Defects Of Timber
1. Defects of Timber
A defect is an irregularity or abnormality occurring in or on wood which is responsible for its Strength reduction; Lowering of durability; Lowering of utility; Poor appearance; and, Decay
Classification of Defects:
a. Caused due to natural forces
b. Caused due to insects
c. Caused due to fungi
d. Caused due to conversion
e. Caused due to seasoning
a) Defects due to natural forces:
Chemical stain - the wood is sometimes discolored by the chemical action caused with it by some external agency. This is known as chemical stain.
Knots - these are the bases of branches or limbs which are broken or cut off from the tree. The portion from which the branch is removed receives nourishment from the stem for a pretty long time and it ultimately results in formation of dark hard rings which are known as knots. As continuity of wood fibers are broken by knots, they form a source of weakness
Shakes - these are longitudinal separations in wood between the annual rings. These are cracks which partly or completely separate fibers of wood. The separations make the wood undesirable when appearance is important
Twisted fibers - these are known as wandering hearts and caused by twisting of young trees by fast blowing wind. The timbers with twisted fibers is unsuitable for sawing
Ring galls - the rind means bark and gall indicates abnormal growth. Hence peculiar curved swellings found on the body of tree are known as rind gall. They develop at points from where branches are improperly cut off or removed. They are rarely found in a tree and the timber in this part is very weak and not durable.
Upsets - these indicate wood fibers which are injured by crushing or compression. The upsets are mainly due to improper felling of tree and exposure of tree in its young age to fast blowing wind
Burls - they are particularly formed when a tree receives shock or injury in its young age. Due to its injury, the growth of tree is completely upset and irregular projections appear
A defect is an irregularity or abnormality occurring in or on wood which is responsible for its Strength reduction; Lowering of durability; Lowering of utility; Poor appearance; and, Decay
Classification of Defects:
a. Caused due to natural forces
b. Caused due to insects
c. Caused due to fungi
d. Caused due to conversion
e. Caused due to seasoning
a) Defects due to natural forces:
Chemical stain - the wood is sometimes discolored by the chemical action caused with it by some external agency. This is known as chemical stain.
Knots - these are the bases of branches or limbs which are broken or cut off from the tree. The portion from which the branch is removed receives nourishment from the stem for a pretty long time and it ultimately results in formation of dark hard rings which are known as knots. As continuity of wood fibers are broken by knots, they form a source of weakness
Shakes - these are longitudinal separations in wood between the annual rings. These are cracks which partly or completely separate fibers of wood. The separations make the wood undesirable when appearance is important
Twisted fibers - these are known as wandering hearts and caused by twisting of young trees by fast blowing wind. The timbers with twisted fibers is unsuitable for sawing
Ring galls - the rind means bark and gall indicates abnormal growth. Hence peculiar curved swellings found on the body of tree are known as rind gall. They develop at points from where branches are improperly cut off or removed. They are rarely found in a tree and the timber in this part is very weak and not durable.
Upsets - these indicate wood fibers which are injured by crushing or compression. The upsets are mainly due to improper felling of tree and exposure of tree in its young age to fast blowing wind
Burls - they are particularly formed when a tree receives shock or injury in its young age. Due to its injury, the growth of tree is completely upset and irregular projections appear