Before wood became a source of foreign exchange today, cavemen had learnt how to cook with it. But it didn’t just stop there.
As years passed and civilisations evolved, people began using wood for many things. Today, wood is used to make furniture, windows, books, bridges, and much more. Wood is so versatile that you would have wondered what this material is made up of? What are its characteristics? Why is wood so popular? We are going to provide answers to these questions and tell you why wood is so famous. So read till the end of this article to discover these answers.
WHAT IS WOOD?
Wood is an organic material, meaning it comes from nature. It is that hard substance that comes from trunks and branches of trees.
STRUCTURE OF WOOD
The first part of a tree you’re likely to see and touch is the bark. Peel off that bark and what you will find is two kinds of wood. The first is a moist, light, living layer called the sapwood. The sapwood has tubes called xylem that act as the tree’s circulatory system, moving water and nutrients up from its roots to its leaves. If you dig past the sapwood, you will find a much harder, deeper part of the tree. This is the heartwood, where there’s no sign of life. Water and nutrients never get here because the xylem tubes that transport them have been blocked up with resins or gums and eventually stopped working.
Around the outer edge of the sapwood and trunk, is a thin active layer known as the cambium that is responsible for the secondary growth of stems and roots in the tree. Secondary growth happens after the first season.
You will also find knots in trees. When dead branches fall off a tree, wood knots appear in the area where the branches have died. They are visible and often darker than the surrounding area.
TYPES OF WOOD
We have two types of wood: Hardwood and Softwood. Often, people misinterpret the meaning of these terms. We have cleared them here for you.
Hardwood is a type of wood you only get from deciduous trees. These trees are known to have wide or broad leaves and may drop their leaves every fall. Examples are ash, birch, beech, mahogany, maple, oak, teak, and walnut.
Softwood, on the other hand, comes from coniferous trees. Some of these trees have cones and needles which are retained all year round. They are called gymnosperms. Examples of softwood trees are cedar, cypress, fir and redwood.
Generally, most people believe that hardwoods are harder than softwoods.
Though this is true in most cases, it isn’t entirely. For instance, Balsa is a hardwood that is actually very soft.
Chemical composition of wood
Trees are living things. And like living things, wood in trees is made up of cells.
These cells are made up of three substances, which are cellulose, lignin and hemicellulose. Cellulose makes up 50 percent of these cells, while lignin makes a fifth to a quarter of in hardwoods and a quarter to a third in softwoods. Hemicellulose takes up the rest.
STRENGTH OF WOOD
When handled, wood is strong and stiff. But when compared to other materials like steel, it’s flexible and lightweight.
Unlike metals and plastic which have a fairly uniform inner structure that makes them isotropic (behaving the same way in all directions), wood is different. Because of its annual-ring-and-grain structure, you can bend and snap a small, dead tree branch. However, it’s almost impossible to compress or stretch that same branch as you would do with a plastic water bottle.
Likewise when you try cutting wood with an axe. The wood splits easily when you drive the axe’s blade along the grain of the wood but is difficult when you do it through the grain. This weird structure is why wood is referred to as anisotropic — it has distinct properties in different directions.
Having this in mind is also important when you consider using wood as a construction material. For instance, if you’re going to support a traditional wooden building with wood, make sure the poles are erect so that the building can rest above it. It is better this way because the weight of the house is transmitted down into the ground, along the wood’s length parallel to the grain.
Plus, wood is hardly compressed when done that way due to its high compressive strength. But when placed horizontally, these wooden poles will bend or break without any support because they have lower tensile strength. That is, they have a low resistance to bending.
Some like the famous oak have a higher tensile strength though, meaning they can withstand bending under high pressure. It is for this reason they were widely used to make heavy, horizontal beams in old buildings.
If there is a material that has passed through many generations and still looks beautiful under good care, it’s wood. Some last thousands of years, and some hundreds. Many outlive their makers or buyers and are inherited by their children. A good example is a piano. That said, wood can also damage naturally. Organisms like fungi and termites are usually responsible for this, nibbling away the wood’s cellulose and lignin and eventually reducing it to dust.
WOOD AND ENERGY
Wood has amazing properties. For example, they are a good source of heat and warmth. It is this reason you feel so warm inside a wooden house during a chilly day. The wood acts as a good heat insulator.
Also, wood is a good sound absorber. It shuts out sound completely, especially in noisy places. But they can also be designed to amplify sounds like the guitar or piano to make music. There’s more!
Wood is a bad conductor of electricity, while dry wood has low resistance to fire and burns more easily than wet wood.
Wood and the environment
These days everybody is talking about using things that help our environment, including our government. Wood is one of those materials that actually helps us to live well. Unlike plastics and other end products of petroleum that pollute our environment and cause climate change, wood is nothing like that. It is also a sustainable material. That means for as long as we live, we will always have trees that we can use to make many things — as long as we replant the one we cut down.
Though replanting of trees may be good for the environment, a brand new tree has much less ecological value compared to the one that’s been living for years. Similarly, logging damages the environment too, together with some of the chemicals used to speed up the growth of new trees and process the wood in trees to make wooden products.
Another good thing about having trees around is that they are home to many of the world’s animal populations.
Why is wood such a popular material?
Apart from the fact that it is a natural resource, economically feasible, and readily available, producing and processing wood consumes less energy than most building materials. Plus, it is a perfect substitute for materials made from fossil fuels that pollute our environment.