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Thread: Drying Green Blanks?

  1. #16
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    desiccant

    Quote Originally Posted by Roger M. Davis View Post
    Take a look at this on YouTube:https://m.youtube.com/watch?v=DaaTbDTUsg0 Some types of cat litter contain silica gel which is a desiccat (a hygroscopic substance used as a drying agent). They can even have color that turns when full. Then just bake in oven at low temp. till dry. That's the packets found in Rx bottles etc.
    Have not tried it yet but sounds great. Roger

    You can get indicator desiccant at Amazon. https://www.amazon.com/gp/product/B000OUXA2Q/
    I bought several of these, at first to recharge some air line dryers without paying for the expensive disposable cartridges. Now I also use them to keep CA glue from setting up. Since moisture can activate the glue and moisture can go through most of the plastic bottles, I keep the glue in a sealed container with some desiccant.

    Since I took this picture I found a much better/larger container in the housewares section at Walmart. It has a rubber seal and latch so I don't have to unscrew a lid each time.

    CA_glue_storage_IMG_5481.jpg

    The desiccant beads turn change color from blue to pink as they pick up moisture. I recharge them by pouring into a tray and heating in a toaster oven I keep in the shop.

    One problem I can imagine is it might take a LOT of desiccant to pull all the water out of a bowl. Desiccant beads alone might dry the wood too fast, but the cat litter mixture might be perfect. To recharge in the oven takes a long time.

    JKJ

  2. #17
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    This has always been my choice of drying for green wood blanks and I have rarely had any checking or splitting.
    1. I rough turn green blanks to 1/10th of diameter.
    2. Immerse blank in Denatured alcohol for 24-48 hours depending on size.
    3. Remove and let surface day for 1-2 hours.
    4. Wrap in brown paper and tape up tight like a mummy and weigh.
    5. Weigh piece weekly until weight loss starts to slow .
    6. Weigh daily until I reach same weight 3 days in a row.
    7. Finish turn and apply Finish treatment of choice.
    Regards, Ken

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  3. #18
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    [QUOTE=Ken Glass;2873052]This has always been my choice of drying for green wood blanks and I have rarely had any checking or splitting.
    1. I rough turn green blanks to 1/10th of diameter.
    2. Immerse blank in Denatured alcohol for 24-48 hours depending on size.
    ...

    Something that might speed the drying even more, between your steps "1" and "2". The other John Jordan put compressed air inside a freshly hollowed form and an amazing amount of free water bubbled out of the pores. Removing a lot of the free water that way would let give the bound water a path for more hasty escape.

    Doing this with the hollow form only needed one hand to make a seal against the opening but for a bowl I think a flat piece of mdf or something with a small hole for the air nozzle, perhaps with a layer of foam to seal against the rim would work. This method might not work as well for a thick roughed wall for some species though, would be interesting to try.

    JKJ

  4. #19
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    John,
    I have been known to blow compressed air in and around the blank/HF to remove surface moisture before wrapping the blank as well. Once wrapped up I let the DNA do the moisture extraction.
    Regards, Ken

    Become a Contributor at SMC and keep this great source of Knowledge and help from becoming only a memory.

  5. #20
    From my experience... Boiling rough turned bowl can help prevent some cracking, but it might not prevent much of the warping. If you have a wood that warps a lot then consider turning the bowl more twice. If the wood is freshly cut then make your first rough turning thicker than 10% to be on the safe side. Then rough turn again (one or more times) as it starts to dry/warp, but remember to keep bowl sealed between turnings (i.e. Anchor Seal, How Wax, School Glue, Bag, Box, etc..) to lessen cracking. Eventually you'll figure out which woods are Ok to twice turn (cherry & walnut) and which ones might need to be turned more than twice (freshly cut oak or persimmon). Bonus: You'll experience less bouncing and better control the more times the bowl gets turned.

    Personally, I don't always have time to rough turn my green wood the day it's cut. I've gotten decent results coating my green blanks in hot wax (using a large electric skillet) which then gives the wood a chance to harden off and warp a little before I get to the initial rough turning.

  6. #21
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    preventing oval warping with constraint?

    Quote Originally Posted by Karl Loeblein View Post
    From my experience... Boiling rough turned bowl can help prevent some cracking, but it might not prevent much of the warping. ...
    I've wondered about the possibility of minimizing warp or "unwarping" a warped bowl with steam or boiling. Many types of wood are pliable enough to allow bending them after steaming, and green boards off the sawmill can be constrained from warping by stickering and drying under weight, could a freshly rough turned bowl be dried while the rim is prevented from freely moving?

    For example, if the rim were jammed in a sturdy hole it just barely fit into and then dried slowly as normal it seems to me it might take the "set" and stay round enough to finish turn even if the walls were thinner. While I originally imagined stout metal ring, other methods might make more sense, at least for a test.

    One idea is to cut a circle out of a piece of plywood that just fit around the rim. The plywood would need to be big enough to be strong, but based on my experience drying stickered lumber I'm not convinced the force would be extremely high.

    Who knows, maybe constraining the movement might cause other problems such as encouraging cracks, but can't know until tried. Has anyone tried this? If not, a test wouldn't be difficult for someone who turned a lot of green bowls. Just turn two close to identical from the same log, omit the boiling, then constrain one and not the other, and dry as usual. If that proved to have problems, repeat the test with three more roughed bowls, one boiled and constrained, one boiled and not constrained, and the third not boiled as a control.

    Anyone want to try this? You could be rich and famous. it works, you can put my name with yours on the patent! (Ha! Just kidding, I have enough patents. But even if it does, I'd be surprised if someone else hadn't thought of this and wrote about it it decades ago.)

    If constraint did work, I can envision a jig that had adjustable jaws that could be snugged up against the rim, say six or eight, and bolted down. The jaws could be snugged periodically as the rim shrunk while drying. A more robust version could have a screw jack on each jaw.

    JKJ

  7. #22
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    I use hose clamps. There isn't much spring, so they need to be tightened periodically.

  8. #23
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    Quote Originally Posted by Glenn C Roberts View Post
    I use hose clamps. There isn't much spring, so they need to be tightened periodically.
    That sounds too easy!

    Do they prevent bowl from going out of round?

  9. #24
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    Midland, MI
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    Quote Originally Posted by John K Jordan View Post
    I've wondered about the possibility of minimizing warp or "unwarping" a warped bowl with steam or boiling. ...could a freshly rough turned bowl be dried while the rim is prevented from freely moving?

    For example, if the rim were jammed in a sturdy hole it just barely fit into and then dried slowly as normal it seems to me it might take the "set" and stay round enough to finish turn even if the walls were thinner.... One idea is to cut a circle out of a piece of plywood that just fit around the rim.
    JKJ
    Interesting idea. But the walls are going to shrink inward, so you'd need something inside the bowl pressing out to keep the bowl from going oval.

    So instead of a hole, cut a plywood disk sized to jam tight inside the rim. You'd have to cut some holes in it for circulation so the bowl could dry. Or maybe, instead of a disk, you could just wedge a small board inside touching opposite sides of the rim at the point where it wants to shrink the most. That would be 90 degrees from where the pith falls on the rim.
    Last edited by Dave Bunge; 12-07-2018 at 1:49 PM.

  10. #25
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    I wonder if constraining from the inside could cause cracking on the outside as the wood shrinks.

    I'm imagining that even if a bowl constrained on the outside did go a little oval when shrinking, perhaps the warping might not be as crippling as it would be otherwise. I like your idea of using wedges but perhaps on the outside, driving them in a little further as needed.

    Quote Originally Posted by Dave Bunge View Post
    Interesting idea. But the walls are going to shrink inward, so you'd need something inside the bowl pressing out to keep the bowl from going oval.
    So instead of a hole, cut a plywood disk sized to jam tight inside the rim. You'd have to cut some holes in it for circulation so the bowl could dry. Or maybe, instead of a disk, you could just wedge a small board inside touching opposite sides of the rim at the point where it wants to shrink the most. That would be 90% from where the pith falls on the rim.

  11. #26
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    Hopefully you can see the "defects" (?) on the base of this 10" unfinished butternut dog dish. I used a hose clamp on the base to stop the crack progression and warping in that area. It worked perfectly. I also clamp the base of end grain bud vases and that also works. Clamps on the rims of bowls I have not tried because I like the warping, but it's easy enough to do.
    Attached Images Attached Images

  12. #27
    Quote Originally Posted by John K Jordan View Post
    I've wondered about the possibility of minimizing warp or "unwarping" a warped bowl with steam or boiling. Many types of wood are pliable enough to allow bending them after steaming, and green boards off the sawmill can be constrained from warping by stickering and drying under weight, could a freshly rough turned bowl be dried while the rim is prevented from freely moving?
    ...
    Would keeping boards from warping by 'stickering and drying under weight' bind up some stress in the wood? Just thinking these internal stresses could be reactivated by cutting the wood or a change in humidity. In other words, is it better to leave bowl unconstrained so no stresses are introduced, or constrained in order lessen any warping? Agree, this would make an interesting experiment if someone had time.

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