Timber Defects and Preservation
TIMBER DEFECTS AND PRESERVATION
Defect occurring in timber are grouped into the following five categories :
Defects due to conversion.
Defects due to fungi.
Detects due to insects.
Defects due to natural forces.
Defects due to seasoning.
1. Defects due to Conversion :
a. Chip Mark : Marks or signs placed by chips on the finished surface of timber.
b. Diagonal Grain : Formed due to improper sawing.
c. Torn Grain : Small depression formed due to falling of a tree.
d. Wane : Pressure of original rounded surface on manufactured piece of Lumber.
2. Defects due to Fungi :
Fungi attacks the timber when moisture content is greater than 20% or there is presence of air and warmth in timber. Some of the important defects due to fungi are
a. Dry Rot : Certain types of fungi attack on wood and convert it into dry form.
b) Wet Rot : Certain types of fungi cause chemical decomposition of wood and convert timber into grayish brown powder.
3. Defects due to Insects :The insects responsible for decay of timber are beetles, marine bores, termites.
4. Defects due to Natural Forces:
Important among these are Shakes : These are cracks which partly or completely separate the fibers of wood.
Types of Shakes :
a. Cup Shakes :
Rupture of tissues occur in circular direction.
Separate one annual ring from the other.
Occur due to non-uniform growth or due to excessive bending during a cyclonic weather.
b. Heart Shakes :
heart shakes timber defect
Cracks which extend from pith to sap wood in the direction of medullary rays.
Occur due to shrinkage of interior part of tree.
c. Ring Shakes :
Defect occurring in timber are grouped into the following five categories :
Defects due to conversion.
Defects due to fungi.
Detects due to insects.
Defects due to natural forces.
Defects due to seasoning.
1. Defects due to Conversion :
a. Chip Mark : Marks or signs placed by chips on the finished surface of timber.
b. Diagonal Grain : Formed due to improper sawing.
c. Torn Grain : Small depression formed due to falling of a tree.
d. Wane : Pressure of original rounded surface on manufactured piece of Lumber.
2. Defects due to Fungi :
Fungi attacks the timber when moisture content is greater than 20% or there is presence of air and warmth in timber. Some of the important defects due to fungi are
a. Dry Rot : Certain types of fungi attack on wood and convert it into dry form.
b) Wet Rot : Certain types of fungi cause chemical decomposition of wood and convert timber into grayish brown powder.
3. Defects due to Insects :The insects responsible for decay of timber are beetles, marine bores, termites.
4. Defects due to Natural Forces:
Important among these are Shakes : These are cracks which partly or completely separate the fibers of wood.
Types of Shakes :
a. Cup Shakes :
Rupture of tissues occur in circular direction.
Separate one annual ring from the other.
Occur due to non-uniform growth or due to excessive bending during a cyclonic weather.
b. Heart Shakes :
heart shakes timber defect
Cracks which extend from pith to sap wood in the direction of medullary rays.
Occur due to shrinkage of interior part of tree.
c. Ring Shakes :
