### What is Moisture Content in Wood?
Wood moisture content (MC) refers to the amount of water present within the wood compared to its dry weight. It plays a crucial role in the properties and performance of wood, influencing its strength, durability, and susceptibility to decay.
When wood is cut and harvested, it typically contains a high moisture content, which can exceed 100%. As it dries, the moisture content gradually decreases, eventually reaching an equilibrium moisture content (EMC) that is stable for the surrounding environment. EMC is typically between 6% and 12%.
### Significance of Moisture Content
Moisture content in wood significantly affects its:
– **Structural integrity:** High moisture content can weaken wood, making it more susceptible to bending, twisting, and warping.
– **Dimensional stability:** As wood dries, it shrinks, which can cause distortions and cracks. Controlling moisture content helps maintain dimensional stability.
– **Durability:** Higher moisture content makes wood more vulnerable to decay, rot, and insect infestation. Optimal moisture content ensures longevity and resistance.
– **Heat insulation:** Wood with lower moisture content is a more effective insulator, providing better thermal performance for buildings.
– **Fire resistance:** Moisture acts as a natural fire retardant. Wood with higher moisture content is less likely to ignite and spread flames.
### Measurement of Moisture Content
Various methods exist for measuring wood moisture content:
– **Gravimetric method:** Drying a wood sample to determine the weight loss due to evaporation
– **Electrical impedance method:** Measuring the resistance of wood to an electrical current
– **Capacitance method:** Detecting changes in capacitance between electrodes inserted into the wood