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IndustryArena Forum > Material Technology > Material Machining Solutions > Treating cnc-carved MDF for concrete casting
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  1. #1
    Join Date
    Feb 2007
    Posts
    13

    Treating cnc-carved MDF for concrete casting

    I'm looking to cast a concrete tabletop with a particular pattern of deep, relatively wide grooves in the surface. The only cost effective material I know of in table-top sizes would be MDF, but it doesn't seem like it would be a very good choice for casting since it's so porous - especially the insides that would be exposed by cnc-carving. Is there any kind of mold-release that would work for MDF, and that wouldn't pool up in the grooves I'm carving? Or maybe there's some other kind of material available in large sheets that doesn't cost hundreds of dollars?

    Thanks!

  2. #2
    Join Date
    Jul 2005
    Posts
    12177
    Here is an idea, might work, might not.

    Saturate the surface of the MDF with melted wax. Melt the wax and brush it on after carving the shape. If it starts to solidify before it completely soaks in go over it with a hot air gun.

    It will certainly act as a mold release and it should waterproof the MDF for the time it will be in contact with the moisture in the concrete.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  3. #3
    Join Date
    Feb 2007
    Posts
    13
    Hey that's brilliant, thanks!

  4. #4
    Join Date
    Mar 2011
    Posts
    22
    Hi Geof,

    Was just wondering if spray painting MDF in oil based color will help in waterproofing the MDF. also, would a base coat be required for the same. Any idea on this one?? Thanks !!

  5. #5
    Join Date
    Jul 2005
    Posts
    12177
    In my experience nothing will seal MDF enough to have it exposed to water for more than a day or so. Oil based paints do soak in and give some protection but most paints once they are dry are slightly porous and as soon as a little moisture penetrates the MDF swells and then the paint cover gets cracked and very porous.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  6. #6
    Join Date
    Dec 2004
    Posts
    783
    Spar varnish works for me, I have an mdf panel coated in it that has been in the elements for years and it hasn't taken any water in, even on the exposed edges.

    Sent from tapatalk

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