Question

1. Describe what a) Softwoods are, b) hardwood are, c) Which types of tress are used the most for manufacturing structural lumber.
   Describe that the following terms mean:

a) Moisture Content

b) Fiber Saturation Point

c) Equilibrium Moisture Continent

d) Dry Lumber 


e) Green lumber

Answer 1

a) Softwoods are the type of wood that is derived from the conifers tree which is also known as evergreen tree and leaves of these trees does not fall till the new ones are grown. They are given the name conifers because tree bears cone-shaped fruits. Examples of softwood are pine, redwood, deodar, etc. Softwood is used for- paper, windows, door, etc

b) Hardwoods are the type of woods that is derived from the deciduous tree which is also known as broadleaf tree and leaves of these trees fall in autumn and new ones appear in the spring season. Examples of hardwood are teak, shisham, sal, walnut, etc. It is used for a high quality of furniture, flooring, etc.

c) As both hardwoods, as well as softwoods, are the parts of the exogenous trees. Mostly, for manufacturing structural lumber deciduous trees are used as they yield hardwoods which are relatively stronger in all directions for resisting.

COMPARISON  OF HARDWOOD AND SOFTWOOD

	Softwoods	Hardwoods
Annual rings	Distinct	Indistinct
Weight	Light	Heavy
Strength	Strong for direct pull &weak for resisting thrust of shear.	Equally strong for resisting tension, compression, and shear
Fire resistant	Poor	More
Color	light	dark
Medullary rays	indistinct	distinct
Structure	resinous and split easily	non-resinous and close-grained

a) Moisture content can be defined as the amount of water or moisture in the wood. It the ratio of the mass of water in the wood to the mass of the wood without the water. And for removing the moisture from the wood various kind of seasoning is done. The moisture content in a well-seasoned wood is 10-12% by weight, depending on the relativity humidity of the air.

b) Fibre Saturation point of wood can be defined as the moisture content in percentage when the cell walls are saturated with water and the cell cavity contain no water and this is during the drying process of wood.

c) The equilibrium moisture content of wood is the state corresponding to the relative humidity and temperature of surroundings when the moisture content of wood remains constant i.e. neither gaining moisture nor losing moisture and it is important to attain during the process of drying of wood.

d) Dry lumber is when the moisture content of wood is reduced it is known as dry lumber. This is done by various processes like natural seasoning, kiln seasoning, chemical seasoning, etc. This is done to import hardness, stiffness, strength, to reduce the tendency of lumber to crack, shrink and wrap.

e) Green lumber can be defined as when the wood is not properly seasoned means the amount of moisture is present in the wood and it is used in such a way without reducing the moisture content. So, green lumber is wood which contains moisture in it and the percentage varies from 19% to 100%. And if the wood is used as fuel it will produce less heat as compared to dry lumber.