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Thread: Fill cracks in 100 year old oak beam now mantel

  1. #1
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    Fill cracks in 100 year old oak beam now mantel

    I making two fireplace mantels out of a 100 year old white oak beam. Wife wants the cracks filled. Should I do black, brown, or clear? I am very uncertain. There are large wood borer holes and other defects and I plan to leave them unfilled. Also I would like to wire brush before a "Flater than Flat" finish. Worried about how the wire brush will scratch the fill. Maybe I can't wire brush.

  2. #2
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    I think that the answer to your question comes down to what you plan for your overall finish look when completed and whether or not you want to highlight those defects with the resin (contrasting color value) or make them disappear by coloring the resin to be close to the finished hue you plan for the mantle post-finishing. This is 100% subjective.
    --

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  3. #3
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    I've only done clear before. Thinking dark brown might be good

  4. #4
    Wood turners are always filling voids. Ground coffee in epoxy makes a good fill that looks kind of "bark-ish". Natural color, has some visual texture, doesn't look so "plastic." Use dry coffee, not wet grounds (some folks are so frugal they'll only use used grounds -- if you're one of them, they have to be dried before use). I have a burr grinder that can be set for different grinds -- when I have some coffee beans that get old enough I don't want to drink the coffee from them, I grind them into different particle sizes and put them in old plastic sour cream tubs marked by size (relative). They get soaked through by the epoxy and machine pretty much like epoxy.

    Another option is chunks of bark that you crumble in a spice chopper or food processor (this is not necessarily a "friendly" use of those tools). If you want something closer in color to the original wood, you can use sanding dust from the same wood (though dust of the same wood will appear darker as a fill than the intact wood -- it's basically end grain and darkens more). Wood flour is commecially available. A pound (which is a lot) is like $4 from raka.com. From the smell, I think the flour I've gotten from Raka is red oak.

    Epoxy can be tinted to help get the color you want. Most anything can be used to color fills that aren't structural. I have Transtint dyes in the shop for other reasons, they work well. If I'm trying to hide something in cherry, I'll use wood flour with some Transtint reddish brown. Remember that when trying to "match" patches, missing the color on the too dark side is way better than missing the color to the light side. Also remember that you're trying to match the color after the wood is finished and aged (many woods darken with age). Epoxy fills won't darken appreciably when you cover them with finish the way raw wood does. Another reason to err on the dark side.

    Epoxy fills usually shrink as they cure. I don't know for sure, but I think this is not so much true shrinkage as it is that some of the epoxy soaks into the wood and is lost from the void. Overfill the voids, or plan for two additions. Not a huge deal with non-structural applications, but cured epoxy is covered with "amine blush" that keeps the next application from bonding well. Avoid this by making your second fill before the first is fully hardened.

    Abraided epoxy gets a white cast to it from the fractured surface. You can quiet that with some Danish oil, shellac, or some other finish painted onto the epoxy only. Shellac is nice because virtually all finishes adhere well to it.

    Experiment on scraps!

    Best,

    Dave

  5. #5
    depends on what the room looks like...crushed turquoise, or a green gem color to match any pillows or secondary colors in the room? If you have a partner, ask them what they think?
    Be the kind of woman that when your feet hit the ground each morning, the devil says, "oh crap she's up!"


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  6. #6
    Depending how deep you may want to do 2 pours. Tint the first, then do clear for the second. You might be able to wire brush between pours. If the wire brushing is final step before finishing (not sanding) then I would mix in sawdust to create more of a paste. Let cure and then brush, should reduce scratches.

  7. #7
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    My go-to filler for a lot of cracks and small defects is thick cyanoacrylate mixed with dust from my sanders. I keep a few plastic jars around with different tints. Dye powder works well - I bet even RIT dye would work. I go for darker contrasting colors and in most woods, they end up looking like mineral streaks or rays in the grain.

    The dust will cause the glue to activate after 30-60 seconds, so I just mix a bit at a time on a piece of paper with a little "spatula" of thin wood and smear it into the cracks until it hardens or I run out. It sands well and polishes out better than epoxy, IME. As always, test it before committing...
    JR

  8. #8
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    Joe
    I read a thread by Michael Dresdner many year ago about filling cracks. His position is that trying to "match" it, will only partially work, and you'll never successfully hide the defect, so don't try. Use the cracks as part of the design. He just fills with a black epoxy.
    I also like Michelle's idea. With the popularity of "River Tables", there are a lot of nice options for really making those cracks and splits into something special.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  9. #9
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    Pillows, etc. are easy to change as tastes and styles change. Mantle less so. Think about something that future owners will be able to work with as styles and tastes change.

  10. #10
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    Quote Originally Posted by Nicholas Lawrence View Post
    Pillows, etc. are easy to change as tastes and styles change. Mantle less so. Think about something that future owners will be able to work with as styles and tastes change.
    Luckily this is the last house we expect to own so we are doing it for our tastes. That said, the design and materials of the home itself are intended to be timeless. Like a old house with very traditional casing, trim, wainscoting and stone and wood that are fitting that style. The furniture and lighting are where the home takes character.

  11. #11
    Join Date
    Apr 2017
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    Patch the cracks with matching Oak. Whittle pieces to be pounded and glued into them then trimmed flush. This works pretty well.

  12. #12
    Join Date
    Oct 2007
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    New Hill, NC
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    IMO, black epoxy in white oak is like a black cocktail dress - it never goes out of style (especially when combined with an oil finish).

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