Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: Moisture content: How much is too much?

  1. #1
    Join Date
    Dec 2009
    Location
    Madison, WI
    Posts
    206

    Moisture content: How much is too much?

    To introduce myself, I'm a college student learning to make things out of wood. I have a few years' experience working with jewelry, and spend enough time mucking about with acoustics and speaker design that I'm trying to learn how to work with it as well.

    After looking for a fancy wood for a headphone project, I found a likely candidate: Regnas, otherwise known as borneo rosewood. Aside from a tendency to cause rashes and irritation when green, borneo rosewood seems to be a great wood - it's cheap, and when given a bit of wax or laquer takes on a color from bright red deep red color with black stripes.

    http://www.amazonexotichardwoods.com...y_Code=TB-BORO
    The problem with this wood is that it's usually sold as turning stock, which I'm told can have too much moisture to be cut into thin slices or CNC milled without splitting or warping. How much moisture should I be looking for?
    Last edited by Joseph Shaul; 12-03-2009 at 02:43 AM.

  2. #2
    Join Date
    Oct 2006
    Location
    somewhere east of Queen Creek, AZ - South East of Phoenix
    Posts
    8,529
    Welcome to the family.
    In terms of moister content. Less is better. Differant species react differantly so its hard to give you a difinitive answer.
    Do you have a moisture meter ?
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  3. #3
    Join Date
    Dec 2009
    Location
    Madison, WI
    Posts
    206
    Quote Originally Posted by Don Baer View Post
    Welcome to the family.
    In terms of moister content. Less is better. Differant species react differantly so its hard to give you a difinitive answer.
    Do you have a moisture meter ?
    Not at the moment, no. Strictly speaking, I haven't really got any tools at all.

  4. #4
    Join Date
    Oct 2006
    Location
    Tokyo Japan
    Posts
    15,807
    Welcome to the Family!

    You really need a moisture meter to find out if it is dry or not, I guess you could weigh it and then see what it is supposed to weigh and compare the two weights

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  5. #5
    Join Date
    Jul 2009
    Location
    Amherst, New Hampshire
    Posts
    10,604
    Welcome !
    Faith, Hope & Charity

  6. #6
    Join Date
    Oct 2006
    Location
    ABQ NM
    Posts
    30,020
    Joseph, as Don mentioned, it can vary from species to species. That said, I think a lot of woodworkers consider about 12% moisture or less to be "dry". Keep in mind that wood will reach an "equilibrium" moisture content that varies depending on the relative humidity of the air around it. In a humid environment, 15% might be as dry as the wood will ever get. In the desert where Don lives, it might get as low as 4% or 5%.

    Quote Originally Posted by Stuart Ablett View Post
    ...You really need a moisture meter to find out if it is dry or not, I guess you could weigh it and then see what it is supposed to weigh and compare the two weights

    Cheers!
    Actually, you can very accurately determine the moisture content with a good scale and an oven. (That's how a good moisture meter is calibrated.) The downside is that you have to cut samples from the block of wood and dry them, and they'd be best from the middle of the blank. Unfortunately, if you try to dry the whole block in the oven, there's a good chance it'll crack.

    For those who are curious, here's how to tell moisture content with a scale and an oven. (Leftover knowledge from my days working in a materials testing lab.) While it might not be practical for checking a single turning blank, with just a few representative samples, you can get a good general idea of how wet a whole stack of lumber is by using this method.

    1. Weigh the wet wood.
    2. Dry the wood thoroughly in an oven. It's dry when it's no longer losing weight.
    3. Weigh the dry wood shortly after removing it from the oven. (Otherwise, it can absorb new moisture from the atmosphere.)
    4. Subtract the weight of the dry wood from the weight of the wet wood. The result is the weight of the water.
    5. Calculate the percentage of moisture with this formula:

    (Weight of the water / weight of the dry wood) x 100 = % moisture
    Example:

    Wet wood = 500 grams
    Dry wood = 400 grams
    Water weight = 100 grams

    100 / 400 = 0.25
    0.25 x 100 = 25% moisture content
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  7. #7
    Join Date
    Dec 2007
    Location
    Tellico Plains, Tennessee
    Posts
    4,353
    Vaughn
    When you speak of an oven... are you talking about a conventional oven on low heat or a microwave - or both.. I sometimes dry wood in a microwave if it's really obviously wet... I don't have a scale or a moisture meter so I tend to use a "feels about right" method of determining if it's dry... so far I've been relatively successful with the woods I'm working with.
    Chuck
    Tellico Plains, TN
    https://www.etsy.com/shop/TellicoTurnings
    My parents taught me to respect my elders, but it's getting harder and harder to find any.
    If you go looking for trouble, it will usually find you.

  8. #8
    Join Date
    Feb 2007
    Location
    Westphalia, Michigan
    Posts
    955
    Don't forget the sometimes important fact that some woods need the end grain sealed before drying. Most woods have capillaries (small tubes) that will carry water out of the end grain much faster than out of the face of the board. This uneven drying will cause stresses to build up near the end of the board and then cracking. By sealing the end grain with wax or even a good paint, you force the wood to dry mostly out of face grain generally causing less stress. I would saw a block like that first and after sealing the end grain attempt to dry it. Good luck.

  9. #9
    Join Date
    Oct 2009
    Location
    Bradford, Vermont
    Posts
    425
    Quote Originally Posted by Vaughn McMillan View Post
    Joseph, as Don mentioned, it can vary from species to species. That said, I think a lot of woodworkers consider about 12% moisture or less to be "dry". Keep in mind that wood will reach an "equilibrium" moisture content that varies depending on the relative humidity of the air around it. In a humid environment, 15% might be as dry as the wood will ever get. In the desert where Don lives, it might get as low as 4% or 5%.



    Actually, you can very accurately determine the moisture content with a good scale and an oven. (That's how a good moisture meter is calibrated.) The downside is that you have to cut samples from the block of wood and dry them, and they'd be best from the middle of the blank. Unfortunately, if you try to dry the whole block in the oven, there's a good chance it'll crack.

    For those who are curious, here's how to tell moisture content with a scale and an oven. (Leftover knowledge from my days working in a materials testing lab.) While it might not be practical for checking a single turning blank, with just a few representative samples, you can get a good general idea of how wet a whole stack of lumber is by using this method.

    1. Weigh the wet wood.
    2. Dry the wood thoroughly in an oven. It's dry when it's no longer losing weight.
    3. Weigh the dry wood shortly after removing it from the oven. (Otherwise, it can absorb new moisture from the atmosphere.)
    4. Subtract the weight of the dry wood from the weight of the wet wood. The result is the weight of the water.
    5. Calculate the percentage of moisture with this formula:

    (Weight of the water / weight of the dry wood) x 100 = % moisture
    Example:

    Wet wood = 500 grams
    Dry wood = 400 grams
    Water weight = 100 grams

    100 / 400 = 0.25
    0.25 x 100 = 25% moisture content
    Very well explained, Vaughn.

    Chuck - a conventional oven is preferred because a microwave is too fast; it's easy (DAMHIKT) to scorch wood in a microwave, even if it's run on a 1:10 duty cycle. A conventional oven set to 150-200 (fahrenheit) works well, and best at about 150 (the minimum lowest setting for most conventional ovens). There's no need to bring the temperature all the way up to the boiling point, risking scorching - 150 will drive the moisture out very effectively & quickly.
    -- Tim --

  10. #10
    Join Date
    Dec 2006
    Location
    RETIRED(!) in Austintown, Ohio
    Posts
    5,323
    Quote Originally Posted by Vaughn McMillan View Post
    ...Actually, you can very accurately determine the moisture content with a good scale and an oven. (That's how a good moisture meter is calibrated.) The downside is that you have to cut samples from the block of wood and dry them, and they'd be best from the middle of the blank. Unfortunately, if you try to dry the whole block in the oven, there's a good chance it'll crack.

    For those who are curious, here's how to tell moisture content with a scale and an oven. (Leftover knowledge from my days working in a materials testing lab.) While it might not be practical for checking a single turning blank, with just a few representative samples, you can get a good general idea of how wet a whole stack of lumber is by using this method.

    1. Weigh the wet wood.
    2. Dry the wood thoroughly in an oven. It's dry when it's no longer losing weight.
    3. Weigh the dry wood shortly after removing it from the oven. (Otherwise, it can absorb new moisture from the atmosphere.)
    4. Subtract the weight of the dry wood from the weight of the wet wood. The result is the weight of the water.
    5. Calculate the percentage of moisture with this formula:

    (Weight of the water / weight of the dry wood) x 100 = % moisture
    Example:

    Wet wood = 500 grams
    Dry wood = 400 grams
    Water weight = 100 grams

    100 / 400 = 0.25
    0.25 x 100 = 25% moisture content
    Maybe...

    The formula will only work if you consider the 'dry' wood to have achieved 0% moisture - which is a virtual impossibility.

    You will have removed 20% of the initial weight of the wood, and most of it will have been moisture. A few grams of other substances will also have been removed, but so little as to be of no consequence.

    The actual moisture content, though will have been something greater than the 25% in the example, because of the amount that's still in there.

    Once dried in this manner, it's still not at it's 'natural' moisture content. That will be achieved when the wood reaches an equilibrium within its final environment. As previously mentioned, that level could be anywhere from a couple percent up to maybe fifteen percent or more.

    Don's Arizona summer level might be only a couple percent, but Royal's Hawaiian tropical climate may result in something more like fifteen percent.

    For most furniture, an average moisture level in the 8~10% range will be quite normal and acceptable. The climatic extremes cited above will result in much more wood movement - and will also require planning for it during the construction.
    Jim D.
    Adapt, Improvise, Overcome!

Similar Threads

  1. Moisture content
    By Bob Blunden in forum General Woodturning Q&A
    Replies: 5
    Last Post: 11-02-2013, 01:48 PM
  2. A very good article just posted about why wood moisture content matters
    By Dom DiCara in forum General Woodworking Q&A
    Replies: 1
    Last Post: 03-06-2012, 06:12 AM
  3. Fine Woodworking DVD vs Online Content
    By Bill Satko in forum General Woodworking Q&A
    Replies: 2
    Last Post: 07-09-2010, 03:40 PM
  4. It is all about content
    By Ken Garlock in forum Off Topic Discussion
    Replies: 16
    Last Post: 11-13-2007, 01:21 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •