Introduction

The progress of mankind from the earliest days of the eolithic age to
the present days of nuclear age can be closely associated with a great
deal of dependence on wood. The primitive man who lived in dense
forests used wood for shelter, fuel, weapons and tools. In due course of time,
wood came to be used as a major structural material for the construction
of boats, vehicles and bridges.

Later when ores of metals were discovered, wood was still needed as a fuel
for smelting the ores and for working metals. The phenomenal advances
made by man in the field of science and technology have made available
to him numerous materials for a multitude of diverse and sophisticated
requirements. Among them wood still retains a prominent place not only
in its natural form, but also in a variety of scientifically modified forms.
Wood and wood based products including paper, films and other wood pulp
products constitute the mainstay of our civilised life.
Wood being a renewable resource, it does make sense not only in continuing
but also in increasing our dependence on wood in preference to other
non-renewable resources

Wood, however,has certain limitations imposed by its composition
and structure.
It is made up of fibres oriented in one direction and, therefore, has most of its
strength and stiffness distributed in that direction.
As a result wood tends to crack and split easily along the direction of the
fibres.
Secondly, wood is made up of hygroscopic substance and therefore tends to
absorb and give up moisture from and into the surrounding air
simultaneously undergoing dimensional changes.

On account of the anisotropic nature of wood such moisture induced
dimensional changes are non-uniform, leading to warping and cracking.