Hard and Soft Wood
Hard and Soft Wood: Wood obtained from tree is the chief product of forest. It has been universally acceptable as raw material for manufacturing wooden products or appliances. From the pre-historic times, wood has been utilized an important source of getting heat by firing it. It has been utilized as an mazor construction material for making shelter for the basic need of human being. As the civilization advanced, it gained tremendous importance as special material for boatbuilding, for piling to support docks and railroad tracks. But in modern times, with the advance of wood chemistry, the uses of wood have recognized its importance in manufacturing cheap useful products used in day today life such as paper, furniture, textiles, plastics and hundreds of chemicals and extractives. The wooden products as plywood have superseded in some products in comparison metallic and ceramic materials. Compressed wood has also replaced some metals for gears and die casts. In war-time, in Europe, wood has been used as a source of wood gas for propelling automobiles. Similarly clothing has-been made from wood cotton and wood wool. The useful work on wood is being generally carried out in a most common shop known as carpentry shop. The work performed in carpentry shops comprises of cutting, shaping and fastening wood and other materials together to produce the products of woods. Therefore, carpentry shop deals with the timber, various types of tools and the art of joinery. In wood, there are two types of cells namely radiating outward from the center of wood cross-section and running parallel to the length of wood. Trees are generally classified into exogenous and endogenous types according to manner of growth. Exogenous types are also known as outward growing trees which produce timber for commercial use. They grow outward and the additional growth which occurs each year takes place on the outside of the trunk just underneath its bark, while the innermost timber continues to mature. Each time the growth cycle is completed the tree gains one more growth ring or annual ring. In counting these rings, the age of a tree can be determined, as each ring represents one year of growth.
Endogenous trees are also known as inward growing. They grow inwards i.e., every fresh layer of sapwood is added inside instead of outside. Cane, bamboo and coconut are examples of such endogenous trees. Timber is a common name imparted to wood suitable for engineering, construction and building purposes. Timber is obtained from trees by cutting the main body of tree in the suitable sizes after the full growth of tree. The timber structure is consisting of annual rings, heartwood, sapwood, pith, cambium layer, bast, medullary rays and bark.
HARD AND SOFT WOOD: Hard wood is generally obtained from broad leaves or deciduous trees where as the softwood from trees having needle shaped yes or conifers. The major differences between hard wood and soft wood are given as under. Table 1 Difference between Hard Wood and Soft Wood
TYPES OF COMMON TIMBERS, THEIR QUALITIES AND USES: The common types of well recognized timbers available in India are Shisham, Sal, Teak,
Deodar, Mango, Mahogany, Kail, Chid, Babul, Fir wood, Walnut and Haldu,. Out of these, Deodar, Chid, Kail, Fir wood and Haldu fall in the categories of softwoods and Shisham, Sal, Teak, Kiker, Mango, Walnut fall in the categories of hardwoods. Some of the other foreign timbers commonly used in India are Ash, Burma, Hickory, Oak and Pine.
- Shisham is dark brown in color and it possesses golden and dark brow stripes. It is very hard to work and generally wears or blunts the sharp edge of cutting tool very soon. It is available in India in Himalayan range at heights from 1000-1500 meters and in deep forests. It is recognized as highly strong and durable wood and it is mainly used for making good variety of furniture, tool handles, beds, cabinets, bridge piles, plywood etc.
- Sal exists in rose brown color which slowly turns into dark brown. This wood is commonly available in India in Himalayas, M.P and U.P. It is free from attack of white ants insects and it is very difficult to work. It has poor finish and therefore is not used for decorative furniture. It finds tremendous applications in making doors, windows, cots, wooden handles, furniture and railway sleepers etc.
- Teak wood is hard, very costly and it possesses wide applications. It is available in golden yellow or dark brown color. Special stripes on it add to its beauty. In India, it is found in M.P. It is very strong, durable and it maintains good polish. It is mainly used for making good quality furniture, plywood, ships etc.
- Deodar is white in color when soft. But when it is hard, its color turns toward light yellow. It is strong and durable. It provides fragrance when smelled. It is not easily attacked by insects as it has some quantity of oil in it. It is commonly available in Himalayas at a height from 1500 to 3000 meters. It is used for manufacturing of doors, furniture, patterns, railway sleepers etc.
- Mango is brown in color and it can be easily shaped in various products. It is widely used in India as a cheap wood for making doors, packing cases, toys and inferior furniture.
- Mahogany is reddish brown in color which is highly durable when dry. It also contains some oil in it that prevents it from the attack of insects. It is commonly utilized for manufacturing cabinet, fine furniture, pattern making work etc.
- Kail wood possesses too many knots in it. This wood is commonly found in Himalayas of India. It yields a close grained, moderately hard and durable wood which can be easily painted. It is commonly utilized for making cheap furniture, wooden doors, packing case etc.
- Chid is also known as Chir. Its color is dark brown when is soft, but it is reddish brown when hard. It has stripes of dark brown color. It has oily smell and is used for interior work in the house.
- Babul is close grained tough and pale red colored wood and is used for making tool handles etc.
- Fir wood is light brown in color when soft but harder variety is found in dark brown color. It can be easily attacked by insects. It is commonly utilized for making drawers, packing cases, doors etc.
- Walnut is a good variety of wood which resists the attack of white ants. It can be polished easily in a better way. This wood is generally used for making musical instruments, furniture, cabinet work, decoration work etc.
- Haldu is white in color at the time of cutting, but once cut, its color becomes yellow. It can be dried and polished satisfactorily. It is widely used for making small objects such as stool, picture frames, trays, cabinet etc.