Post 217 ⇒ by Gautam Shah
Wood’s appearance, warmth to touch, its ability to be worked with simple inexpensive tools, wide range of tonal hues, grain patterns and textures make it, the most versatile craft material. The only drawback for using wood, is the effect of moisture on its structural properties and its susceptibility to decay. No two pieces of timber are similar, the great variations in structural properties, colour, texture etc., make it suitable for different uses. These wide variations in a quality put the timber to a disadvantage in comparison to many naturally available materials.
Trees can be basically classified into two groups – exogenous trees (exogens) and endogenous trees (endogens).
- Trees may be broadly grouped into exogenous and endogenous trees according to the way in which their stem diameter increases.
- Endogenous: are trees with inward growth, and have longitudinal fibres such as canes, bamboo, palms etc. Typically it is not possible to see any growth rings in this set of trees.
- Exogenous: are trees with outward growth (such as additions of annual-seasonal rings), like Conifers (narrow leaves) (pine, fir), Deciduous trees (broad leaves) (teak, rose). These are used as engineering timbers.
Exogenous plants as the name suggests grow outward. The stems are formed by successive additional layer on outside. Timber is essentially derived by the new mass formed in the cambium between the wood and the bark every year. Trees of cold climates and substantial numbers trees of warmer climates are exogenous. Rings in the trunk or branch section, and pith with medullary rays extending outwards to the bark are two distinguishing features of exogenous trees. Exogens yield timber for furniture and construction. Exogenous trees are subdivided into two main classes: broad-leaved trees and needle-leaved trees, or conifers. Broad-leaved Woods generally contain no resins, and the density or weight is greater. They are usually hard, and due to their irregular structure, nett yield is lower.
The other botanical group of endogenous trees or endogens or grow inward from a hard exterior shell or, more commonly, end-wise by the acquisition of a new joint. Endogenous trees grow by forming new fibres within the trunk interspersed with the old fibres. Old endogenous stems have older and harder wood near the surface, whereas younger and softer centre. Timber from these trees has very limited engineering applications. Examples of endogenous trees are Palms, bamboos, canes, etc. These are not broadly useful for furniture or construction work, yet have their specific advantages and uses.
Commercial timbers of exogenous trees are classified as softwoods and hardwoods, though a very misleading nomenclature. Softwoods are timbers obtained from conifers, growing above certain altitude, and are supposed to be soft and lighter in colour. Hardwoods, are timbers that originate from the mainland and tropical areas are supposed to be hard and darker in colour. Many softwoods, though, are much harder and often of darker in shades than some of the hardwoods. Inversely many hardwoods are fairly soft and lighter in colour than some of the softwoods. Botanical names and commercial names of trees or timbers do not provide a true picture. There are multiple botanical names for the same specie adding to the confusion. Same timber is likely to be differently known commercially in various parts of the world.
Timber is a very precious commodity. It takes decades to grow a commercially viable timber tree. Deforestation has become a prime issue from ecological points of view. Several countries have banned or severely curtailed and controlled the export of timber. Similarly many countries have banned import of timber to limit deforestation world wide. Many governments and local authorities discourage timber structures and other uses of timber. Government of India has enforced conditions, so that usage of timber as doors and windows and other structural purposes are nearly banned, in government schemes. Similar conditions are likely to be followed by state governments also. So over the years use of timber is likely to be severely curtailed not only due to legislation but also its difficult availability and consequent upward pricing.
Timber grown in planned plantations is of consistent variety due to standard or a singular source of seedling or genetic derivation and grown in very controlled conditions. These results in trees with identical grain, colour and texture, belying the natural variations associated with woods.
Wood replacement products are of broadly two types. Wood-based composites such as plywood, block boards, chip and particle boards are likely to remain available, but only for a while. The availability of such products is also going to taper off in future. Wood ‘look-a-like’, make-believe, or pseudo wood products made of polymeric composites, painted, printed or layered materials are in the market.
Unlike a metal or plastic, wood is inherently a replenish-able resource, provided production and use are controlled and matched.