DEFINITION
Wood
preservation is the process of adding chemical to wood so as to prevent termites,
insects, weevils and fungi from attacking the wood. These chemicals are called
preservatives. It can be applied to wood through spraying or brushing.
Examples
of wood preservatives are creosote, coal- tar, solignum, chlorinatephenol, paints, etc.
Defects in Wood
Defects
are faults or irregularities in wood caused either naturally or during
processing of the wood which reduces the value or quality of the timber.
(1). Natural defects: These are defects which occur during the growth of a tree.
They include the following:
(a).Knots: A knot is a defect that occurs at the branch of a tree. If a branch falls from a tree it may leave a knot hole on the tree eg
(b).Cross grain: This is the condition which occurs when the wood fibre is not aligned parallel t o the axis of the piece of wood. it is caused by the manner the tree grew. It gives plants low strength.
(1). Natural defects: These are defects which occur during the growth of a tree.
They include the following:
(a).Knots: A knot is a defect that occurs at the branch of a tree. If a branch falls from a tree it may leave a knot hole on the tree eg
(b).Cross grain: This is the condition which occurs when the wood fibre is not aligned parallel t o the axis of the piece of wood. it is caused by the manner the tree grew. It gives plants low strength.
(c).Shakes: This is the complete
separation of parts of a stem in a living tree. it occurs because of stress
variation in the stem. There is the ring shake and the heart shake. Eg
(2)
Artificial defects: This is also
referred to as processing defects. It includes checks and warps.
(a)
Checks: This is a defect which
creates a separation of wood grain along the grain board. Eg
(b)
Warps: Twists in timber are called
warps. They may be caused by improper
seasoning procedure.
Examples on Images:
Class Work
What
is wood preservation?
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