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Sealing MDO edges

Discussion in 'Materials' started by bayviewsignworks, Nov 30, 2012.

  1. We've tried 2 part wood "bondo", priming, painting, and using vinyl to close it it and water always seems to get in. Anyone have a foolproof way of doing it?
     
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  2. Gino

    Gino Premium Subscriber

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    Is your MDO pre-painted, primed or raw ??
     
  3. raw
     
  4. J Hill Designs

    J Hill Designs Major Contributor

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    paintable caulk rubbed along the edges and then wiped smooth before allowing to dry

    or

    wood glue applied in approximately the same fashion
     
  5. Thanks, I'm also reading that you shold take off the sharp edge as paint won't stick to a pointed edge. Just a slight sand to knock off the sharp edge.
     
  6. Pixels Are Bad Mmmkay?

    Pixels Are Bad Mmmkay? Very Active Member

    This is how we do it. Not saying it's the right way necessarily, but from all the tips I've picked up over the last few years it seems to be the general concensus.

    1) Cut the mdo to the desired shape.
    2) Route and sand edges, if necessary. I always like to route a radius all the way around both sides to help aid in water shedding.
    3) Fill any gaps in the plies with Plastic Wood putty, let dry and sand any high spots.
    4) Brush or use a rag to mop a good amount of Titebond II wood glue into the edges and allow to dry.
    5) Lightly sand, then do one more coat of Titebond II for good measure.
    6) Prime and let fully dry.
    7) Paint and let fully dry.
    8) Top coat and let fully dry.

    I wouldn't recommend using mdo for any type of long term signage unless it's floating between notched posts. If you run any kind of hardware through the wood or into the wood, it's most likely going to greatly compromise the life of the mdo. The moisture will find a way in, but can't get back out, rotting the wood from the inside out.
     
  7. Pixels Are Bad Mmmkay?

    Pixels Are Bad Mmmkay? Very Active Member

    Yes. It will shear away from the sharp corner, hence another good reason to always radius the edges.
     
  8. J Hill Designs

    J Hill Designs Major Contributor

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    Yeah, I dont go so far as to bull-nose it with a router, but a light sand to knock off the hard edge :thumb:
     
  9. Gino

    Gino Premium Subscriber

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    Kinda the same here.

    We fill all the voids in a series of steps, so as not to have a large clump of putty in there. We use Elmer's wood putty. Doesn't matter if its water based or not. Once it's completely dried, then we use our thumb and go up and down the entire edge with more putty on it. Let this thoroughly dry. Sand it and tack it. Make sure it's good and clean.

    Whatever you use first... whether it be prime or top coat, give the top two sides and all the edges a coat. A very thin coat. Almost like you're gonna push the roller through the surface to the other side. Let dry completely. Sand and tack again. Repeat the coating of all six surfaces. Let it dry completely and give it one last sanding and tack it off.

    Now, you give it another coat all around, but go slower and then in about 10 or 15 minutes... give it another rolling dry with the paint in the roller from before and go real slow, knocking out almost all of the bubbles.

    You'll have a glass looking finish and the edges should last for a very long time. Doing it this way, you won't see any of the plies along the edges, it will look totally flat.
     
  10. ChicagoGraphics

    ChicagoGraphics Major Contributor

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    Out of all the years we use MDO we never did anything to the sides, I have a sign hanging right next door that was put up 13 years ago and stilll looks new. I made on painted MDO
     
  11. john1

    john1 Guest

    I have done a few MDO signs and they all look good after being out a few years so far.

    Used elmers wood putty, sanded it down then painted the edges.
     
  12. Jillbeans

    Jillbeans Major Contributor

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    I usually use aluminum composite panels.
    But when dealing with MDO or plywood I use exterior wood putty to fill any holes, then Elmer''s Tite Bond 2 wood glue, then some KILZ primer. Sanding in between of course.
    Then I use an oil-based enamel paint as a final coat.
    Love....Jill
     
  13. Billct2

    Billct2 Major Contributor

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    I think the quality of the wood nowadays is so poor that it falls apart way too soon no matter what you do. I used to be able to make a sign out of AC plywood that would last longer than any MDO I try today. It seems like since it has the nice smooth face they can put any kind of garbage in bewteen. Of course there are different qualities of panels out there. The better sign grade or marine brands do work better.
    I keep asking my suppliers when are they going to come out with a .5" & .75" ACM. I think it would be a great product. I have used 6mm as a substitute on smaller signs. Even bonded two panels of 6mm together a few times.
     
  14. royster13

    royster13 Very Active Member

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    So how much time & materials is required to prep MDO to get it ready?....Versus just going with an aluminum composite material......
     
  15. Gino

    Gino Premium Subscriber

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    With paint and labor, it's less expensive to use the composite aluminum, but there are those times when 1/2" or 3/4" can't be beat.

    It's good to be able to use what you want to make the job easier or less expensive, but it's another thing to know how to at least use all the substrates at your finger tips.
     
  16. BrianKE

    BrianKE Member

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    Surprised no one has mentioned plastic edge cap. Granted it will only work on straight or slightly curved edges but edge cap will seal the edges as well as give a nice frame to the board.

    The edge cap needs to be notched to a 45 angle at each corner (tool for that is available form anyone that sells the edge cap). Before applying the edge cap I apply a bead of caulk to the inside of the edge cap and then put the edge cap on the board. Tap lightly all around with a rubber mallet and you board is sealed up tight.

    This process is much simpler than painting, puttying, bondo-ing, etc.

    I think the edge cap also comes in a variety of colors should you want that.
     
  17. BrianKE

    BrianKE Member

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    Why not use pre-painted boards? I know raw are slightly cheaper but a lot of labor going into painting the board to finish it.
     
  18. Gino

    Gino Premium Subscriber

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    Reason we don't use pre-painted is..... none of your putties or primers will stick worth a sh!t to it.
     
  19. Baz

    Baz Very Active Member

    Pre-painted finish just plain sucks. And the paint peels off after 2-3 years ... So why even bother filling in the edges?

    If you are using MDO ... Raw is the way to go.

    Also .. 95% of the MDO i use is for construction companies and rental signs. I don't bother with the edges and the signs last up to 8 years or so .. Even for those signs i am starting to use Dibond more and more just to save on the painting and sanding steps.

    Only "nice/special" projects will i fill in the gaps with wood filler, take off the sharp edges and put on two coats of primer before two coats of enamel with a light sanding in between coats.
     
  20. john1

    john1 Guest

    The few ones i have done i used the RTG ready to go and it is holding up fine.
     
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