- Its heterogeneity: Because of the uniqueness of its growth, wood is made up of different-shaped cells of variable density.
- Its anisotropy: The cell structure of wood is directionally oriented.
- Its hygroscopy: Based on the ambient humidity and temperature, the moisture rate of the wood can increase or decrease.
- Its retractability: Based on its moisture rate, wood can increase or decrease in size.
The unique features of wood
Besides these intrinsic characteristics, wood is a plant organism, and as such, many parameters can affect its maturity: humidity, sunlight, pollution, the regional climate, the nature of the soil… all of which have a strong influence on the way the wood grows. And like every other natural material, wood has unique features that must be considered by those who work with it. Among these, the most common ones are nodes (due to the presence of branches during the growth of the tree), splits (generally due to the felling of the tree and the drying of the trunk), and irregularities in the grain (in other words, the presence of fibres going in different directions). Synthetic woods – such as particleboard, chipboard, and plywood – are considered “inert” materials and are therefore easier to work with. In this case, there’s no need to worry about the direction of the fibres or the growth. However, other constraints must be taken into account, such as the presence of agglutinating resins and glues that help hold the fibres together.
Along the grain, across the grain
The properties and the processing method of the wood are dictated to a large extent by the arrangement of the wood fibres – in other words, what we call the “grain.” When it’s a small section, “along the grain” wood (in other words, cut lengthwise in the direction of the fibre growth) is suitable for working in traction. However, if it’s a bigger section, it can be worked in flexion. “Across the grain” means that the wood has been cut perpendicular to the wood grain. This type of wood is less resistant to traction and flexion; however, it’s much more resistant to compression.
Woodworking is done using specific machine tools which are nevertheless similar in their design to the machine tools used in metal machining. However, these machines use lighter, less invasive tools. Among the most commonly used machine tools are the wood lathe, the mortising machine (used to create mortises, the holes designed to receive tenons), the milling machine, and the drill. Extremely versatile, wood is suitable for all sorts of applications, such as furniture, creative arts and crafts, architectural models, interior design, toys, as well as the naval and aviation industries.