I wrote this a couple years ago on another forum, and it pretty much covers how I brush on WB poly:

    ----------

    I have been using Flecto Varathane WB clear finish on my projects for 10 years and never had any dissatisfaction with it. Granted, I am a hobbyest, not a pro, so 10 years isn't a huge number of projects. But the fact remains, the product is fine.

    I tend to always use a foam brush. And like has been mentioned, you must NOT try to "work" the finish. Dip the brush, hold it over the can, letting the excess drip out (do NOT wipe on the edge of the can, that makes it foam up), and then spread it on the project. You can go back over the finish MAYBE once, to make sure it is spread out, but that is it. You cannot keep working it.

    Make sure your area is well lit with angled lights, so you can see the "dampness" of the finish, to ensure that you cover all the areas. I find I lean over a lot as I apply it, to ensure that I see it is covered.

    The first coat is always the worst. The wood sucks it in, and it takes forever. It also raises the grain and feels rough. So after the first coat, I go over the project with some 220 grit paper wrapped around a sanding block. One or two light passes and it will feel much smoother.

    Then again, with a second coat, another extremely light sanding inbetween - use worn 220grit, just lighly touching here or there where you feel roughness.
    Usually a third coat also. You'll find that the 2nd and 3rd coat go much quicker, as you can spread out the finish much further.

    Yes, there often appear to be lots of bubbles... I have had to train myself to mostly ignore them. They level out on their own and go away as part of the drying process.

    Finally, after the 3rd coat, I'll dribble on a little water -- just a few drops -- and polish it up with a synthetic #0000 3M pad.

    ...art

    ps: my shop is in my basement, so it is in conditioned space, warm in winter, cool in summer.

    ----------

    in addition, Like Larry said, red oak with the pores is tough. I almost never use red oak, so I did not mention it above. A few months ago I did make a shelf with red oak and I wish I had used a sealer on it, I had 5 coats on it and it still was not as level as I'd like.
    There's usually more than one way to do it...
    www.wordsnwood.com ........ facebook.com/wordsnwood

  9. #9
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    Mar 2009
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    Leominster Mass
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    Great info Art,
    OK lets see if I got it

    mistake #1 used red oak
    mistake #2 wiped brush on side of can to get excess out
    mistake #3 brushed multiple times in order to get full coverage

    Did I miss anything

    So what is the best wood for a new woodworker like myself? I have used Poplar as a soft wood and I have used Maple as a hard wood.

    I do not feel so stupid knowing I am not the first

    When I am finished this little box that has throughly kicked my behind I will post a picture. It is nothing like the work I see here, but there is a lot of time into it, not to mention a lot of wood redoing the stupid top so it would fit
    Dan Thibert
    Leominster MA

  10. #10
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    Mar 2009
    Location
    Leominster Mass
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    WOW what a difference a little knowledge makes

    I just got home and put another coat of Poly on my little box. I did not put the brush up to the side of the can, instead held it over the can till it stopped dripping. Then I only applied the brush to the wood in one stroke. It was thinker than I have been getting and smooth.

    I think this is going to work

    Thanks for all your help
    Dan Thibert
    Leominster MA

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