Wood is the very first material that people have learned to process. Today, houses are built from it, it is used for decoration or furniture. In all these works, such a parameter as the density of wood is important. This is a very unstable value, which depends not only on the tree species, it can vary from one specimen to another over a fairly wide range. In addition, one piece of wood may have different densities. Therefore, all values are averaged.
The different density of wood is explained by the cellular
structure. Wood consists of wood cells of different sizes, shapes, differently oriented in space. All
cell walls consist of one substance with a density of 1540 kg / m
3 , but the structure and size are always different. The density of wood depends on this. The larger the cells, the more porous and light wood, with decreasing cell size, the density increases.
Within one species of trees, the specific gravity may vary depending on the place of growth. For example, a tree grown in an arid region will have a higher density of wood than one that grew in a swamp. This parameter also depends on age: the older the plant, the denser its wood.
To a certain extent affects this indicator and humidity. The more water the cells contain, the heavier they are. But since this indicator changes rapidly, all data are usually given at a certain humidity. How hard or easy it will be to process the material also depends on an indicator such as wood density. The table in which the averaged results of practical measurements are entered must necessarily contain an indication of humidity for which values are given.
To achieve optimal density, a technique such as drying is used. There are two types of this process: natural and technical. During natural drying, the materials are stacked in ventilated stacks that dry under the influence of natural conditions. During technical drying, the wood is placed in specially equipped drying chambers in which certain humidity and temperature are maintained. In such chambers, the wood is brought to the required moisture content.
Depending on the density, the wood can be divided into:
- light (pine, poplar, cedar, linden);
- medium (elm, beech, ash, birch);
- heavy (maple, hornbeam, oak).
With increasing density, the
mechanical properties of wood also change
: its tensile and compression strengths increase. The denser the wood, the easier it is to process it. Therefore, pine, whose density is low, is used more often for construction or for rough carpentry, and oak, which has a high density, is considered one of the best carpentry species. Although good products can also be made from pine, the denser oak wood looks much more attractive, and oak products last much longer, chips and dents appear on them less often. Using pine products, you need to be extremely careful: any mechanical impact can leave a mark. But dense wood is poorly impregnated. For example, pine is easier to treat with antiseptics than oak. However, dense wood is less susceptible to abrasion, which is important for stairs, railings and floors. The task of what type of wood to use in certain jobs is up to you, but all factors must be taken into account.