learn the seasoning and production and variety of uses of timber

5. 1. Pith: It is the inner most part of the tree and therefore the oldest
part of exogeneous tree when the plant becomes old, the pith dies
and becomes and dark and fibrous. It varies in shape and size
2. Heart Wood: It is the portion surrounding pith. It is strong and dark
in color. This portion is useful for several engineering purpose. It is
the dead part of wood. It consists of various annular rings.
3. Sap Wood: It is the layer next to heart wood. It denotes contains
sap and recent growth. It takes active part in the growth of trees by
permitting sap to move in upward direction. Annual rings of sap
wood are less sharply divided and are light in color. The sap wood is
also called as alburnum.
4. Cambium Layer: It is a thin layer of fresh sap lying among sap
wood and the inner bark. It has sap which is not still converted into
sap wood. If the bark is removed & cambium layer is exposed to
atmosphere then cells cease to be active and tree dies.
5. Inner Bark: It is a inner skin of tree defensive the cambium layer. It
provides protection to cambium layer.
6. Outer Bark: It is the outer skin of the tree and contain of wood
fibres. Sometimes it contains cracks and fissures
7. 7. Medullary Rags: These are thin radial fibers extending from
pith to cambium layer. They together hold annular rings. In some of
trees they are broken and some other they cannot be prominent

8. SEASONING
1.ARTIFICIAL
SEASONING
2.NATURAL
SEASONIG

14. (a) Boiling: In this technique timber is immersed in water and then water
is boiled for 3 to 4 hours. Then slowly it is dried. Instead of boiling
water hot steam can be circulated on timber. The procedure of
seasoning is fast, but costly.
(c) Chemical Seasoning: In this technique, in a solution of suitable salt
the timber is immersed .Then in a kiln the timber is dried. By chemical
seasoning ensures uniform seasoning of outer and inner parts of
timber.
(d) Electrical Seasoning: In this technique through timber high frequency
alternate electric current is passed Resistance to electric current is low.
In timber is high when moisture content. The resistance reduces as
moisture content reduces. Measure of resistance may be used to stop
seasoning at appropriate level.

15. Various defects which
are likely to occur in
timber may be grouped
into the following three
classes
(i) Due to natural forces
(ii) Due to defective
seasoning and
conversions
(iii) Due to attack by fungi
and insects

16. (i) Defects due to Natural
Forces: The following
defects are caused by
natural forces:
(a) Knots (b) Shakes
(c) Wind cracks (d) Upsets
a) Knots
c)Winds
CRACKS
and upset
b)SHAKES

21. If seasoning is not uniform, the
converted timber may warp and
twist in various directions.
Sometimes honey combining and
even cracks appear. This type of
defects are more susceptible in
case of kiln seasoning.