Moisture content in wood causes what kind of changes?

• A. Color change only
• B. Dimensional instability and fluctuations of weight
• C. Increased hardness
• D. Permanent deformation only when wet

Answer: (B)

Wood is hygroscopic, so changes in moisture content cause the wood to move and gain or lose weight. When moisture rises, wood fibers absorb water and swell; when moisture falls, water exits and the wood shrinks. This leads to dimensional instability—changes in size and shape that aren’t uniform, often more across the grain than along it. At the same time, moisture content directly affects mass, so the wood’s weight fluctuates with moisture uptake or loss. Color changes can occur with moisture, but they aren’t the universal or defining effect; hardness typically decreases as moisture increases, and permanent deformation isn’t guaranteed simply by being wet. The primary consequence tied to moisture content, therefore, is the combination of dimensional changes and weight changes.