Wood classification: hardness, growth environment and application areas

Wood plays an important role in construction, furniture and handicraft production. Hardness, grain and application are often decisive factors when selecting wood. This article looks at the classification of wood by hardness, examines the properties, growing environments and best uses of different types of wood, particularly teak and suar wood (also known as acacia wood or licorice). It also introduces the common softwood species used for furniture in Europe and their advantages and disadvantages.

1. Classification of wood according to hardness

The hardness of wood is usually measured by the Janka hardness test, which measures the force required to press a steel ball into the wood. According to the hardness, wood is roughly divided into hardwood and softwood:

• Hardwood : Usually comes from deciduous trees, grows more slowly and has a denser wood structure. Typical hardwoods are teak, oak, walnut and acacia.
• Softwood : Usually comes from coniferous trees, grows faster and has a softer wood structure. The most common softwoods include pine, spruce and cedar.

2. Teak wood (Teak)

a. Hardness and properties
Teak is a very hard hardwood with a Janka hardness of about 1,150 pounds-force (lbf). This wood contains natural oils that make it particularly water-resistant and resistant to rot. Teak has a golden-brown hue and a unique grain that makes it a preferred choice for furniture and exterior construction.

b. Growth environment and reason for formation
Teak grows mainly in Southeast Asia, particularly in Myanmar, Thailand and Indonesia. The teak tree (Tectona grandis) prefers tropical climates and often grows in monsoon forests. This environment allows the teak to absorb plenty of sunlight and water, which helps form its wood structure. The rich natural oils in the wood not only strengthen its durability but also provide natural protection against insects and rot.

c. Areas of application
Thanks to its durability and weather resistance, teak is often used for outdoor furniture, decks, shipbuilding and high-end interior furniture. Teak's natural oils also prevent warping and cracking, making it ideal for use in humid environments.

3. Suar wood (Suar or Acacia)

a. Hardness and properties
Suar wood has a Janka hardness of about 1,000 pounds-force (lbf), slightly less than teak but still in the hardwood category. Suar wood is known for its unique grain and color variations, which typically blend light and dark tones, creating a natural beauty.

b. Growth environment and reason for formation
The suar tree (Samanea saman), also called the rain tree, is widespread in South America, Africa and the tropical regions of Southeast Asia. This type of wood grows relatively quickly, has a strong trunk and a distinctive grain. Suar trees thrive in tropical and subtropical humid environments. The rapid growth leads to a higher wood density and a solid wood structure.

c. Areas of application
Suar wood is often used to make dining tables, desks and art carvings. The unique grain gives each piece of furniture a natural artistic touch. In addition, the sturdiness of suar wood makes it ideal for load-bearing furniture such as bed frames and large tables.

4. Advantages and disadvantages of common softwoods for furniture in Europe

In Europe, softwood is often used to make inexpensive furniture. Although softwood is less hard than hardwood, its lightness and ease of work make it the preferred choice of many furniture makers. Here are some common European softwood species and their advantages and disadvantages:

a. pine
Hardness and properties:
Pine is one of the most commonly used softwoods in Europe, with a Janka hardness of about 380 pound-force (lbf). Pine is relatively soft, easy to work and carve, but tends to be easily damaged or scratched. It is usually light yellow in color with natural knots and a relatively even grain.

Growth environment and reason for formation:
Pines grow widely in the temperate and colder regions of Europe and are very adaptable. Their rapid growth rate results in a loose wood fibre structure that is not particularly hard but allows for large-scale cultivation and harvesting.

Advantages and disadvantages:

• Pros: Pine is inexpensive, easy to work with, and has a warm color. It's good for kids' and budget furniture, as well as DIY projects.
• Disadvantages: Pinewood is less durable, susceptible to scratches and impacts, and tends to swell or crack in humid environments.

b. Spruce
Hardness and properties:
Spruce wood has a Janka hardness of about 510 pounds-force (lbf), making it slightly harder than pine. Spruce wood has a good strength-to-weight ratio, a pale white to light yellow color, and a straight, fine grain.

Growth environment and reason for formation:
Spruce trees grow in the mountainous regions of Europe, especially in the Alps and on the Scandinavian Peninsula. Spruces grow quickly, so their wood structure is rather loose, but the long wood fibers increase their strength.

Advantages and disadvantages:

• Advantages: Spruce wood is light, relatively strong and is often used for building structures and the construction of musical instruments (e.g. piano keyboards). It is also a good choice for garden furniture.
• Disadvantages: Like pine, spruce is less durable and the surface is prone to scratches. Therefore, it is less suitable for furniture that is used frequently.

c. Cedar
Hardness and properties:
Cedar wood has a Janka hardness of about 350 pounds force (lbf), making it one of the softer softwoods. Cedar wood is particularly notable for its natural pest resistance and aromatic scent, making it ideal for making chests, wardrobes, and outdoor furniture. Cedar wood varies in color from light red to dark brown and has a relatively even grain.

Growth environment and reason for formation:
Cedar trees grow in Mediterranean climates as well as in North America and prefer dry, sunny environments. The fiber structure of cedar wood is relatively loose, but the natural oil makes the wood resistant to pests and rot.

Advantages and disadvantages:

• Advantages: Cedar wood is highly resistant to pests, has a pleasant smell and is ideal for making cabinets, wardrobes and other pest-resistant furniture. It can also be used outdoors.
• Disadvantages: Cedar wood is soft, so it is prone to scratches and dents and is generally not used for furniture that will be subject to heavy use.

5. Other common hardwoods

a. Oak
Oak wood is one of the most common hardwoods. It is characterized by its wear resistance and strength and is often used for flooring, cabinets. Its light yellow to reddish brown color also makes it ideal for decorative items.

b. Walnut
Its dark color and fine grain make it popular for musical instruments and carvings. The strength and toughness of walnut also make it well suited for complex handicrafts and decorative materials.

c. Maple
Maple wood is one of the harder hardwoods. Maple wood is often used to make gym floors and musical instruments (e.g. guitars and pianos).

6. Conclusion

The hardness, grain and color of wood determine the areas in which it is used. Hardwoods such as teak are ideal for garden furniture and shipbuilding due to their excellent weather resistance and rot resistance. Suar wood, on the other hand, has a beautiful grain and medium hardness and is ideal for making tables and handicraft pieces. In Europe, softwoods such as pine, spruce and cedar are often used to make inexpensive furniture. Despite their lower hardness, softwoods have a place in many furniture and construction projects due to their lightness, ease of workability and natural properties.

Understanding the classification and properties of wood can help us choose materials and not only improve the aesthetics of our living space but also extend the life of objects.