Wood, is a porous material that can adjust temperature and humidity. It has high strength, moderate density and hardness. Wood is easy to carry out various forms of machining, and it causes low energy consumption during the process.
However, wood has some shortages. It shrinks when it loses moisture while swells when it gets wet. Also wood has knots and cavities which are natural defects and cannot be avoided.
Wood could be categorized as coniferous and deciduous.
Coniferous: the trunk is tall and straight, with uniform material and good dimensional stability. It is convenient to make large-scale wood board. It is also called soft wood because of the softness.
Deciduous: the straight part of the trunk is relatively short. It has high density, high strength and contains various changes in texture and color. It is also called hard wood.
cross-cut wood board: presents the full pattern of growth rings on the surface, natural decoration.
radial-cut wood board: The direction of the wood grain is basically parallelled. It hardly shrinks or swells and is not easy to warp, which is suitable for furniture structure making
chord-cut wood board: It is more likely to shrink or swell, so the stability is weak. However, the pattern on the surface is extremely beautiful and unique.
Methods of reducing the shrinkage and expansion of woods:
1. Drying: the fresh wood needs to be placed for a period of time or dried by equipment.
2. Surface finishing: paint or wax the wood surface to fill the gaps of the wood and form a protective layer on the surface, making it difficult for moisture and moisture to enter, so as to achieve the purpose of stabilizing the size of the wood.
3. Reserved expansion joint: It is natural that the wood could shrink or swell depends on the moisture. So, leave a 3-5mm expansion joints on the board surface could reduce the cracking and deformation from wood.
4. Veneer: veneer, bamboo skin, and impregnated paper are pasted on the surface of wood products to shield moisture. At the same time, it can increase the decoration, hardness, and comprehensive resistance of wood products
5. Change the natural structure: make some thin wood boards with parallel wood grains, layer them in order of one vertical and one horizontal and glue them together as one artificial wood board. It is also known as Plywood. It can restrict and restrain the shrinkage and expansion of wood, and stabilize the size of wood products.
According to different stress directions, the compressive strength of wood is divided into along-grain compressive strength and cross-grain compressive strength.
Generally, the compressive strength along the grain of wood is larger than the compressive strength across the grain.
Pine is cheap. It is environmentally friendly. The disadvantage of pine is that it is relatively soft, can not bear too heavy weight, and is easy to deform and crack.
Oak includes red oak and white oak. The texture of Oak is natural and clear. It is hard wood, which means that after being made into furniture, it is strong, durable and stable.
Ash wood has high density, high strength, high resistance and not easy to age or deform. Ash wood has good coloring, adhesion and polishing properties.
Cherry wood is a high-grade wood with fine and clear texture, good polishing and good coating effect. It is suitable for high-grade furniture. The disadvantage is that cherry wood is easy to crack and warp, which is not suitable for large-size furniture.
It is precious hard wood with fine and uniform structure, glossy surface and straight texture. It is expensive as well.
Maple is a kind of high-grade wood with beautiful texture, light weight, excellent pattern, and barely has scar knot.
The disadvantage is that the surface of maple is easy to get smooth. At the same time, maple is more likely to warp when it is losing moisture.
- Chapter2.1.Characteristics and functions of wood. Wood and Furniture. Beijing Forestry University on MOOC, 2021.7
- Chapter2.7. Shrinkage and swelling of Wood. Wood and Furniture. Beijing Forestry University on MOOC, 2021.7
- Chapter2.8.Mechanical Strength of Wood. Wood and Furniture. Beijing Forestry University on MOOC, 2021.7
- 12 Types of Wood Commonly Used for Furniture Making by KING COCONUT. http://www.dwywood.com/pc/consultant/1201.html