Measuring Moisture Content in Wood Log/Trunk 1

[yjwong]

I am researching on a way to measure the moisture content (MC) in the wood log/trunk as supplied but yet still struggling to find a best solution. I want something quick and effective, such as an electrical moisture meters but have not found an appropriate meters for such application. Can anybody please help?

 

[ornerynorsk]

A typical moisture meter will read to 40-50% or more.

 

[ornerynorsk]

McMaster Carr has them, but I would think that any forestry supply would have what you need.

 

[boo1]

You have to know if you have a US style moisture meter or European style. European moisture meters (Gann, etc) are calibrated to read across the grain and US meters are calibrated to read along the grain. Across grain readings are impossible from the edge. At very low MCs (under 12% MC), pin orientation will not affect the readings. When going into the lumber from the edge, go at the thickness midpoint if you want the core, and use the 1/4 points for average values.

Consider researching:
ASTM D4442
Direct Moisture Content Measurement of Wood and Wood-Base Materials

ASTM D1037 (Part A, Sec. 126-127)
Evaluating the Properties of Wood-Base Fiber and Particle Panel Materials, Part A, Sec. 126-127: Moisture Content and Specific Gravity

Drying Oak Lumber by Eugene M. Wengert
Department of Forestry
University of Wisconsin
Madison, WI
Cost: $25 plus $5 postage and handling (plus WI residents add $1.65 tax)
Payment: Check, money order, P.O.
Order from:
Department of Forest Ecology and Managemen
1630 Linden Drive
University of WIsconsin-Madison
Madison, WI 53706

Also search the archives for a site at the US Forest Products Lab.

 

[JAE]

I have no serious expertise here - but would it be possible to take a sample, weight it, find its volume, and then dry it out in a kiln and re-weigh?

 

[yjwong]

That's indeed the most reliable way I know (oven weighting) but it takes time and too much effort which we could not justify the cost. So we need something else quick and effective, such as electric meters. The thing is there's too many choices in the market which can be quite confusing.

 

[boo1]

ASTM D4442 lists four methods of determining moisture content, two of these are the oven-drying and the electrical methods. "The oven-drying method has been the most universally accepted method for determining moisture content, but it is slow and necessitates cutting the wood. Oven drying is too slow and cumbersome for inspection, so portable moisture meters were developed. The electrical method is rapid, does not require cutting the wood, and can be used on wood in place in a structure. However, considerable care must be taken to use and interpret the results correctly."

The principal advantages of the electrical method compared with the oven-drying method are speed and convenience. Only a few seconds are required for the determination, and the piece of wood being tested is not cut or damaged, except for driving electrode needle points into the wood when using conductance-type meters.

see links

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm

(ch12)

http://www.fpl.fs.fed.us/documnts/pdf1994/james94a.pdf

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr06.pdf

http://www.fpl.fs.fed.us/documnts/fplrn/fplrn008.pdf

 

[yjwong]

That's very helpful, thanks a lot. Just wonder if there's any chance you will have the related ASTM document? As I'm not able to access from my university network now so downloading the document cost me some fortune. Thanks again for your help boo1, and all the guys!

 

[boo1]

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