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How to preserve and stabilize walnut knots and minor cracks

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  • How to preserve and stabilize walnut knots and minor cracks

    I just picked up around 35 board-feet of pretty clean and nice looking walnut for a shelf project. Each board has a few knots and/or great-looking "defects" in it. So I'd like to make them stable for cutting and finishing. In small stuff, in the past, I've used cyano and accelerator. I recall using epoxy a very long time ago and don't recall the results. The boards will be finished with a tung oil varnish mix then lacquer. That's going over an oil stain to get the color a little darker and more uniform. I got it to match our existing Wenge furniture in that room pretty well.

    I've never used a vacuum pump, and am not opposed to getting one and building localized "stick on" chambers for the knots and such.

  • #2
    I much prefer the cyano over epoxy for knot repair. I have to use it on nearly all of my Tiny Trees and mushrooms for knot and crack repairs. On boards, after the first rough sanding, I usually apply regular/thin ca and let it soak in. If it makes its way to the other side, as it normally does, I hit the back side with activator to stop the leak. After the knot is saturated I use medium then thick ca and activate to set it up. I have used the shop vac to pull epoxy through the knot, it worked fine but the whole process with ca only takes a few minutes and the finished results with ca was better. The ca is harder and sands to a glass finish.

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    • #3
      Does the CA stay water clear over time? I know that West System with fast catalyst turns yellow over time, but I don't think the slow hardener does. The yellowing can take a long time, like many months, or years, especially when exposed to sun light.
      When the makers of West System had a quarterly magazine, I subscribed for free when buying the pumps. There was a tip in one issue where the shop at West System jammed a bunch of those cheap disposable white bristle brushes into holes in a cardboard box with the bristle ends up. Then they mixed West System, thinned it with Lacquer thinner, and used a syringe to feed it into the ferrule of the brush. The idea was that it kept the bristles from coming out into the work product. I didn't know that epoxy would kick after being thinned.
      Another trick is to slightly heat the mixed liquid epoxy in a microwave just enough to start the cure. It sure doesn't take much microwave time to ruin a batch, though

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      • #4
        I don’t recall reading anywhere about ca yellowing. I haven’t had noticed any ca yellowing in the trees and tables I have that are 2 yrs old. Most of the wood fades/discolors in the sunlight in about that time. I keep West System II on hand for filling large cracks and holes that would take too much ca. Yesterday I filled a 1/4” crack with sys II and wood dust and black tint. When I mix too much dust in the epoxy it affects the cure. It never hardens rock hard, stays somewhat rubbery. Another brand of epoxy I have will absolutely not completely harden when I add color and glass fiber for thickener. It hardens to a semi hard tacky feel and then slowly over several weeks run out of the crack! I think that the speed it runs out of the crack depends on how valuable the furniture you have placed the Tiny Tree on!

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        • #5
          Some great practical advice, thanks! Sounds like I shouldn't even bother with vacuum either?

          The wife uses CA as her pen finish. It dries super hard, super glossy (she sands to 6000 then polishes), and no pen has ever changed color a decade plus later.

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          • #6
            Originally posted by capncarl View Post
            I don’t recall reading anywhere about ca yellowing. I haven’t had noticed any ca yellowing in the trees and tables I have that are 2 yrs old. Most of the wood fades/discolors in the sunlight in about that time. I keep West System II on hand for filling large cracks and holes that would take too much ca. Yesterday I filled a 1/4” crack with sys II and wood dust and black tint. When I mix too much dust in the epoxy it affects the cure. It never hardens rock hard, stays somewhat rubbery. Another brand of epoxy I have will absolutely not completely harden when I add color and glass fiber for thickener. It hardens to a semi hard tacky feel and then slowly over several weeks run out of the crack! I think that the speed it runs out of the crack depends on how valuable the furniture you have placed the Tiny Tree on!
            That's odd about not curing with pigments or fillers. I've used every type of filler that West offers, and pigmented many constructs with either West or Evercoat white pigments and never had the issues you mention. I've always mixed the epoxy and hardener, and then added thickeners and/or pigments as necessary.
            I do have some really old West System, and that just won't cure. Could that be the problem?

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            • #7
              My bad.... I mistakenly said the West System Epoxy wasn’t hardening properly, it is the other brand (can’t remember the name) that refused to completely harden when tinted or mixed with filler. I’ll update the brand name when I get back to the shop. The West epoxy does harden well but I have noticed that when I thicken it with wood flour dust it expands some. If I don’t give it but a couple of hours to completely expand and sand it smooth, 24 hours later you can feel each one of the cracks I have filled up, requiring me to resand the piece. This phenomenon prompted me to use CA for everything except the largest voids.

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