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Thread: Waterproof MDF?

  1. #1

    Waterproof MDF?

    Has anyone here ever used it?
    What should I know if I want to use it for signs?

  2. #2
    Join Date
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    OSB. Outdoor Sign Board. It's a different construction than MDF.
    Never, under any circumstances, combine a sleeping pill, and laxative on the same night.

  3. #3
    Quote Originally Posted by Myk Rian View Post
    OSB. Outdoor Sign Board. It's a different construction than MDF.
    As far as I know OSB is "oriented strand board"

    Extira is a good choice for signs
    LRG WoodCrafting (Google it )

  4. #4

    http://www.signfoam.com/

    Extira is a good choice as well as Sign Foam

    both do well outdoors in the elements but Sign Foam is specifically made for sign making. it machines well with regular carbide tooling and takes a finish too.
    S.M.Titmas.

    "...I had field experience, a vocabulary and a criminal mind, I was a danger to myself and others."

    -Anthony Bourdain

  5. #5
    Look into MDO or Medium Density Overlay.

    It's exterior grade plywood with an "MDF-ish" top veneer so it paints up nice, but is suited for outdoor use.

    If you ever consider MDF for outdoor use, try the test I did: leave a piece of MDF out in the elements for a month. My test piece expanded to TWICE it's original thickness. I don't think any amount of waterproofing will prevent it from expanding significantly.

    I'm sure someone around here's done it with great results, but I personally wouldn't risk it when there are other better plywood-based options.

  6. #6

    I know I can get Extira in a lumber yard.

    So, where do I get Sign Foam?

  7. #7
    Quote Originally Posted by Tony Bilello View Post
    So, where do I get Sign Foam?
    tony,
    do a Google search for distributors in your area.

    shawn,
    mdf is NOT rated for exterior use.
    mdo and mdx are rated for exterior use and can be cut and machined with no loss of waterproofedness.
    exteria is a different composition than the md's and is specific for exterior use
    Last edited by sean m. titmas; 06-07-2009 at 1:00 AM.
    S.M.Titmas.

    "...I had field experience, a vocabulary and a criminal mind, I was a danger to myself and others."

    -Anthony Bourdain

  8. #8
    Join Date
    Dec 2008
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    Northern Michigan
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    Tony, I have MDF signs that have been outside for around 18 years that are still just fine, and our weather here is not kind to, well, anything. I cut and shaped the letters and then treated with a couple of coats of West System epoxy, and then painted with Imron over adhesion promoter used for urethane bumpers.

  9. #9
    Plum creek is a good name in mdf for interior use. medex is one that is designed for exterior use. It uses different resins and is rated for exterior use.
    Steve Jenkins, McKinney, TX. 469 742-9694
    Always use the word "impossible" with extreme caution

  10. #10
    Join Date
    Jul 2005
    Location
    Sammamish, WA
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    MDO is so waterproof that the highway department uses it for their signs with no finish at all on the back and it lasts for many years. It is, however, about $30/sheet more than MDF. I have not tried MDF for signs, but have laser cut lettering with it that were mounted outdoors and had good results. I used a shellac based primer and two coats of paint on the front, back and edges.

    If budget is a big consideration I might try it for signs that are at least under an overhang so they will not be sitting in water, otherwise I'd use painted MDO. The sign supply will have it plain, primed, or painted. Here we have several and one will even CNC cut it to size and shape and add T-molding if desired.



    Sammamish, WA

    Epilog Legend 24TT 45W, had a sign business for 17 years, now just doing laser work on the side.

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  11. #11
    Join Date
    Mar 2009
    Location
    Co Roscommon, Ireland
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    Extira Equivilant??

    Quote Originally Posted by Leo Graywacz View Post
    As far as I know OSB is "oriented strand board"

    Extira is a good choice for signs
    Hey Guys,

    Just wondered if anyone knows if there is an equivilant to "Extira" available in Ireland/UK or even Europe??

    I did send an email to Extira and they don't have distributors in Europe.

    "The only thing we can do is ship full containers.... " well I don't think I actually want a "full" container.

    Anyone have any suggestions? It's a shame as it looks quite good judging from the photo's on their website.

    Thanks
    Karen
    One in four people are unbalanced. Think of 3 friends, if they seem OK; you're the one

    LS6040PRO, LaserCut 5.1, CorelDraw X4, Photograv 3

  12. #12
    Join Date
    Feb 2003
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    Dallas, Tx.
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    Quote Originally Posted by Tony Bilello View Post
    So, where do I get Sign Foam?
    When you find the cost of SignFoam, you may be surprised. I've used it for many years, but the last time I purchased a 3/4" 4x8 was several months ago. I think it was $90. I've bought it up to 3" thick, about $350. It is extremely porus and to get a slick finish youl'll have to use a product from Coastal Products to fill it. But it has some neat properties for outdoor use.
    Phil in Big D
    The only difference between a taxidermist and the taxman, is that the taxidermist leaves the skin. Mark Twain

  13. #13
    Join Date
    Oct 2008
    Location
    Webster Groves, MO
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    Quote Originally Posted by Karen Thompson View Post
    Hey Guys,

    Just wondered if anyone knows if there is an equivilant to "Extira" available in Ireland/UK or even Europe??

    I did send an email to Extira and they don't have distributors in Europe.

    "The only thing we can do is ship full containers.... " well I don't think I actually want a "full" container.

    Anyone have any suggestions? It's a shame as it looks quite good judging from the photo's on their website.

    Thanks
    Karen

    I just happened upon this thread looking for a stable substrate for veneering (still don't trust MDF). My brother-in-law is running an archeological dig in Roscommon ( Kilteasheen I think) again this summer and will probably be flying back and forth to St. Louis a few more times. Want me to see if he can fit a 4' x 8' sheet in his carry-on luggage?

  14. #14
    Join Date
    Mar 2009
    Location
    Co Roscommon, Ireland
    Posts
    57

    Thumbs up

    Quote Originally Posted by Stephen Musial View Post
    I just happened upon this thread looking for a stable substrate for veneering (still don't trust MDF). My brother-in-law is running an archeological dig in Roscommon ( Kilteasheen I think) again this summer and will probably be flying back and forth to St. Louis a few more times. Want me to see if he can fit a 4' x 8' sheet in his carry-on luggage?
    oooooh yes please - that's only down the road from me - I can pick it up
    One in four people are unbalanced. Think of 3 friends, if they seem OK; you're the one

    LS6040PRO, LaserCut 5.1, CorelDraw X4, Photograv 3

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