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Wood - Drying, Moisture and Dimensional Changes


Quiz Questions

1.The amount of moisture in wood is ordinarily expressed as a percentage of the weight of the wood when oven dry.
True
False
2. The oven-drying method has been the most universally accepted method for determining moisture content, but it is slow and necessitates cutting the wood.
True
False
3.The electrical method of determining the moisture content of wood uses the relationships between moisture content and measurable electrical properties of wood, such as conductivity (or its inverse, resistivity), dielectric constant, or power loss factor.
True
False
4.What does ASTM stand for?
American Society for Testing and Materials
American Standards for Testing and Materials
American Standard for Testing and Mechanics
None of the above
5.What does figure 12-1 illustrate about?
(Refer Pg 12-5)
Recommended average moisture content for interior use of wood products in various areas of the United States
Equilibrium moisture content of wood
Recommended Moisture Content
None of the above
6.The main purpose of air-drying lumber is to evaporate as much of the water as possible before end use or transfer to a dry kiln.
True
False
7.In kiln drying, higher temperatures and faster air circulation are used to decrease drying rate considerably.
True
False
8.Water in wood normally moves from high to low zones of moisture content, which means that the surface of the wood must be drier than the interior if moisture is to be removed.
True
False
9.The limitations of air-drying have led to increased use of technology that reduces drying time and introduces some control into drying from green to 20% to 25% moisture content.
True
False
10.A kiln schedule is a carefully developed compromise between the need to dry lumber as fast as possible for economic efficiency and the need to avoid severe drying conditions that will lead to drying defects.
True
False
11.Drying schedules vary by species, thickness, grade, and end use of lumber. There are two general types of kiln schedules: moisture content schedules and time-based schedules.
True
False
12.Most drying defects or problems that develop in wood products during drying can be classified as fracture or distortion, warp, or discoloration.
True
False
13.Distortion is any deviation of the face or edge of a board from flatness or any edge that is not at right angles to the adjacent face or edge.
True
False
14.Warp can be traced to two causes:(a) differences between radial, tangential, and longitudinal shrinkage in the piece as it dries or (b) growth stresses.
True
False
15.Shipping dry means lumber that has been partially dried to prevent stain or mold during brief periods of transit; ideally the outer 3.2 mm (1/8 in.) is dried to 25% or less moisture content.

True
False
16.Air dry means lumber that has been dried by exposure to the air outdoors or in a shed or by forced circulation of air that has not been heated above 49°C (120°F).
True
False
17.Kiln dry means lumber that has been dried in a kiln or by some special drying method to average moisture content specified or understood to be suitable for a certain use.
True
False
18.The normal seasonal changes in the moisture content of interior finish are not enough to cause serious dimensional change if the woodwork is carefully designed.
True
False
19.Flooring is usually dried to the moisture content expected in service so that shrinking and swelling are maximized and buckling or large gaps between boards occur.
True
False
20.When joist hangers are installed, the top of the joist should be above the top of the girder; otherwise, when the joist shrinks in the stirrup, the floor over the girder will be higher than that bearing upon the joist.
True
False