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Thread: Black Walnut Slab - PLEASE HELP!

  1. #1

    Black Walnut Slab - PLEASE HELP!

    Hi. I am a complete beginner when it comes to woodworking. I bought a black walnut slab almost a year ago and it has been haunting me ever since. This slab is meant to become a free standing countertop/long table.

    Upon arrival I began sanding it beginning with coarse grits, working all the way up to 320. I decided I wanted to keep the bark on to keep the color contrast. Controversial I know, especially because even from the beginning I noticed small potato-bug-like beetles ending up on the ground beneath the slab accompanied by small piles of sawdust. I sanded the top and bottom probably to 180 before I filled some cracks, holes, and crevices with epoxy, the west systems stuff. By the way this is over the coarse of up to 5 months at this point, I ran into many issues and wasn't sure how to solve them so this slab stayed idle for weeks at a time sometimes. Over the winter it remained in my attic, I sanded a few times, and also began smoothing out the bark on the sides.

    Throughout this whole time, holes would pop up from those critters, mainly at the joining of the bark and the wood, although since then small holes have shown up elsewhere in the wood. I finally decided to just finish it in the hopes of suffocating the bugs.

    After sanding to 320 I decided to poly it using a water-based Miniwax polyurethane (polycrilic), clear satin. I didn't want to use stain of any sort as I only wanted to bring out the natural color of the walnut. I've put on between 5 and 10 coats on both sides, sanding lightly between every few coats until I began using a special water-specific applicator which left it smooth enough.

    Holes! More holes kept appearing, so I injected the poly into them if they were large enough, some on the bark, some on on the wood surface. Since then it has stood idle for a week or so, then another coat or 2, then more holes, and this process keeps repeating.

    Sorry for the length, it's been about a year and I wanted to detail the process so I could get some specific advice. I need the bugs to die since they keep affecting my finishing process. Once they are gone, a few more coats to fix it up and I'll be set.

    Also, at some points during the finishing process poly has dripped onto the top side, creating small bumps of extra poly. These, I've found, are difficult to sand out, and sanding affects the the surrounding area, scratching it up when I only intend to get rid of the bumps. Any advice here?

    Eventually I plan on drilling holes in the underside for 3-4 hairpin legs.

    Pictures of the slab, and examples of holes and rough patches attached. Having trouble attaching all of them, more to come.

    Thanks for any advice and insight!
    Attached Images Attached Images

  2. #2
    Join Date
    May 2007
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    Well, with it being sealed, I'd say heating it to kill the powder post beetles is probably not going to work, (without damaging the finish, anyway). I'd find someone with a walk-in freezer that gets well below 0 degrees F. I'd leave it in there as long as you can stand it. That should do the trick.

    Dan

  3. #3
    Join Date
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    Quote Originally Posted by Matthew Gelb View Post
    Throughout this whole time, holes would pop up from those critters, mainly at the joining of the bark and the wood, although since then small holes have shown up elsewhere in the wood. I finally decided to just finish it in the hopes of suffocating the bugs.
    Are the holes tiny, 1/8" or smaller? If so, look up "powder post beetles" (there are several different varieties). They mostly get into wood that is not dry and can live in the wood for a long time. Here is one article: https://www.doyourownpestcontrol.com...ostbeetles.htm

    You can't usually get rid of them by putting something in the holes. There are things you can do to prevent a board from being infested, but the best thing to kill them in the wood might be to heat and dry the board. Some people will get it heated/dried in a kiln. I've heard of people wrapping the wood in plastic and setting it in the sun but I've never tried that. The article mentioned above indicates some pest control companies can fumigate the wood. If I have wood with PPBs I usually get rid of the wood, but most of mine is smaller turning stock, not a large slab.

    BTW, someone gave me some 2x2 walnut turning squares once and I put them on a shelf in the shop. One day I heard a faint "scritch, scritch, scritch" and looked just in time to see a PPB chew its way out of the wood! What are the chances?!

    JKJ

  4. #4
    Join Date
    Oct 2006
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    Take it to a kiln and bake it. Then refinish.

  5. #5
    There are only a few types of beetles (which aren't very common) that can actually infest dry wood. What you're seeing are probably larvae that got into the wood when it was wet. They've matured into beetles and the holes you see are them exiting the wood.

    If it's dried out by now the odds are that it will be inhospitable to future infestations and that the larvae will either leave or die off by themselves. Just takes time.

  6. #6
    Join Date
    Oct 2007
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    Heat sterilization is the only approved method to kill any bugs in the wood. The core of the lumber needs to be heated to 133f or greater.

    FWW magazine had an article a few years back about an easy and inexpensive home built sterilization chamber that you can make in order to sterilize your lumber. If you send me a pm with your email address I'll forward a copy of the article to you.

  7. #7
    Powderpost beetles can live in the wood for several YEARS before they bore out, so get the slabs heated like Scott says. Better safe than sorry.

  8. #8
    Join Date
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    Having been the victim, I agree with what the others say. Heat and refinish.
    "the mechanic that would perfect his work must first sharpen his tools.” Confucius

  9. #9
    I would verify the temp needed to kill bugs. Perhaps a Minivan in the sun on a hot day might achieve that temp. I baked a piece of white oak in my oven that was the top for a jewelry chest and haven't had a problem so far.........1 year ago.

  10. #10
    Join Date
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    I used a hatchback in the hot sun once. We had a series of very hot days, it was in direct sun, and the boards were directly under the window.

    My advice is to stop what you are doing, get it out of your house, and don't bring it back inside until you have done something to be sure the bugs are dead. The peace of mind is worth it. You don't want to spend the next twenty years wondering if they have now infested the framing of your house.

  11. #11
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    I suppose theoretically you could bag it up and fill the bag with any gas other then oxygen such as CO2 or N2. I have no idea how long this would take and I am sure even longer for the eggs. A vacuum would do the same. Freezing I doubt it.
    Maybe you could put it inside a house being tented for termites.
    Bill D.

    http://www.powderpostbeetles.com/col...le-larvae.html

  12. #12
    Join Date
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    First thing to do is get rid of the bark. wood boring beetles lay their eggs in the bark. When hatched they enter the wood and start doing damage. At maturity, they bore out (hence the holes) and start the cycle all over again. The beetles you have are likely Lyctids. They generally infest hardwoods. You can remove the bark with a relatively dull draw knife (I work with live edge all the time and that is my go to tool). Keeping the bark on is a BAD idea.
    Bracken's Pond Woodworks[SIGPIC][/SIGPIC]

  13. #13
    Thank you for all the advice, it seems like the best way to move forward is to bake it and refinish it. I will try to get more pictures up tonight, I'm not sure why that wasn't working.

  14. #14
    Quote Originally Posted by David Helm View Post
    First thing to do is get rid of the bark. wood boring beetles lay their eggs in the bark. When hatched they enter the wood and start doing damage. At maturity, they bore out (hence the holes) and start the cycle all over again. The beetles you have are likely Lyctids. They generally infest hardwoods. You can remove the bark with a relatively dull draw knife (I work with live edge all the time and that is my go to tool). Keeping the bark on is a BAD idea.
    This is something I would like to avoid considering all the work i put into keeping it on. I actually used glue, epoxy, and poly, in various stages of this project, where the bark contained cracks and crevices or was detaching from the wood. If I could bake it properly, won't that take care of anything left inside?

  15. #15
    Bugs that got into the wood when it was green probably don't present a danger to the dry wood in your house. Generally speaking, bugs that eat hardwood don't eat softwood and vice versa. Likewise with bugs that attack wet wood vs dry wood. In fact, I don't think I personally have ever seen powderpost type beetles infest wood that was truly dry. I'm not saying they don't exist, but they aren't likely to come in with a piece of wet wood.

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