After years of putting it off I finally called WM and got the Wagner MMC220. The first lumber I checked was some ash I milled a year ago and recently took to the Kiln. I remember picking up the wood and the operator showed me their meter which read the wood being at 7.5%. It has been in my shop (no central air system) since last June stacked on my lumber shack. I checked it today which showed it to be 11%. I am planning on using this wood for a dining table. Is this a normal increase in percentage for lumber taken out of a kiln and placed into a workshop with no climate control? I checked most of my other kiln dried woods in the shop and got about the same readings. I also checked some furniture in my house and got readings of around 8.5 to 10% MC. I am thinking I might need to take my stock inside my house and acclimate to a lower MC content before I build the table. I also read where some furniture builders will shrink wrap their stock once it gets to 8% to prevent any change before the piece in placed into a home. Any advice would be appreciated.
Personally, I think you will be just fine. Leaving the wood where some humidity can get to it is normal and so is the increase since it left the kiln. I think that you are close enough at 11% that you will not notice any difficulty when the project is put in your home. I am in a similar situation recently making a barrister's bookcase and it is doing just fine in our house.
As the other two replies have said, you should not need to be concerned about 11% moisture in wood for furniture. However, you should always leave a means for the boards to expand or shrink across the width of the board (just because they will no matter what moisture content you start with).
The meter must be used for wood that has air underneath (that is, the meter is firmly placed in the lumber, but underneath the lumber there needs to be an air gap and not a metal table, another pieces of wood, etc.). The meter must be adjusted for the density of the species being tested.
In order for wood to go from 7% MC to 11% MC, the environmental conditions must have been in excess of 13% EMC or essentially over 70% RH. This high average humidity is rare, even outside. It would begin to increase the risk of rust on iron tools. Most of the USA has 12% EMC outside. In almost all situations, if the outside is 12% EMC, the inside would be drier. So, a shop would likely be 10% or 11% EMC, unless heated, in which case it would be even drier. Almost all homes in the USA have an average MC in the wood of 6% to 8% MC. Based on all this, I suspect that your meter is giving you the incorrect MC values. Perhaps you are using the incorrect density for the ash or the meter itself is out of calibration.
I suggest that you find someone with a pin meter that can check the MC of a piece of lumber and then you check the same piece in the same spot (with air gap nd no metal nearby, adjusted for density, etc.) and compare the two readings. If you can find a commercial kiln operation that uses an oven test, that would be even a better test.
In most of the USA, especially TN where you are, the inside furniture MC will be between 6% to 8% MC. Although you can air dry to 20% MC or even a little drier, in order to get wood that is very close to 7% MC, you will need to put the wood in a kiln, in a warm and dry room, in a warm attic, etc., so that it can dry down to this final value. The outside, even if you air dry for years, will only get to 12% MC, as that is the typical outside EMC in TN. Note that some people only air dry, but then when they bring the wood into a dry shop it does indeed dry to a lower MC value.
Ash is very prone to having insects...anobiid beetles and powerposts. So, it is prudent to have the final drying occur at 130 F or hotter for a day or so to kill any insects.
We know that wood shrinks as it dries...about 1% size change for a 4% MC change for ash. If you use 11% MC, it will eventually dry to 7% MC and with this 4% loss will be 1% shrinkage. For a leg, that might not be an issue, but for a table top, that shrinkage can be very troublesome. So, you might just go ahead and dry it to 7% MC and then you would not have to be concerned about potential shrinkage issues.
Quote from: GeneWengert-WoodDoc on December 15, 2014, 07:14:51 PM
In order for wood to go from 7% MC to 11% MC, the environmental conditions must have been in excess of 13% EMC or essentially over 70% RH. This high average humidity is rare, even outside. It would begin to increase the risk of rust on iron tools. Most of the USA has 12% EMC outside.
Saw the comments on RH and what is average for outside and got curious as I have lived so many different places over the years and have lived in sweltering humidity and deserts that seem dry.
Data was caveated with the following: Source from web site Current Results and research news & science facts
Average yearly relative humidity and daily number is the average of humidity readings taken every three hours throughout the day.
Texas
Average RH City
76 Brownsville
76 Corpus Christi
75 Houston
78 Port Arthur
75 Victoria
and Louisiana
74 Baton Rouge
78 Lake Charles
76 New Orleans
72 Shreveport
Washington
80 Olympia
84 Quillayute
73 Seattle
Wisconsin
73 Green Bay
72 La Crosse
73 Madison
72 Milwaukee
Arizona
53 Flagstaff
37 Phoenix
38 Tucson
46 Winslow
37 Yuma
Gene, A follow up to your reply and I really appreciate yours and everyone's help.
The unit I got is the wagner that Woodmizer sales. I used the appropriate setting for Ash according
to their instruction manual. I see where you suggest holding it away from the wood with air between the wood and the instrument. The instructions state to hold the meter directly on the face of the wood with three pounds of pressure. I held just slightly away from the board not directly on it and the meter showed the reading to be lower around 9percent. Learning as I go here. Also when I put the meter on the end grain and side grain directly on the wood is showed a lower reading (around 8percent) than when directly on the face grain which shows it to be 11percent.
Your thoughts?
Thanks for the help/advice.
I think Gene meant that the board needs to have air below it, not sitting on another board, or on a metal table etc. If it's the meter I think it is, then you do put it flat on the board.
Yes, flat on the board, but the board has to have air under it. I have a MMC210 from Wagner.
Quote from: WDH on December 15, 2014, 09:43:07 PM
Yes, flat on the board, but the board has to have air under it. I have a MMC210 from Wagner.
Thanks that helps,
I corrected my statement to explain it in more detail...sorry for the confusion.
Here is a link to the average EMC for many U.S. Locations by month.
www.esf.edu/scme/wus/documents/EMCofWoodFPL268.pdf
You will note that the EMC in TN in many locations runs about 13% which is not going to get the wood to 11%, partly because when approaching the EMC from the low side, you will end up not quite getting there... Maybe 1/2-3/4 %, so at 13% EMC, the surface will only get to around 12-1/4% MC, which is not high enough to get the core up to 11% MC. (This is called the hysteresis effect.)
Gene,
If you are willing to mention, which meter have you found to be the most accurate and is there a reasonably priced option? Your experience is much appreciated. My wife bought a Harbor Freight meter and as far as I can tell I would be as well off throwing darts at a dart board to guess moisture. I too need to buy a good meter. Not only that, the batteries cost more than the meter.
Quote from: GeneWengert-WoodDoc on December 15, 2014, 11:15:27 PM
Here is a link to the average EMC for many U.S. Locations by month.
www.esf.edu/scme/wus/documents/EMCofWoodFPL268.pdf
Thanks for the link. Found a calculator and a table on Wood Worker Source web site but this is a nice pamphlet as well.
The best moisture meter is one that costs around $200 and is made in the USA. I like both the pin and pinless meters. Both have some good features , but both have shortcomings. However, where one is not so good, the other covers that issue well, so together the two types are awesome. (Example: the pin meter is slow to use and is sensitive to wood temperature. The pinless is fast but is sensitive to wood density. The pinless measures the average quickly and the pin measures at one point so can measure gradients.) If you can afford only one meter, the Delmhorst model J2000 with the 26 ES electrode attachment will be the best for drying people. If you are in the East, their location in NJ is certainly good for speedy repairs when you drop the meter or run over it.
Note: The best meter is one that is used.
Note: When selling wood, always specify what the basis for moisture tests will be (include meter name and model) operated according to the manufacturer's instructions. I was recently at an operation that drove the pins into the core of the wood and used that value, while the kiln operation used the average MC determined by weighing and oven drying. You can appreciate why I was called in, as the two did not agree, so they wanted to know who was correct. Both were correct, but they were not measuring the same thing. In most cases, we are most concerned about the average MC and not the core, but if we were resawing, then the core is important.
The original posting asked about shrink wrapping. This is a great idea, but all you need is plastic wrap. You can buy a large size roll from Sam's and similar stores. The reason for wrapping, assuming your shop's humidity and the customer's humidity are the same, is that in shipping and storage between you and the customer can be at a different humidity. A wrapped product that is wrapped well will not let moisture in or out, so the MC will not change, even if the surrounding climate is cold, hot, too dry or too humid. The small cost for wrapping is indeed cheap insurance.
One other technique is to measure the MC just before shipping so you know and can document that the piece is correct. Without this info, you are just guessing. Some folks call this CYA...cover your &&&.
I sent my moisture meter to Wagner last week and they sent me an email today telling me they found no problems with the unit and that is was calibrated properly.
Before sending the unit I re checked my house furniture and got the following results.
White pine 10percent pie safe
Red oak 11 Percent, kitchen cabinets
both pieces I checked parts that did not have any finish.
When I got the meter I checked a kiln dried piece of white oak I had in my shop that read 12 percent. After being in my house for a week it read at 11.5.
I checked all my house furniture and never got a reading below 10 percent.
Wagner is sending my meter back so I will continue to check my lumber.
I do have a heat pump in my home if that matters much. I am guessing my wood is EMC of 10 to 12percent for my climate. I live in the mountains of Northeast TN.
123
Sounds like that would be a good conclusion and reasonable expectation.
I agree. Here in the South, we have a bit more internal humidity than those in the frigid, frozen, glaciated Northern Parts.
Quote from: WDH on December 22, 2014, 08:38:58 PM
frigid, frozen, glaciated Northern Parts.
What are you saying :snowball1:
He said that you have less moisture in your "Northern Part". ;D
Here is the EMC for July and August for
Madison, WI 13.4% and 14.4%
Shreveport, LA 13.8 and 13.6
Memphis, TN 13.03 and 13.1
Which meter would be best if used mainly for checking 2" slabs or 4" mantels? Also is there any plans on solar kiln class up at VT any time soon?
Sounds like a pinless...Wagner or Delmhorst...is what you need for this job.
VT holds a solar seminar every year about the same time.