I am wondering if my new moisture metre is right or not becacuse I just tested it on some 4/4 pine that was sawn on August 16 ’02 (about 2 weeks ago) and it gave me an average reading of about 14%. How can this be? I know that the logs were chopped down over a year ago into 10′ sections, but would this have anything to do with it or is my new meter coo koo? It’s from Lee Valley, so I figured I couldn’t go wrong. Any thoughts would be appreciated.
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Replies
roamer:
Where were the logs stored b-4 they were sawn? Was it area of high humidity? Where has the sawn lumber been stored for the last 2 weeks? Area of high humidity?
Check your moisture meter on any kiln dry lumber you might have that happened to be stored in another area of stable humidity. It should be in range of 8% to 12%. It is not unusual to have air dry at 14%. What kind of meter? Pin or di-electric (no pins). What wood is your meter calibrated for and did you make the conversion from your conversion chart.
Finally, consider Bruce Hoadley's book, Understantding Wood from Taunton Press. It's worth every penny.
In my humble opinion.....
Have a good day.
sarge..jt
Where do you live? Do you think 14% is too high or too low?
There's a rough rule of thumb that sawn lumber air dries about one inch per year. In that case, your logs wouldn't dry very much in a year. and your sawn lumber hasn't had much time to dry. Are you thinking that 14% seems to be a pretty low value?
BJ
The first thing to realize is that moisture meters are not accurate above the Fiber Saturation Point (FSP -- approximately 25% Oven Dry MC). Above the FSP there is still liquid water in the open cell structure.
The average MC of green Eastern White pine is 68%. You did not indicate which species and each will be different. (Source - Air Drying of Lumber, USDA Forest Service Ag Handbook #402)
From that same reference the air drying time for 4/4 Eastern White pine lumber from green to 20% MC is estimated to be between 60 and 200 days.
Generally mills do not like to saw logs that are too dry. The wood becomes harder as the moisture content decreases and uncontrolled log drying generally causes huge amounts of degrade associated with end checking and splitting. Also if the log is just left to Mother Nature and not kept wet, the entire log would likely be stained (bacterial blue or grey stains). A wet log generally does not have sufficient oxygen within it so the bacteria cannot grow.
The only way to obtain an accurate MC for wood above the FSP is to oven dry it in a forced air oven noting its initial weight and the final weight (determined when additional time in the oven does not change the final weight, thus implying that all the moisture has been removed). The calculation for determining oven dry moisture content therein is:
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