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Woods are fibrous materials made up of an arrangement of plant cells and resins. Paper and card are derived from wood and therefore share the same molecular structure.
Wood and timber can be put into three categories:
Wood and timber can be put into three categories:
Boards made from wood pulp, chips or layers: Chipboard, Conti board, MDF, Plywood, Stirling board
Woods can either be deciduous or coniferous.
Deciduous trees
Deciduous trees
Have broad green leaves which are shed in theautumn in a temperate (different seasons) climate. These are known as Hardwoods. Hardwoods grow in warm countries such as Africa, Asia and India and can take 100 years or more to mature, although there are faster growing hardwoods.
In tropical countries such as Thailand hardwoods often do not shed their leaves as there is often no noticeable change in the seasons like there is in the UK.
coniferous trees
coniferous trees
Have needle type leaves which stay on the tree all year round which is why they are known as Evergreens. These are Softwood trees. They generally grow in colder countries such as Russia and Scandinavia and take around 20 years to mature.
The UK has a temperate climate which is why so many different types of tree grow there and why some lose their leaves in winter.
Deciduous conifer - Larch
Deciduous conifer - Larch
'Siberian Larch timber is a softwood that comes from a tree native to western Russia and that cold climate leads to a timber that is more durable than many other softwoods, with a natural resistance to decay.'
Anatomy of a tree
Anatomy of a tree
Trees grow from the outside inwards making a new layer each year (hence annual rings). As a result the weakest wood is just inside the bark while the heartwood is the most stable and dense section of the tree. Eventually the heartwood may begin to die and is know as deadwood.
Wood Conversion
Wood Conversion
In order to use wood we inevitably need to cut down trees!
Trees are cut a few feet from the ground leaving a stump with the roots still attached in the ground as it is much too hard to dig them up.
However, some trees can re-grow from their stumps and the process of doing this on purpose is known as coppicing.
The trees then have their branches removed and these are then chipped and used to make chipboard, paper and other wood-based products.
Where the branches join the trunk, they leave a knot (a defect).
We are then left with the tree trunk ready to be converted into usable wood.
Conversion of timber
Conversion of timber
As soon as possible after felling the tree should be converted into usable timber. Natural wood is only available at the maximum width of the tree it came from!
Stock forms of timber
Stock forms of timber
Wood can be obtained in a variety of forms from the raw material (the tree itself) to various shapes and sizes of processed timber.
However, a single piece of wood can be no bigger than the tree it comes from unless it is engineered or laminated.
Common forms include: planks, beams, square and rectangular section, dowel and various manufactured boards which are usually available in sizes up to 2400mm x 1200mm (sometimes even larger). Wood can also come in mouldings or profiles, which are commonly used for decorative features in rooms.
Planks, beams, square & rectangle section
Dowel
Manufactured boards
Mouldings or Profiles
Facts about trees
Facts about trees
A collection of trees is called a forest and forests cover 30% of the earth.
There are around 3 trillion trees with most in tropical countries. That’s around 400 trees for every person...
...BUT...12,000 years ago there were twice as many trees and we are cutting down millions of trees every day.
Trees convert carbon dioxide (our bad breath) into oxygen which all humans and most animals need to survive.
They provide materials for building.
Pulp from wood is used to make paper and card.
They provide food for humans and animals; nuts and fruit.
Trees provide shelter for humans and habitats for animals and birds.
The wood can also be burnt for fuel.
Replanting two trees for every one that we cut down will help to replace the dwindling tree population on the earth.
Using alternative materials may reduce deforestation but may cause other ecological problems such as use of fossil fuels, mining for ores etc.
Trees are a sustainable and renewable source of energy and materials.
Sustainable means we can keep supplies of a material going by recycling, repairing or reusing them.
Wood is sustainable but it is also renewable because we can grow more.
In contrast, metal and polymers (other than bioplastics) are not renewable as their sources (ores and oil) are finite (running out) and you cannot make more. Other than recycling metal and plastic, when they run out they are gone forever!!
In order to make sure we have enough wood we have a system of replanting which means that for every tree we cut down we plant two more. We have been doing this for around 50 years now but we are nowhere near replacing all the trees we cut down over thousands of years.
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