The Timber Project is a non-profit organisation devoted to building structures that improve the quality of life for refugees stranded in Greece and along the Balkan route

2. PROJECT REPORT OF TRAINING
WORKING OF TIMBER
HEAD OF DEPARTMENT (CIVIL)
NAME MISS AMBALA
SUBMITTED TO
NAME MISS AMBALA
SUBMITTED BY
SUDHIR PASWAN
ROLL NO - 140680107030

3. Objective: To learn about processes used in wastewater
treatment plant
1. Discuss about the different types of timbers.
2. Discuss the application and use of timbers
in construction.
3. WOOD WORKING TOOL
4. Understand the properties of timber.
5. Discuss about the defects in timber.
6. Discuss about different types of preservatives
treatments.

4. Discuss about the different types of timbers.
1 Classification of Trees
All commercial timbers can be classified into 2 broad groups: softwoods and hardwoods.
SOFTWOOD
 Softwood is produced from the
gymnosperms, the coniferous
trees such as pines and spruces,
which have characteristic needle-
like leaves. These trees are
generally evergreen. Traditionally
softwoods have been used
primarily for structural ti b m ers
and are grad de specifi ll ca y for
this purpose
HARDWOOD
 Hardwood is produced from one
group of the angiosperms, known
as dicotyledons, which are the
broad leafed trees, such as oak,
beech and ash. The temperature
zone hardwoods generally
season-based, while most tropical
hardwoods retain their leaves all
year round. The major use of
hardwoods is in furniture and
cabinet manufacture

7. DIFFRENCE BETWEEN HARDWOOD
AND SOFTWOOD
HARDWOOD SOFTWOOD
 ƒSoftwoods come from coniferous trees
 ƒSoftwood trees have a much simpler
cell structure then hardwoods
consisting of mainly large
longitudinal cells consisting of mainly
large longitudinal cells –
uninteresting patterns of
uninteresting patterns of grain
 Hardwoods come from broad-leafed trees.
leafed trees.
 Hardwoods have complex cell structures
Hardwoods have complex cell structures –
and beautiful grain and beautiful grain
patterns.

8. Discuss the application and use
of timbers in construction.

13. Use # 1. Fuel:• Timber has a wide variety of uses in construction and as an industrial raw material, but the most important single use for
timber is as fuel. About 40 per cent of the total timber removed from forests all over the world is used in this way.However,
the proportion of timber production used as fuel differs very much in different parts of the world, depending on the
availability of other fuels such as coal, the degree of control exercised over the forests by governments and the fuel
requirements of the various countries.
• Those countries in which forest industries are most highly developed generally use least timber for fuel, while in those areas
where forestry is little- developed, fuel is the major use, consuming almost the entire output. The African and South
American continents consume a very large proportion of their timber as fuel, both for domestic and industrial purposes, and
in fact most tropical countries have a high consumption.
• A notable exception to this pattern is Malaysia, where, though timber is a major product of the country, the proportion used
for fuel is very small. This is partly because a rather higher standard of living than in many developing countries enables
many people to use kerosene, gas or electricity rather than wood as the major domestic fuel, but also reflects the use of
wood from rubber plantations rather than from the forests, as an industrial and a domestic fuel.
• Petroleum supplies most industries with their power and is readily available. This contrasts with the position in many Latin
American countries, where, because little coal or oil were available, wood has traditionally been used to power industries
and locomotives. As oil reserves are increasingly exploited less wood may be required for fuel.
• The European countries, North America and Japan use relatively little wood for fuel, though the pattern is not uniform.
Those countries which are short of timber, such as Britain, but have ample supplies of coal and gas, use very little timber for
fuel.
• Others, such as Finland, where timber is cheaply and readily available and coal is difficult to obtain, use a larger proportion
(about one-fifth) of their timber for fuel. In Japan, too, despite the rigorous forestry practices, the shortage of domestic coal
and oil supplies means that about one-sixth of the total timber output is used as fuel.
• In southern Europe, in such countries as Spain, Yugoslavia and Turkey, where industrial development is slower and the
standard of living lower than in much of Europe, the proportion of timber output used as fuel is very high. The low
consumption of timber as fuel in North America reflects both the availability of a wide range of other fuels and the high
standard of living. Canada uses less than 5 per cent of its timber for fuel.

14. Use # 2. Construction
• After fuel the most important use for timber is in the building and
constructional industries. It has traditionally been used to build houses or
parts of houses, and despite the use of steel and concrete for a wide range
of building purposes nowadays, it continues to be used in this way.
• Although the development of newer materials has reduced the proportion
of total timber supplies used for construction, the continual growth of
population in the world, and hence of the construction industry, has
increased the amount of timber used for this purpose.
• Apart from house-building, timber is also required for shipbuilding in
many areas, though its greatest use for ships was in the past, when not
only timber but pitch, resin and turpentine were consumed in large
quantities in the traditional shipbuilding areas of northern Europe and
eastern North America. Timber is also the basis of a wide range of
woodworking industries producing furniture, boxes, crates and matches.
• While most of the timber used for fuel is hardwood from tropical forests
the situation in the industrial use of timber is the reverse. Most timber
used for construction, pitprops, matches and so on is softwood.

15. Timber is used in the construction
industry in three main ways:
(a) Sawnwood:
Whole timber is used for heavy- duty construction work such as
railway sleepers or the construction of piers and jetties and for
such purposes hardwoods such as the resistant jarrah and karri
hardwoods of Australia are ideal. Pit-props, however, are usually of
coniferous logs. In tropical countries the strong, damp-resistant
timbers from the mangrove swamps are used for such
construction.
Sawnwood, mostly from coniferous trees, is also used in the form
of planks, boards, beams and so forth in house building. Tropical
and temperate hardwoods are used for boats. Cabinet woods such
as mahagony, rosewood, ebony may be used for furniture, while
cheaper furniture is made from softwoods, e.g. pine.

16. (B) Plywoods and veneers
:
Besides its use in the form of planks, wood may
be cut into thin sheets which are subsequently
glued together to form a light but strong material
called plywood, which is much used for internal
construction such as doors, built-in furniture and
so on. Thin sheets of valuable woods such as
ebony, mahagony, oak, walnut, may be fixed to
less valuable woods to make a veneer for
furniture- making.

17. (c) Fibreboards:
In addition to sawn timber and processed woods
such as plywoods, timber is also used in the
form of fibre- and particle- boards. These are
made from pulp or from sawdust and other
waste materials and are thus by-products of the
saw-milling and pulping industries. These types
of board, such as hardboard, blockboard,
chipboard, etc. are used for furniture and
internal construction work such as linings,
ceilings and so on.

18. Use # 3. Pulp and Paper:
In terms of value the most important use of timber is in the pulp and paper industry. This
industry is constantly expanding and it creates an ever-increasing demand for timber.
Wood contains two substances, lignin and cellulose, and the object of pulping is to extract
the cellulose from which paper (and synthetic textiles) are made. Both hardwoods and
softwoods can be used for pulping, but the greater ease of dealing with softwoods and
the predominance of softwoods in the main world industrial areas has led to the
dominance of softwoods in this industry.
Wood is not the only substance from which paper can be made and a wide variety of
vegetable fibres have been used in different parts of the world for many hundreds of
years. The art of paper-making first originated in China. Many simple paper-making
processes are still carried out on a small scale but are of little international importance.
More important is the attempt to use fibres other than softwood cellulose in order to
conserve forest resources.
The fibres which could be used in this way are by-products of other industries and, as
such, would represent a major economy for many countries if efficient processes for
converting them into paper could be evolved. Banana trees, sugar bagasse (cane from
which the sugar has been extracted), padi straw and old rubber trees are sources of pulp
which are being experimented with, but as yet they have not been used on a large scale.
Temperate hardwoods, however, are being increasingly used for pulp production. Rags
and wastepaper can also be converted into pulp for re-use as newsprint, though high
quality paper cannot be made, and this practice is becoming more and more important in
the major paper-consuming countries such as the U.S.A. and Britain. At present, however,
90 per cent of pulp is derived from wood.

19. There are three processes by which wood is converted into pulp and the method used
depends on the type of wood and the type of paper to be produced
(a) Mechanical process:
About one-fifth of the world production of woodpulp is produced by the
mechanical process, in which the wood is ground up by revolving
grindstones and then soaked in water to produce a fibrous mass. This is a
simple and fairly cheap process but has some disadvantages. It can only be
used to deal with softwood timber containing little resin and having long
fibres. This means that it is restricted mainly to spruces and that pines and
hardwoods cannot be used.
The method produces little waste material but the end-product is not
suitable for all types of paper and only newsprint and low-grade papers
can be made. The process is most important in Canada, where suitable
trees are available and as a result Canada is the largest producer of
newsprint in the world, making about 36 per cent of the total.
The process is carried out in large plants which require an enormous
capital outlay and is most economical where a constant, large production
can be maintained. It is thus least important where supplies of spruce are
small, or where pulp production is only on a small scale.

20. (b) Chemical process
:
The chemical and semi- chemical processes together account for about 80 per cent of pulp
production. This is because they are more versatile and can use a wider range of raw materials.
However, the chemical process is more expensive and more wasteful than the mechanical process.
Running costs are high, outlay on chemicals is great, and less of the initial log is utilized in the final
pulp. However, the pulp produced is of better quality and is used for high-quality papers.
In the chemical process the timber is soaked in acids or alkalis in order to dissolve the lignin, leaving
the pure cellulose. Different chemicals are used for different purposes. The sulphite process, in
which calcium bisulphite is used at high temperature and pressure, produces pulp for book papers
and high- quality papers, but requires less resinous woods.
The sulphate process, using sodium sulphate and caustic soda, produces somewhat coarser papers
for wrapping and packaging, but can use resinous woods such as pines. For this reason it is
particularly important in the U.S.A. where much of the timber production is of very resinous pines
from the southern states.
The greater importance of the packaging industry in the U.S.A. is another reason for this
concentration. The better quality timbers, and the need for a larger proportion of high quality paper,
make the sulphite process more important in Europe.
Chemical processes are less demanding of electricity and water supplies than are mechanical
processes but the chemicals needed may amount to half the weight of the logs used. However, the
sulphate process has the advantage that chemicals can be recovered to some extent and re-used,
reducing costs and also reducing river pollution by factory effluents.

21. (c) Semi-chemical process:
The semi-chemical process is in two stages. Chips of wood are first treated with chemicals to remove
some of the lignin and afterwards the wood is broken down mechanically to extract the cellulose.
This process is most suited to the pulping of hardwoods and thus, although it is relatively little used
at present, its use may expand as the pressure on softwoods increases and more hardwoods have to
be used in the pulp and paper industry.
The U.S.A. derives about 10% of its pulp by the semi- chemical process, and is the largest producer
of semi- chemical pulp. Pulp made by the semi-chemical process is chiefly used to make heavy-duty
cardboard and fibreboard rather than paper.
The pulp produced by the above processes has to be processed in various ways in order to produce
the wide range of papers and cardboards which are in everyday use. The main stages in paper
manufacture are the further refining and bleaching of the pulp, which is then beaten and rolled out.
Better quality papers are dyed, sized and coated with a chalky solution to give them more body and
a smooth, shiny surface.
Paper is not the only product of the pulp industry. Of growing importance is the manufacture of a
wide variety of fibreboards and particle boards for constructional purpose. These are made from
pulp, saw- mill waste, such as sawdust, or forest waste, such as chips and offcuts. These board
products have only become important in the twentieth century and particle board was first made in
Germany during the Second World War, as a way of saving timber.
Fibreboard is made mostly from mechanically or semi-chemically processed pulp and both
softwoods and hardwoods can thus be used. Sawmill residues are also used to a large extent,
especially in Europe. The leading producers are the U.S.S.R., the U.S.A. and Sweden. Particle board
can be made from a wide range of materials, not necessarily pulp, and consists of a mass of small
particles of lignocellulose bonded by resinous material to form a board. Much forest waste is utilized
in its production.
Particle board mills are small and cheaper to set up than fibreboard mills but the cost of resins for
bonding the particles is often greater than that of the wood. Both fibreboard and particle board
production are increasing and should be encouraged because they can make use of hitherto wasted
timber materials and at the same time can ease the demand for sawn-timber in the construction
industry.

22. Use # 4. Synthetic Textiles:
Wood cellulose is the basis of the synthetic textiles known as rayon. The
chief source of cellulose for the textile industry is spruce wood pulp but
cellulose is also extracted from cotton linters (the burrs which remain
attached to the cotton seeds after ginning). The cellulose is dissolved in
caustic soda and carbon bisulphide and the resultant solution is extruded
through a spinneret with numerous holes into a coagulant to make fila-
ments of viscose rayon.
Another process, using acetic acid, acetic anhydride and acetone produces
a solution which is extruded into a current of warm air rather than a
coagulant. The rayon so produced is called acetate. Both processes have
been used since the end of the nineteenth century but acetate has only
become important since 1930.
The rayon filaments may be used as they are to produce ‘artificial silk’ or
may be cut into staple lengths and then spun, woven, dyed and finished in
the same way as ordinary textiles. They may thus be given the properties
and appearance of the traditional textiles such as cotton or wool. The
U.S.A., Japan and European countries such as Italy are the major rayon
producers

23. Use # 5. Other Uses
Various types of timber have a wide range of uses
as dyestuffs, chemicals and so on but many of
these applications have been superseded by the
development of synthetic chemical dyes and
resins. Wood does still yield materials for the
disinfectant and paint-making industries. Trees
also yield tannin, gums, resins and drugs.

24. WOOD WORKING TOOL

25. Tack Hammer
One side of the head is magnetic and used for starting short tacks.
Straight Claw Hammer
The hammer head is the same as a curved claw hammer, but the claw is nearly straight.
Weight 16-28 oz. Head may be smooth or serrated. Also called a Ripping hammer.
Curved Claw Hammer
Used for driving and puling nails. Face is commonly rounded for finish work. Weight 13-16 oz.
Mallet
Heads are made of wood, plastic, rawhide and
rubber. Also called a Soft Headed Hammer.
Shingler’s Hatchet
It has a gauge that can be adjusted for the desired shingle exposure and has a nail
pulling slot in the back and above the cutting edge.

26. Back Saw
This saw should be used in a horizontal position.
Hand Cross Cut Saw
The standard length is 26 inches. Typically 8-12 teeth/inch.
Hand Rip Saw
The edges of the teeth are not beveled, but are shaped like chisels. Typically 4-7
teeth/inch.
Keyhole or Compass Saw
Used for sawing curves, especially where the cut must be started from a hole bored
with an auger bit.
Coping Saw
The blade is installed to cut on the pull stroke.
Belt Sander
Sands or cuts using a sanding belt. Used for course sanding of large surfaces.

27. Jack Plane
Planing should be done with the grain of the wood. Note tail behind the handle.
Circular Saw
Primarily used for cutting wood, however many blades types are available for cutting sheet metal,
metal, stone, and various other products. Available as a direct drive or worm drive.
Smooth Plane
Sizes range from 5 1/2 to 10 inches long and 1 1/4 to 2 3/8 inches wide.
Finishing Sander
Sands by a vibrating action.
Block Plane
Sizes range form 5 1/2 to 7 inches long and 1 3/8 to 1 5/8 inches wide. Used to plane
the end of a board.
Router
Depth of cut is adjustable. Used to shape wood (ex. round the edge of a board).

28. Circular Saw Blade
The size is determined by the diameter of the blade.
Jig Saw
Many variations of blades are available for cutting wood, plastics, and other soft materials. Also
called a Saber Saw
Power Miter Saw
The saw pivots on the miter box for various angles.
Nail Gun
Nails are fed automatically from a loading chamber and are
dispensed by pulling the trigger.
Planer
Used for planing wood surfaces. A portable power version of a hand plane.

29. Reciprocating Saw
Similar to the jig saw but much larger and used for heavy duty work.
Disc Sander
A stationary power tool with a 6-12 inch sanding disc.
Forstner Bit
A power bit for drilling flat bottomed holes in wood. Commonly found in sizes 3/8-2 inch.
Hole Saw
Hole saws come in sizes from ¾ to 2 1/2 inches and one mandrel fits all.
Auger Bit
The straight round shank adapted for power drills.

30. Spade Bit
A wood boring bit with a hex shaft to be used in a power hand drill or drill press.
Expansive Bit
The shank is a square taper, adapted for the bit brace.
Surform Tool
A tool like a wood rasp with a replaceable cutter. Available in flat, round, and half round
shapes.
Nail Set
The point has a slight hollow at the end.
Hand Screw Clamp
The wooden handles are mounted on opposite sides of the jaws.
Cat's Paw
A tool used to pull nails
Wood Chisel
It is sharpened only on one side to a 25 or 30 degree angle and may be used with or across
the grain.

31. Wood Rasp
Other rasps are 4-in-hand and horse rasps.
Utility Knife
A sharp knife for cutting drywall, roofing felt, etc.
Drywall Trowel
A flexible trowel for applying drywall compound and tapping.
Drywall Saw
A tapered hand saw for cutting drywall.
Drill Press
A stationary drill.

32. Band Saw
Used for making curved cuts in wood or metal.
Radial Arm Saw
A saw designed to cross cut and rip with the ability to cut compound
angles.
Table Saw
A stationary saw used primarily for ripping lumber and sheet materials.

33. Properties of Timber
The quality of timber must be ensured before using it for a purpose. The quality can
be ensured by investigating the properties of timber. Here we have discussed both
physical and mechanical properties of timber which affects timber quality.
Followings are the physical and mechanical properties of timber
1. Colour
2. Appearance
3. Hardness
4. Specific Gravity
5. Moisture Content
6. Grain
7. Shrinkage and Swelling
8. Strength
9. Density
10. Toughness
11. Elasticity
12. Warping
13. Durability
14. Defectless
15. Workability
16. Soundness
17. Free of abrasion

34. • Colour-Color is a uniform property by which most trees are characterized as they show variation from tree to tree. Light
color indicates weak timber. For example, freshly cut teak, Deodar, and Walnut have a golden yellow, whitish and dark brown
shades respectively.
• Appearance-Smell is a good property as timbers for few plants as they can be identified by their characteristic aroma.
Fresh cut timbers have a good smell. For example resinous smell from pine.
• Hardness-For the resistance of any kind of damage, hardness is an obvious property.
• Specific Gravity-Variation of timber in specific gravity (0.3-0.9) is found. It depends on pores present inside timber. The
specific gravity of this light material is less than that of water (<1). But in case of compact wood where pores are almost
absent and become heavier, their specific gravity increases up to 1.5.
• Moisture Content-Timbers are hygroscopic and gain water from nature (atmosphere). The absorption of water or
dehydration depends on atmospheric humidity. If timbers moisture content is high that means the timber quality is low.
Water content is the risk of fungal attack.
• Grain-Several types of grain arrangement found. On the grain structure quality of timber varies. Grains remain closely
related.
• Straight grain: Arrangement of vascular tissue (xylem and phloem) is important which grow parallel to the length of the
timber that is termed as straight grain.
• Coarse grain: vascular tissue and fibre arranged broadly and widely.
• Interlocked grain: Instead of parallel arrangement twisted, a spiral arrangement may be found.
• Shrinkage and Swelling-The percentage of shrinkage and swelling varies from plant to plant. Some give higher percentage
after drying. Shrinkage starts when cell walls of timber start to release water. In moisture atmosphere timber swells when
cell walls absorb water. Good quality timbers swell less. Timbers having thicker wall swell more than a thinner one.
• Strength-Best quality timbers have the highest strength. Strength means capable to bear loads. Anisotropic material like
timber has different structure at the different portion. So, the strength of timber is different at different points. Grain
structure determines the strength of the timber. Some types of strength are
• Compressive strength: 500 kg/cm2 to 700 kg/cm2 load is enough to test timbers strength.
• Tensile strength: When timber is enough strong to the tensile force. If perpendicular force is made then timber is weaker.
500-2000 kg/cm2 is the range of tensile strength load.
• Transverse strength: Enough bending strength indicates good quality timber.

35. • Density-Timber having higher density have a thicker wall. An important property
that quality of timber. Moisture content: Presence of defects: There may be some
of the natural and artificial defects in timber such as cross-grain, knots, and shakes,
etc. All of them cause a decrease in the strength of the timber.
• Toughness-Timber has to have the capability to bear shocks, jerk. Anti-bending and
ant splitting characteristic is needed. Old timbers have annual rings which indicate
their age is a good indicator.
• Elasticity-Another property elasticity means timber should attain its own shape
after use. Because of this quality, it is used in sports bat.
• Warping-Environmental change with season can’t effect good quality timber.
• Durability-A good quality timber has the property to resist the attack the infection
of fungus or other insects. This resistance quality makes timber better.
• Defectless-This property is gained if the timber is from a sound tree. A defectless
tree is free from sap, shakes, and dead knots. To know more about timber defects
read:
• Workability-A good timber is always easy to work on it. Easy to drag using saw on
good timber. The finishing can be done well.
• Soundness-A good quality timber gives good sound.
• Texture-The texture of good timber is fine and even.
• Free of Abrasion-Timber should not be damaged by the external environment. It
has to gain the ability to protect its skin.

36. Discuss about the defects in timber.
Timber is a natural product and every natural product has some
imperfections. Timbers are not excluded from that. Most of the defects in timber
cause weakness or others sorts of difficulties. However some defects can be
beneficial for a specific type of work, for example, twisted wood is good for
making a bowl out of timber.
The followings are the five main types of
defects in timber:
1. Defects due to Natural Forces
2. Defects due to Attack by Insects
3. Defects due to Fungi
4. Defects due to Defective Seasoning
5. Defects due to Defective Conversion

37. 1.Defects due to Natural Forces
• Knots: Knots are the most common defects caused due to natural forces. During the growth
of a tree, branches close to the ground or lower branches die. Bases of those branches
remain in the tree as the trees grow. These bases may create imperfection known as knots.
Types of Knots: Knots are of two types.
Dead knots: The remains of damaged branches after drying out they become loose and fall
out.
• Live knots: They are sound and firm. If small, are not great of a defect.
• Live knots are usually not a problem as they remain firmly attached to the timber. But in dead
knots, they are loosely attached and reduce strength. Knots decrease the strength of the
wood and thus lower its value for structural uses. Knots cause serious defects when the load
is perpendicular to the grains.

38. 1.Twist: Twist in timber rotates the ends of the timber in opposite directions. The main
reason behind this defect is twisting of the trees by the strong wind.
Twisting of the trees by the strong wind. Source:commons.wikimedia.org
2.Shakes: Shakes are timber defects that occur around the annual ring or growth ring
of a timber. In other words, cracks or splits in the woods are called shakes.
It may or may not be a structural problem depending upon depth and use. The main
problem is aesthetic. Where the appearance is important, shakes are undesirable.

39. 1.Types of shakes: Shakes can be classified into three main categories:-
1.Star Shakes: This type of shake starts propagating from the bark towards the sapwood and
sometimes even towards the heartwood along the lines of medullary rays. Cracks are wider on
the outer edge or bark and narrower on the inside (usually sapwood, sometimes heartwood).
The main reasons behind star shakes are extreme heat or frosting during the growth of the
trees and rapid or uneven seasoning after cutting off the timber. Extreme heat or frost causes
temperature difference, which causes shrinkage leading to the crack.
2.Cup and/or Ring Shakes: Cup shakes follow the annual growth ring. It is capable to
separate the growth ring partially or completely. When the crack separates the annual ring
completely, it is called ring shakes. So, all ring shakes are cup shakes, but all cup shakes are
not a ring shape. Excessive frost action is the main reason for this type of crack.
3.Heart Shakes: Unlike star shakes, heart shakes starts propagating from the pith to the
sapwood along the lines of medullary rays. Shrinkage of the interior part of the timber causes
this crack.
2.Rind Galls: THe meaning of rind is bark and gall is abnormal growth. So abnormal growth of the
bark of the trees is called rind galls. Improper cutting of branches causes this abnormal growth. Wood
from this portion of the timber lacks strength and desirable in structure.
3.Upsets: Upsets in various wood indicate that the tree was subjected to crushing or compression.
Improper felling of trees, heavy wind blowing during the young age of the tree these are the main
reasons behind this type of defect.

40. 2.Defects of Timber due to Attack by Insects
• Insects like beetles, termites or marine boars eat wood,
make holes and weaken the strength of the wood.
• Beetles are small insects that make holes in almost all
the sapwoods. The larvae make tunnels through the
sapwood in all directions and turn wood into powder.
• Termites live in a colony. They are very fast in eating
woods and making tunnels through it. Only a few good
kinds of wood can withstand the action of termites.
• Marine boars are found in salt water. Usually, they
make tunnels in wood to take refuge or shelter. All
kinds of wood or timber are vulnerable to this kind of
insect

41. 3.Defects in Timber due to Attack by Fungi
• Stain: When fungi feed only on sapwood, where
the food materials are stored, it causes a stain.
Heartwood doesn’t contain these kinds of food
materials and is not affected by it. Stain action
causes color but does not affect the strength of
the wood.
• Decay: wood eating or wood destroying fungus is
responsible for this type of defect in wood. This
type of fungi breaks down the cell structure. Both
sapwood and heartwood are affected by them.
Considerable strength reduction occurs.

42. 4.Defect in Timber due to Defective Seasoning
• Faulty method of seasoning causes serious defects in woods.
During seasoning of timber, exterior or surface layer of the timber dries
before the interior surface. So, stress is developed due to the difference in
shrinkage. In a perfect seasoning process, stress is kept minimum by
controlling the shrinkage. Some of the defects resulting from defective
seasoning are as follows:-
• Bow: Curvature formed in direction of the length of the timber is called
bow.
• Cup: Curvature formed in the transverse direction of the timber is called a
cup.
• Check: Check is a kind of crack that separates fibers, but it doesn’t extend
from one end to another.
• Split: Split is a special type of check that extends from one end to another.
• Honey Combing: Stress is developed in the heartwood during the drying
process or seasoning. For these stresses, cracks are created in the form of
honeycomb texture.

43. 5.Defects of Timber due to Defective Conversion
• Boxed Heart: This term is applied to the timber, which is
sawn in a way that the pith or the center heart falls entirely
within the surface throughout its length.
• Machine Burnt: Overheating is the main reason for this
defect.
• Machine Notches: defective holding and pulling causes this
defect.
• Miscut: erroneous cutting or sawing of wood causes this
defect. Lack of experience in sawing and carelessness is the
main reason for erroneous cutting.
• Imperfect Grain: Mismatch in grain alignment.
•

44. • Reduction of moisture content along with improving some qualities before
the use of woods is called seasoning of timber. By seasoning, generally,
the moisture is reduced to about 15% where new cut woods bear about
50%
Reasons for Seasoning
Seasoning of timber is done to fulfill some specific
requirement. Followings are the reasons to perform
timber seasoning.
1. To change and improve the properties of wood.
2. To make a correct percentage of shrinking of woods.
3. To make a confident use of woods.
4. To reduce the adverse behavior of woods.

46. Natural Seasoning
• Seasoning of woods or timbers using natural elements is called natural seasoning. eg. water
and air seasoning.
• a. Water seasoning-Removal of wood sap immersing logs into water flow is called water
seasoning. It is carried out on the banks of the river while thicker ends are kept towards
upstream. After that, the logs are allowed to dry. Disadvantage: It is time consuming such as
2 to 4 weeks generally.
• b. Air seasoning-Exposing the woods to air for seasoning. At first, a platform is required that
is built on the ground at 300mm height above the ground.
• Secondly, the arrangement of woods in layers. Air circulation is maintained between logs
because it helps to reduce the moisture which is important for seasoning. The environment
for this need to maintain some conditions. A clean, shady, dry, cool place is preferred.
Sometimes logs are coated by the impermeable substance to reduce extreme moisture. To
improve the quality oil coating, thick paint coating is maintained. To prevent fungal infection
logs are treated with petrol or gasoline.
• Advantage:
• Good quality of seasoned wood.
• A large amount is convenient in this process.
• Well-seasoned timber is formed.
• Disadvantage:
• It’s a slow process

47. Natural Seasoning
• Seasoning of woods or timbers using natural elements is called natural seasoning. eg.
water and air seasoning.
• a. Water seasoning-Removal of wood sap immersing logs into water flow is
called water seasoning. It is carried out on the banks of the river while thicker ends
are kept towards upstream. After that, the logs are allowed to dry. Disadvantage: It is
time consuming such as 2 to 4 weeks generally.
• b. Air seasoning-Exposing the woods to air for seasoning. At first, a platform is
required that is built on the ground at 300mm height above the ground.
• Secondly, the arrangement of woods in layers. Air circulation is maintained between
logs because it helps to reduce the moisture which is important for seasoning. The
environment for this need to maintain some conditions. A clean, shady, dry, cool place
is preferred. Sometimes logs are coated by the impermeable substance to reduce
extreme moisture. To improve the quality oil coating, thick paint coating is
maintained. To prevent fungal infection logs are treated with petrol or gasoline.
• Advantage:
• Good quality of seasoned wood.
• A large amount is convenient in this process.
• Well-seasoned timber is formed.
• Disadvantage:
• It’s a slow process.

48. Artificial Seasoning
• a. Seasoning by Boiling-Seasoning by boiling wood logs in hot water is called seasoning by
boiling. Drying is done after proper boiling. For a large amount of wood, it is done in an
enclosed place where hot steam is passed.
• Advantages It takes a short amount of time. Generally, 3-4 hours is good enough.
• Develops the strength and elasticity.
• Disadvantages It is serviceable basically for a small quantity of wood, not convenient for a
large amount.
• The cost is high.
• b. Chemical seasoning
• Reduction of moisture using salt solution is called chemical seasoning. After the absorption of
water by the solution logs are let to dry.
• Advantage It increases the strength of the timber.
• It is less time-consuming.
• Disadvantage Chemical reagents can sometimes reduce strength.
• It can cause a problem in gluing or finishing or corrosion while using.
• c. Kiln seasoning
• Seasoning of wood by using a large chamber or oven where there is a good process for the
circulation of hot air.
• Advantage Most effective and economic seasoning.

49. Kiln seasoning can be done by 2 processes such
as:-
Progressive kiln Seasoning: Wood log is entered through the kiln ant the
temperature and humidity differentials are maintained through the length of
the kiln to maintain proper drying.
Compartmental Seasoning: Its maintained by enclosed container or buildings.
Advantage: It accelerates the process because external energy is used.
d. Electrical seasoning
Dry wood is non-conductor of electricity while green timber is a conductor, so,
can pass alternating current. Thus in this method alternating current is used
for drying the cells of wood by creating heat. As electricity is used, it’s called
electrical seasoning.
Advantage:
Using this method quick drying is obtained. a French electrical seasoning
method is used to season overnight.
Disadvantages:
The equipment required is very costly.
It is an uneconomic process as a high rate of electricity is consumed.
During heating the cells of wood or timber they lose their strength and
become weak.

50. Qualities Improved by Seasoning
By seasoning, some common known qualities are improved which are mentioned below:
1. Strength
2. Hardness
3. Durability
4. Weight
5. Painting and finishing
6. Gluing
7. Resistance to insect attack
8. Electrical resistance
9. Heat content
• Precautions
• Following precautions must be taken during seasoning of timber.
• During seasoning, the moisture should be removed under an environment maintaining conditions.
• Moisture should be extracted almost at an equal rate from all logs because differentiated dryness causes
irregular shape.
• Seasoned timber should be protected from exposure to the rain and excessively high humidity during air
seasoning
• During seasoning, a proper gap between logs should be maintained for easy and uniform air or water or hot air
passing.
•