Woods, Soft & hardwoods, Things to consider, Steam bending & Laminating

Woods

A lumber is a tree that has just been felled, i.e. just after it has been cut down in the forest. The definition of a timber is a wood that's been cut down and processed. This is the next stage from the tree being cut down. You can tell how old a tree is by looking at its anual rings, which are the circular shapes seen when looking directly down at a cross section of the tree. One of these rings is equivelant to one year of growth. Fibres in the trunk run parallel to the annual rings, so the wood can be called 'fiberous'. Another point to note is that 58% of a tree is cellulose and 28% us resin, which protects the tree.

Softwoods & Hardwoods

There are two types of wood, soft and hard woods. Hardwoods generally take longer to grow, and are more dense and robust. Softwoods are more readily available, and some of its species are fast growing. Some examples of hardwood are ash, oak, beech, teak and walnut, and some examples of softwoods are larch, spruce, scot's pine and douglas fir. Hardwoods come from deciduous trees, in the autumn these trees change colour and lose their leaves. Softwoods come from coniferous trees, i.e. trees with needles or cones.

When these woods are cut down as lumbers, they are 70% moisture. In order to dry the wood, there are two main processes used. You can either air dry the material or kill dry it. Air drying is literally stacking the wood and then leaving it for several years. The moisture will evaporate out of the wood and, eventually, leave the material completely dry. Kill drying is leaving a load of wood in an oven - this takes only a few hours as opposed to air drying. However, this is obviously a lot more expensive than air drying.

Things to consider when chosing a wood

There are many factors you need to consider when chosing a wood for a particular job, such as:
- Physical strength: how strong and rigid the wood needs to be
- Aesthetic properties: how the wood looks, e.g. the grains, etc
- Moisture properties: is the wood completely dry for use?
- Protection: for example, varnishing a wooden bench for outdoor use
- Operating conditions: Any particular features of the environment or product the wood's being used in or for
- Costs: How expensive and affordable the wood is, and which is the cheapest wood of that range?
- Sustainability/environmental issues: Consider how many trees are being cut down, as well as the FSC: Forestry Stewardship Council
- Size of boards available: Is there a board of wood big enough for the job or product needed?

Steam Bending

This process is used to bend woods using the pressure and heat from steam. It takes sometimes several hours but gives an end product of a high quality and a good shape.
However, only bentwood can be used in this process. This it because the primary attribute of bentwood is that its grain runs continuously along its entire length and not in any other direction. If the bend is made across more than one axis then the timber will be twisted to align to the grain, so the process will not work. The main advantage bentwood has over other types of wood is its strength, as it won't snap after being bent or under the pressure during the process.
It takes around one hour to steam bend 25mm of ash, and ash is the most common wood used in steam bending.

Laminating

The definition of a laminate is something that is built up in layers. A lamination is the process of joining the layers together. This is a widely used process in industry as it strengthens and thickens a material, and also allows different materials to me mixed into one. For example, plastic laminate is made of composite layers of paper and plastic.

An alternative way of bending wood to steam bending is lamination. There are two main methods of how to laminate woods:
- Laminating using a male & female mould.
- Laminating using a vacuum bag or vacuum frame.