Explain the moisture content of solid wood furniture in detail

There are three forms of moisture contained in wood, one is the water that exists in the cell cavity and the intercellular space, that is, the water that exists in the capillaries, which is called free water. The second type is water that is absorbed by the cell wall, which is called adsorbed water. The third type is the water that makes up the tissue of the cells, known as chemical water.

When the moisture of the moist wood evaporates, the first thing lost is the free water, and the moisture content when the free water evaporates and the adsorbed water is still in a saturated state is called the moisture content of the fiber saturation point.

The fiber saturation point is the turning point of the wood's performance, above the fiber saturation point, the strength of the wood is constant and does not change with the change of moisture content. At the same time, there is no change in the volume of the wood. When the moisture content drops below the fiber saturation point, that is, when the adsorbed water in the cell wall begins to evaporate, the strength increases with the decrease of the moisture content, and the phenomenon of wet expansion and dry contraction is also obvious.

The moisture content of different wood fiber saturation points is about 22% and 33%.

The humidity and temperature in each region of nature are relatively stable in different seasons. When wood is exposed to this relative temperature and humidity for a long time, its moisture content will reach a relatively constant level. At this time, the moisture content is called the equilibrium moisture content (for example, the annual equilibrium moisture content in the Shanghai area.

The equilibrium moisture content of wood varies with the temperature and humidity of the environment in which they are located, and when there is a difference between the equilibrium moisture content and the ambient humidity, the solid wood floor tends to be close to the environment. This results in the phenomenon of wet expansion and shrinkage of wood, which is a physical phenomenon unique to wood.

Wood is another anisotropy. The moisture content of the wood in actual use is below the fiber saturation point, so the gain and loss of water is mainly the adsorption of water by the cell wall. Most of the cells of wood grow longitudinally, and their expansion and contraction are perpendicular to the direction of the cell wall.

As a piece of flooring, we can find that there is generally no expansion and contraction in the longitudinal direction, and the expansion and contraction rate in the width direction is generally 3% 6% (refers to the change of the moisture content of the wood below the moisture content of the fiber saturation point.

It can be seen that it is very important to control the moisture content of the floor. Not only in production, but also in laying, so that the floor is not deformed by moisture.