Equilibrium Moisture Content

What is Equilibrium Moisture Content?

Equilibrium moisture content (also known as EMC) refers to the moisture content of wood that stabilizes after a certain period under constant environmental conditions. In this state, the wood neither absorbs moisture from the air nor releases moisture to the air.

Measure humidity | Photo © by Hugo Kämpf

Influencing Factors

The equilibrium moisture content of wood depends on the following factors:

• Relative Humidity (RH): The higher the RH, the higher the wood’s equilibrium moisture content.
• Temperature: As temperature rises, the wood’s equilibrium moisture content decreases.
• Wood Species: Different types of wood have varying equilibrium moisture levels.
• Wood Density: Denser woods generally have a lower equilibrium moisture content.

Significance

Understanding equilibrium moisture content is crucial for the technical use of wood. If the wood moisture deviates from the equilibrium moisture content, the wood may shrink or swell. This can lead to cracks, warping, and shrinkage cracks.

Measures to Achieve Equilibrium Moisture Content

To avoid the negative effects of shrinking and swelling, it is essential to dry the wood to the desired equilibrium moisture content before use. This can be achieved through natural drying or technical drying methods.

In Simple Terms

Imagine wood as a sponge. When the sponge is dry and you put it in water, it absorbs the water. Wood behaves similarly: when in a humid environment, it absorbs moisture. Conversely, in a dry environment, it releases moisture.

See Also:

Wood moisture