2. LESSON OBJECTIVES
• To define wood and timber.
• To types of trees and timber (Softwood and Hardwood).
• To explain the physical characteristics of softwood and hardwood.
• To list the properties of wood.
• To explain and define the term “seasoning of timber”
• To state advantages of seasoning of timber.
• To explain the methods and types of seasoning timber.
3. DEFINITIONS
• WOOD-Is the organic matter obtained from trees
• TIMBER-Timber denotes wood which is suitable for building or carpentry
and for various engineering and other purposes.
4. TYPE OF TREES
Trees are classified into two groups
1. Endogenous trees
The trees which grow inwards in longitudinal fibrous mass
2. Exogenous trees
The trees which grow in out wards across horizontal
section of stem. These
trees are only fit for engineering construction.
5. Exogenous trees
fit for engineering construction( two types)
Conifers or Evergreen
They give soft wood and they have pointed leaves.
Examples: Déodar, Pine, Chir, Kail,etc
Deciduous or Broad leaf Trees
These have hard wood and they have broad leaves.
Examples: Teak, Sal, Shisham, etc
6. CHARACTERISTICS
NO: Item Soft woods Hard woods
1 Annual Distinct Indistinct
2 Colour Light Dark
3 Density Low High
4 Fire resistance Poor More
5 Weight Light Heavy
6 Strength strong for direct
pull & weak for
equal resisting
thrust
strong for resisting
tension,
compression &
shear
7. SESSONING OF TIMBER
As fresh timber which is obtained from trees contains about 30 to 40
% sap or moisture. This moisture is very harmful for the life of a
timber. Therefore, it is necessary to remove that moisture by applying
some special methods.
All those methods which are used for removing the moisture from
timber are collectively termed as seasoning of timber.
8. ADVANTAGES OF SEASONED TIMBER
1. It has reduced weight.
2. It is strong and durable.
3. It has resistance to decay or rot.
4. It takes high polish.
5. It is easier to work.
6. Its life is more.
9. TYPES OF TIMBER SEASONING
1. Natural Seasoning
2. Artificial Seasoning
a. Kiln Seasoning-special heating( 3 TO 12 DAYS)
b. Chemical Seasoning-carbon dioxide, ammonium carbonate or urea( 30 TO 40 DAYS)
c. Electric Seasoning-electric current is passed through the timber logs( 5 TO 8
HOURS)
3. Water Seasoning
10. METHODS
1. Natural Seasoning-timber is dried by direct action of air, wind and
sun. months or a year.
2. Water Seasoning-timber logs are kept immersed whole in the
flowing water to wash away the sap present in timber, then taken
out of water and exposed to air. 2 to 4 weeks.
