Wood is the very first material that people have learned to process. Today, houses are being built from it, it is used for finishing premises or making furniture. In all these works, a parameter such as the density of wood is important. This is a very unstable value, which depends not only on the species of the tree, it can vary from one specimen to another in a fairly wide range. In addition, a different density can be in one piece of wood. Therefore, all the 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 a single substance with a density of 1540 kg / m 3 , but the structure and their dimensions are always different. The density of wood depends on this. The larger the cell, the more porous and light the wood, with a decrease in cell size, the density increases.
Within a single tree species, the specific gravity may vary depending on the place of growth. For example, in a tree grown in an arid region, the density of wood will be greater than that of the one that grew in the swamp. This parameter also depends on age: the older the plant, the denser its wood.
To some extent, this indicator and humidity. The more water the cells contain, the heavier they are. But since this indicator varies rapidly, all data are usually given at a certain humidity. The extent to which it is difficult or difficult to handle the material, also depends on such an indicator as the density of wood. The table, in which the averaged results of practical measurements are recorded, must contain an indication of the humidity for which the values are given.
To achieve the optimum density, a technique such as drying is used. There are two types of this process: natural and technical. When natural drying, materials are piled in ventilated piles that dry under the influence of natural conditions. In technical drying, wood is placed in specially equipped drying chambers, in which a certain humidity and temperature are maintained. In such chambers, the wood is brought to the required humidity.
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 compressive strength increases. The denser the wood, the easier it is to process it. Because the pine, the density of which is small, is used more often for construction or for rough carpentry, and oak, which has a high density, is considered one of the best carpentry. Although it is possible to make good products from pine, but more dense oak wood looks much more attractive, and oak products serve much longer, chipped and dented less often. Using the same products from pine, you need to be extremely careful: any mechanical impact can leave a trace. But dense wood is poorly impregnated. For example, it is easier to treat antiseptics with pine than oak. However, dense wood is less prone to abrasion, which is important for stairs, railings and floors. The problem of what type of wood to use in these or other works, you decide, but you need to consider all factors.