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Thread: Air dried wood seems too dry

  1. #1

    Air dried wood seems too dry

    I milled some 4/4 pecan about a year ago here on the Texas coast, and its been stickered in my backyard since. I just ran it through a planer down to 3/4 and I was curious about MC. I have a pin meter and I measured the surface at around 9% and thought that couldn't be right so I cut into a piece so I could measure the center of the wood, and it still reads about 9%. I thought maybe I wasn't getting good penetration since pecan is so hard, so I drilled some small holes for the pins and its still at 9%. I'm starting to suspect the meter at this point (https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1), it has multiple modes, and pecan is definitely a hardwood (I assume, considering how hard it is) and of course it get a different reading in the softwood mode, but that can't be right. I know its been hot lately, but it hasn't been dry outside. I didn't think it was possible to air dry down to 9% and I've read that equilibrium in my area is around 15%. Should I try another meter, or is there something else I don't know about pecan, or any advice?

  2. #2
    I agree something doesn't sound right.

    Where I am at we average around 60% humidty & acclimated air dry runs 12-14%

  3. #3
    It's possible but unlikely given the environment you describe that the wood is that dry. For a definitive test of the meter's accuracy do an oven dry test of a pecan sample. For a less precise test, check some wood that has acclimated in your shop and compare that to the expected emc given recent humidity.

  4. #4
    Join Date
    Feb 2008
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    E TN, near Knoxville
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    Measure it a better way

    You can use the oven dry to check the absolute moisture content of any small sample of wood. No moisture meter needed. Extremely precise.

    I wrote about the oven dry method here:
    https://sawmillcreek.org/showthread....ven-dry-method

    (To avoid confusion read only the first two messages. After that someone sidetracked the thread by asking about using a microwave to dry wood turnings which has nothing to do with the oven-dry moisture test.)

    This partial chart shows the average measured EMC for points in Texas

    EMC_Texas.jpg

    The USDA publication "Air Drying Wood" has more charts and more information.
    It has complete charts, the oven dry method, and all about air drying.
    https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf

    JKJ

  5. #5
    Quote Originally Posted by John K Jordan View Post
    You can use the oven dry to check the absolute moisture content of any small sample of wood. No moisture meter needed. Extremely precise.

    I wrote about the oven dry method here:
    https://sawmillcreek.org/showthread....ven-dry-method

    (To avoid confusion read only the first two messages. After that someone sidetracked the thread by asking about using a microwave to dry wood turnings which has nothing to do with the oven-dry moisture test.)

    This partial chart shows the average measured EMC for points in Texas

    EMC_Texas.jpg

    The USDA publication "Air Drying Wood" has more charts and more information.
    It has complete charts, the oven dry method, and all about air drying.
    https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf

    JKJ
    John,

    When getting your sample to test, how far from the end of the board would you get your sample? I would hate to cut a perfectly good 6' board in half.

  6. #6
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    Quote Originally Posted by Matthew Curtis View Post
    John,

    When getting your sample to test, how far from the end of the board would you get your sample? I would hate to cut a perfectly good 6' board in half.
    Unfortunately, the documents recommend taking a sample from the middle of a board. Only a small sample is needed assuming a scale accurate for low weights.

    However, since your boards are probably well acclimated to the environment and your existing meter reads consistently across the board you might be safe in cutting a small sample out of the edge of one board, trying to stay at least a little away from the end grain. For the ebony I used small samples, no larger than 1"x1.5"x1/2".

    This assumes the meter is not stuck on 9%! Checking a few other pieces of wood could prove it is getting different readings even if calibration is an issue. It would be nice to find someone close with a meter to check yours against. Road trip! Drive down to TN and we can check it against my Wagner pinless meter!

    Another thing you might do - if you have a plan for a project for some of the boards that includes shorter pieces maybe you could make a cut through one that wouldn't ruin it's usefulness.

    Also, if the boards are 4/4 and you brought into an air conditioned shop to plane, perhaps they have reached 9%. ??

    JKJ

  7. #7
    I know a few locals with meters I could compare with. I don't have a scale, and at this point I'd almost rather just buy another meter than buy a scale, assuming that's even the problem, of course I know some people with kitchen scales that will probably do the trick.

    About how long does the oven test take, I've seen some people say up to 24 hrs., and how often do you check it.

  8. #8
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    Quote Originally Posted by Nathan Jordan View Post
    ...I don't have a scale, and at this point I'd almost rather just buy another meter than buy a scale, assuming that's even the problem, of course I know some people with kitchen scales that will probably do the trick.

    About how long does the oven test take, I've seen some people say up to 24 hrs., and how often do you check it.
    Scales can be inexpensive and handy to have. This one is up from the $8 I paid but still won’t break the bank.
    https://smile.amazon.com/American-We.../dp/B002SC3LLS

    I have 4 kitchen scales. None of them have the precision needed to work with small samples although I do use them for checking the progress of air drying turning blanks. I have several precision scales and a laboratory triple beam balance. The tiny one in the Amazon link is perfect for this task.

    The time depends on the type of wood and the starting moisture content. Hard, dense, very fine grained wet wood with closed pores will take longer. As I wrote in the message linked to I checked the weight every few hours. Don’t forget to record the initial weight.

    JKJ

  9. #9
    Join Date
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    Fairbanks AK
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    You could spit in your hand, set the pins on your MM in the puddle. Should read 35% plus.

  10. #10
    Join Date
    Oct 2007
    Location
    New Hill, NC
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    I question the accuracy of your meter. On the Texas coast EMC will be in the 15% neighborhood.

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