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Thread: why does black locust wood crack

  1. #1
    Join Date
    Sep 2008
    Port Hope Ontario Canada

    why does black locust wood crack

    I have roughed out 2 bowls out of black locust and both have cracked the same
    the second one was soaked in dna for 3 days and cracked almost right away

    is this normal for this to happen to this type of wood

    and is there a way to save it
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  2. #2

    wood cracking

    your black locust is cracking because of moisture loss, i can quote Al Hockenbery.

    As wood grows it has 3 dimensions

    Verticle - the long grain
    Radial - across the growth rings center of the tree to bark
    Tangential - around the growth rings

    When wood dries it shrinks in the radial and the tangential directioons from 6 - 12 percent depending on the species. It doesn't shrink at all in the vertical. This is what post and beam construction with green logs relied on.

    Moist loss is most rapid through the endgrain.

    The pith is problematic because the wood wants to shrink radially which means from the center of the tree to the bark. This makes cracks in the pith open up.

    The wood also wants to shrink around the growth rings. This causes the long splits open up in a round log.

    Cutting through the pith releaves these stresses.
    you may try splitting the wood thru the pith and putting it in cardboard barrels with dry shavings for a year, this is not 100% not cracking and the wood will probably still warp
    Last edited by charlie knighton; 12-18-2008 at 10:56 PM.

  3. #3
    Join Date
    Feb 2006
    Northern Ohio
    I have had lots of Locust problems also, but it is a nice wood to work with. I seal all my locust blanks l00% , top, bottom, sides, inside, outside, I have had less problems since doing this. Anchorseal is the way to go. Locust just cracks alot. I do not know the science of it, maybe someone can help here.

  4. #4
    I've had oak crack in a similar way. I tend to think those kinds of cracks are best prevented by turning thin and then letting the bowl warp to it's final form. I haven't ever turned black locust, but some woods just don't cooperate regardless of how you try to control the drying process. If you have anymore of that wood try turning a bowl thin, like 1/4" walls, all in one turning, and let it warp to the shape the wood wants to be.

  5. #5
    Most of the time it cracks because it is drying too fast. This is why it is put into bags, sawdust piles, anchor seal, etc, to control the moisture loss. If you bring it into the house from a cool/cold shop, it will probably crack. Wood does not like sudden changes in temperature or humidity. I have noticed a tendency for trees that have been down for a year or so to crack more than others, and usually rather quickly. Not sure why. What I do now is to take the bowl, turn to final thickness, and soak in LDD (liquid dishwashing detergent which makes it easier to sand out), rinse it off, then wrap the outside in a couple of wraps of newspaper, then use some of the plastic film that you wrap boxes in to keep them from falling off a pallet, I wrap it around a couple of times, and stretch it out to put some pressure on the rim. I then cut out the paper in the inside of the bowl. This has proven to be very succesful with even the most difficult woods. I will dry it on the floor or a low table for a few days, then up on a wire rack. A 1/2 inch thick bowl dries in about 2 weeks, and a 1/4 inch thick bowl dries in about a week to 10 days. The main problem here is sanding it out. You need to power sand, and you need a lathe that will slow down to 20 rpm or so because any faster than that and you can't keep your hand or the sander on the wood. You can mount on the lathe and let the sander advance the wood, and let one hand serve as a brake/speed control. A little bit tireing for a long day as you have to hold the sander in one hand. As near as I can tell, there is no measurable difference in drying time, stability, or cracking with thin bowls if you soak in DNA, It does make the wood seem harder, and it is definatly harder to sand out.
    robo hippy

  6. #6
    Join Date
    Aug 2007
    Caledonia, Ohio USA.
    Blog Entries
    I'd say it dryed to fast. For some many different reasons.... most likely posted above.
    Have a Nice Day!

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