How its made – Wood
While browsing our selection of storage sheds, you might be thinking about what you want from a wheelie bin store, rather than about the product itself. They look nice, and they do their job, but have you thought about the raw materials that are used to make them? Here’s everything you need to know about the natural wonder that is wood.
What is it?
Everyone knows that wood comes from the trunks and branches of trees. If you peel off the bark of a tree, you will find 2 kinds of wood. Closest to the tree’s surface, there’s a moist layer called sapwood. This contains tubes called xylem, which carry water and nutrients from the tree’s roots to the leaves. If you go deeper inside the tree, there’s a dead, harder part of the tree. This is known as heartwood.
Around the edge of the sapwood, there’s a thin layer called the cambium, where you can see the rings that appear each year to indicate how old a tree is. You can see these when a tree is cut horizontally. If you cut it vertically, you will see the xylem (nutrient and water tubes) which you may know better as the grain of the wood.
Hardwoods and softwoods
Wood is divided into two types; hardwood and softwood. The names aren’t related to how tough the wood is however.
Hardwood comes from trees that lose their leaves in the autumn, such as ash, beech, maple, and oak trees.
Softwood comes from evergreen trees, such as fir trees, pine, and redwood trees.
Hardwood has attractive looking grains, so it tends to be used to make furniture, whereas softwood comes from taller, straight trees, so it is often used in construction.
How strong is wood?
Wood is strong and stiff, but when compared to other materials, like steel, it’s light and flexible. Also, a material like steel has a standard inner structure; it behaves the same way. However, it is pushed, pulled, or twisted. Wood doesn’t because of the grains and the ring-like structure it has. For example, wood will split easily when chopped with an axe along its grain, but it is very difficult to cut through the grain.
The strength of wood is important for construction projects, as wooden buildings tend to be supported by big vertical poles that transmit forces along their length, running parallel to their grain. Positioning wood vertically is ideal because it can withstand a lot of compressions when it is loaded this way. Wood is much weaker when it lies horizontally because they lack resistance to bending across the grain.
However, the strength of different types of wood can vary, and Oak has one of the highest resistances to bending. This is why it was used in the beams in very old buildings.
How durable is wood?
This really is one of its strong points. Archaeologists have found remains of wooden items that have been proven to be thousands of years old. As long as wood is correctly preserved it will last for a very long time. It is a natural material though, so it is always going to be at risk of rotting, being infested with termites, or disease.
Wood and water
Pretty much all wood soaks up water like a sponge, and that’s why it tends to swell up in damp conditions. Wood absorbs water so easily because a tree is designed to carry water right from its roots to its leaves. Some types of wood soak up many times their own weight in water.
Wood is a good insulator
Wood is a good heat insulator, but dry wood does burn easily. It also absorbs sound well, but it is a poor conductor of electricity.
Wood is environmentally friendly
Wood was one of the first natural materials that people ever used. It is potentially sustainable, because if new trees are planted to replace those that have been cut down, you could go on using wood without harming the planet. It’s important to replace trees, as they absorb carbon dioxide and slow down the climate change process. They also provide habitats for wildlife.
But in reality, forestry can be very damaging to the environment, not only because of the cutting down of the trees, but consider the chlorine which is used to bleach wood that is going to make paper; it can get into rivers and cause pollution.
Harvesting wood
Wood is like a crop, but what makes it different from other crops is that trees take so long to grow. A tree can take decades to reach maturity. The harvesting process depends on whether a tree is growing in a plantation of similar species of a similar age, or whether it’s in a forest along with a mix of species of different ages.
Some fast-growing trees can be cut down all at once if they are being used as biofuel. Individual trees can be felled and carried away by truck or even a helicopter if the forest is at altitude.
Sometimes bark and small branches are removed before the trees are taken for processing, though sometimes this can be done off site, depending on how far away the processing site is and how valuable the wood is.
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