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Startling results from moisture-meter - viewer discretion advised

Post in 'The Wood Shed' started by mikeathens, Dec 23, 2008.

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  1. mikeathens

    mikeathens New Member

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    I posted some time ago about poor secondary combustion in my Mansfield. So, I ordered a moisture meter. I stuck it in my hand (read 36%). I stuck it in some door trim (2%). I stuck it in some planed, dry walnut that for making picture frames (2%). I stuck it in one of my log cabin's logs (0%). I go out and get some firewood and split the splits. Red oak that has been in the woodshed for 2 years (28%). Black locust drying for two years (35%). Both seem unreal numbers.

    Then, I got a 10" long piece of 1"x6" oak that was left over from when I sided my barn FOUR YEARS AGO. Again, 1"x6"x10". I use this stuff for kindling. I split it into about 5 pieces, and test the interior of the wood: 28% Zuh?

    Does anyone know if temperature affects these things (it's a cheap Chinese made meter with four prongs, digital readout). The instruction are written in broken English (actually pretty funny to read), but doesn't give any info on the "correct temperature". Should I assume "STP" (standard temp and pressure, for you non-engineer/scientific/chemistry types)? I have no "benchmark" known moisture content wood to go off of. This thing says it's accurate between 2% to (I think) 40%, with +/- 1% accuracy.

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  2. LLigetfa

    LLigetfa Minister of Fire

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    Sounds like a good reason not to get one. I'll just keep SWAG'ing.

    Part of the inconsistency may be that some readings are on an old surface while others are freshly exposed. I don't know if there is any truth to it but I heard the four prong ones are difficult to get equal penetration of all the prongs on uneven surfaces.
  3. free75degrees

    free75degrees New Member

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    You could check the weight of one of those pieces of oak before and after putting it in an overn at 200 degrees for several hours. Then stick it in the oven for some more time then weigh again and repeat until the weight stops changing, then take the total weight change and divide by the original weight then compare that to the meter reading.
  4. gzecc

    gzecc Minister of Fire

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    Sounds like yours is reading high. If you touch your fingers (normally moisturized) it should be approx 30%. If you wet your fingers you will see the numer rise. Be sure to plunge the barbs 5mm into the wood. This is sometimes difficult. Your #s look to be 20% too high. Change the battery and try again.
  5. Pagey

    Pagey Minister of Fire

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    I don't think I could safely get the barbs on my 2 pronged meter 5mm into the oak I have. How many times can you bury it that far and the meter still hold up, I wonder?
  6. Slow1

    Slow1 Minister of Fire

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    And don't forget - to get an accurate reading in your hand you want to plunge those barbs 5mm into them too! It's all in the name of accurate science and getting a fair apples to apples measurement after all isn't it? :)
  7. gzecc

    gzecc Minister of Fire

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    I agree, however thats how my meter says it should be used to be accurate.
  8. mikeathens

    mikeathens New Member

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    Well, I definitely am not going to get them 5 mm into oak, either. I pushed and pushed and finally realized if I was going to get them in that far, I would probably be looking at a new meter each time I wanted to do a test. No thanks at $27/test. guess I should have ordered a whole case of them...

    Seriously, I wonder how much accuracy i'm losing...pine is about the only thing I can see burying those things to the hilt in.
  9. gzecc

    gzecc Minister of Fire

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    The meters are good to get a relative state of your supply. I assume mine is in 10% of accuracy. I only chech newly split (same day) splits. I only burn when it shows <21%
  10. Pagey

    Pagey Minister of Fire

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    Tested my finger last night out of curiosity...30%. I did not go the full 5mm, either! :)
  11. LLigetfa

    LLigetfa Minister of Fire

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    ...and here we were taught in school that the human body is 98% water. I wonder what else they lied about?
  12. Adios Pantalones

    Adios Pantalones Minister of Fire

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    Males are about 60% water, females are about 55% water. The meter doesn't read that high, so you need to remove a sample of your body, weigh it, then put it in a 200 degree oven until it stops losing weight :)
  13. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Chuck a small bit the size of the prongs into your cordless drill and poke holes in the split about an inch or less or so.
  14. mikeathens

    mikeathens New Member

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    You soooooo smart BB. How fast did you figure that out? That type of enlightenment usually only comes to me after a 12-pack.
  15. jadm

    jadm New Member

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    Does using one of these on oneself at 5mm depth require a tetnus shot afterwards. 8-/

    I hate shots.

    Externally I get a reading of about 19% - we live in a dry climate and I am past my prime.

    I use a small nail and a hammer to get a 5mm depth on the wood I check. (Does it require a tetnus shot I wonder.) :roll:

    The moisture meter is a fun toy for me when I feel particularly compulsive about my wood.

    The real test for me is simply taking 2 splits and hitting them together and checking out the sound they make. Only tools needed are 2 hands and 2 ears. No shots required. :coolsmile: I learned it here.
  16. JerseyWreckDiver

    JerseyWreckDiver New Member

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    Most moisture meters, especially those with instructions not written in a Chinese version of broken English, come with a chart of compensation factors for different wood species. Meaning two species of wood at exactly the same moisture content can give you different readings. I'll see if I can find my chart and post it.

    Several years ago I adopted a methodology which has been serving me well. I don't buy anything, let me repeat that, ANYTHING made in China. Consequently I don't shop, ever, in Chinamart or Garbage Depot.
  17. gzecc

    gzecc Minister of Fire

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    People with oposable thumbs shouldn't need to poke holes in their fingers.
  18. lexybird

    lexybird Minister of Fire

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    find a few chunks of good dry average hard wood check it several times and you get a good reasonable reading on your meter ,now burn them and mark them see if it is ideal to burn and what you think and expect a good dry split produces for btu ,and use that number as a gauge to whats dry ,dont be so concerned with how accurate the given number is to everything else oak moldings ,barn siding and your butt cheeks ..as long as its accurate to itself if that makes any sense and is repeatable
  19. JerseyWreckDiver

    JerseyWreckDiver New Member

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    So far as what's considered dry according to the moisture meter 14-16% is dry, everything has some moisture in it. 16-20% is just considered damp and wet starts from 22% and up. For firewood 18-20% would be ideal but few things in life are ever ideal, then plug in those adjustment factors for a good hard wood like Locust and 25% may be ideal. Typically 25% is totally acceptable. Higher than that, well, your just cooking off a little water till you get to full bore.

    Also, for testing deeper in the wood, drive a couple small finish nails in and contact them with the probes... its archaic but it works.
  20. Ducati996

    Ducati996 Member

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    You guys test all wrong - use your BUM as the real test. Have your friend, wife or doctor just stick the probes into your BUM. Right then and there you should know where you stand on moisture. :)
  21. Malatesta

    Malatesta New Member

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    I am not going downtown into the city and find some bum to stick the meter in , no way !
  22. Malatesta

    Malatesta New Member

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    Ducati were do you find these bum's that volunteer.
  23. karri0n

    karri0n New Member

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    You probably used more than one finger for the test. this threw the measurement waaaay off because the current had to travel all the way down the fingers , through the hand, and back to the other probe, rather than traveling the 1/2" that it should have. Jam that thing into your eye(or any other attached tissue) and you will get a more accurate reading.



    edit: anyone try testing the moisture of a glass of water?
  24. PunKid8888

    PunKid8888 New Member

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    or how about a peice of wood (cooled) that did not burn completely in the stove
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