1. The source and state of moisture in wood
When a living tree grows, its roots continuously take in water from the earth, and the xylem of the trunk transmits water to different parts of the tree. At the same time, the phloem of the trunk transports nutrients made by leaf photosynthesis to different parts of the tree. part. The most crucial element for tree growth is moisture, which also serves as a vehicle for the transportation of other chemicals by trees. The majority of the moisture in the wood is still present after the living tree is felled and sawed into different-sized planks. During storage, shipping, or use, wood will also take some moisture into its inside.
The amount of moisture in the xylem in a tree's trunk varies depending on the species. In different growing seasons, even the same tree's xylem has a varying water content. The distribution of water in wood is relatively unequal because different xylem components, including heartwood, sapwood, roots, trunks, and treetops, have varied water contents. The moisture content of the wood will change as the surrounding atmospheric conditions do. Due to its various locations in the wood, the moisture can be classified into three types: free water, absorbed water, and mixed water.
(1) The enormous capillary system made up of the pits on the wood cell wall or the perforations at the catheter's tip, the cell cavity, and the intercellular space contains free water. Physically, the free water and the wood are united, but the fusion is loose. quickly escapes from wood and is also simple to breathe in. Free water is the first item to evaporate when wet wood is exposed to dry air. The free water content of various tree species varies substantially in newly felled wood, often ranging from 60 to 70% to 200 to 250%.
(2) Absorbed water is either adsorbed on the free control group of cellulose molecules on the surface of the crystallite and in the amorphous region, or it is present in the microcapillary system created between the microfibrils and big fibrils in the wood cell wall. The greatest amount of water sorbed in wood is often between 23 and 31%, with an average of roughly 3%. The amount of water sorbed in wood varies slightly between tree species. The material of the wood is relatively closely coupled with the absorbing water, making it difficult for the water to escape from the wood.It can only be removed once the wood's free water has evaporated and the partial pressure of water vapor inside the wood is larger than the partial pressure of water vapor inside the adjacent wall. Wood evaporation.
(3) A strong chemical connection exists between the components of the cell wall and the combined water. This portion of the water content in the wood is very little and can be disregarded. Under typical drying conditions, it cannot be eliminated.
2. Indoor air quality and wood moisture
It is particularly advantageous to both human health and the preservation of goods for the humidity in the indoor environment where people reside to be steady within a specified range. According to studies, the following relative humidity ranges are necessary to prevent damp mold: 0-80%; 0-70% or 80-100%; 40-60%; 55-60%; and 40-60% to preserve books from bacterial infection and death. The relative humidity in the area where people live should be between 60 and 70 percent at the lowest rate.
There are a variety of elements that affect interior humidity, including changes in outside temperature as well as changes inside, water vapor entering or leaving through transoms or ventilation openings, water vapor moving through walls, water vapor entering from the kitchen, etc. Humidity changes may also result from it.
One of wood's special qualities is its ability to regulate humidity, which also makes it a good choice for furniture and interior décor. Homes decorated with wood or other natural materials experience a far greater shift in humidity than homes made of concrete or wallpaper. Small. The moisture absorption and desorption of the wood itself, which directly reduces the humidity variations in the indoor environment, is the basis for the so-called humidity-controlling properties of wood. The water vapor partial pressure balance between the indoor environment and the wood is disrupted when the relative humidity of the indoor environment falls.The moisture inside the wood will escape because the partial pressure of water vapor inside is higher than that of the indoor environment. The desorption process results in a rise in the relative humidity of the interior environment. Contrarily, the wood will absorb moisture from the indoor air through a process known as moisture absorption as the relative humidity of the indoor environment rises.A new dynamic equilibrium is attained after a very strong initial phase of the wood desorption or hygroscopic process. People have long been accustomed to living in an atmosphere with wooden furniture and wooden interior design elements, where wood serves as a moisture storage agent and a natural regulator of indoor air humidity.
