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A scientific study of wood seasoning
process is important, as a large number of commercially important timber
species is very problematic to seasoning. Climatic conditions
also are very exacting for various wood works such as joinery,
furniture, handicraft products etc.
During recent years the need of seasoning in timber
has become imperative due to the compulsion of use of timber from short
rotation plantations.
The Wood Seasoning branch undertakes research work related to the
drying behavior of wood, study of shrinkage and wood-water relation ship
and evaluation of kiln drying schedules. Other priorities include
investigation for suitability of Indian timber for industrial uses such
as pencil making, wooden accessories used in cotton & jute mills, and
shoe lasts as well as investigation of bending behavior of different
timber species for making bent wood articles.
Wood, a renewable material, occupies a prime position as a raw
material, Its versatile Nature has made it unique in many applications.
In most of the uses of wood, longevity of wood is very important.
Green Wood in growing trees
contains considerable quantities of water/moisture. Most of this
moisture has to be removed in order to obtain satisfactory performance
from the wood in use. Freshly felled wood contains moisture roughly
100 percent based on the oven dry weight of wood.
A well seasoned piece of wood should on other hand contain only 10 to
12 percent moisture. An important object of seasoning is to dry the
timber to the equilibrium moisture content before use, so that gross
dimensional changes through shrinkage, which inevitably occurs in green
wood as it tends to attain equilibrium with the surrounding atmosphere,
are eliminated.
How Seasoning is done ?
The method and technology we use is
"KILN", which happens to be the most energy intensive amongst
wood processing operations claiming an estimated 50-70 percent of
the total energy consumed in manufacturing wood products. The timber is
stacked in the chamber.
Then with Air blower heat
exchanges in chamber at pressure. Timber is kept in chamber for 6 to 12
days as per its fiber property. These removes all possible unwanted
moisture through fibers.
The seasoning Kiln is a chamber equipped with arrangements for heating
and dehumidifying the drying air to desired conditions of
temperature and relative humidity and its circulation over the surfaces
of timber stacked inside. Fans are used for faster circulation of air.
Benefits of Seasoning
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By seasoning timber, "Movement"
in the component of the finished products, relative to the dimensions at
the time of fabrication, is kept to a minimum. Thus seasoning is the
first step towards realizing maximum attainable dimensional stability
from any timber during use.
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Considerable losses through
cracking, splitting, warping etc, which are liable to occur while
using green timber under inevitable exposure to surrounding uncontrolled
climatic conditions, are avoided by carrying out proper seasoning under
controlled drying conditions prior to use. This is of great importance
in timber utilization in India where the climatic conditions vary
considerably at different times during the year.
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Seasoning protects timber against
primary decay, fungal stain and attack by certain kinds of insects. The
organisms, which cause decay and stain, generally can not thrive in
timber with moisture content below 20 percent. Seasoned wood is
less susceptible to decay than a green wood in indoor use.
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Seasoned timber is lighter and hence
the transport and handling are easy and the costs are reduced.
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Seasoned timber is stronger than the
green timber in most of the strength properties.
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Finishing, coloring/painting
& gluing is resulted better in seasoned & processed timber than in green
wood.
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The electrical and thermal
insulation properties of wood are improved by seasoning.
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Seasoning enables substantial
long-term economy in utilization by minimizing replacement, besides
rationalizing the utilization of our timber resources.
Most species of freshly felled
timber contain 100% or more moisture in it. For retention of
shape and size of manufactured article and make quality product, timber
should be seasoned and the moisture contents to be brought down to level
in equilibrium with the surrounding atmosphere (normally 6% to 8%).
Seasoning is done in Scientific way to ensure perfect seasoning under
controlled. Fans are of light weight having variable pitch,
dynamically balanced and reversible and that gives equal air flow in
both sides of the wood stack ensures equal drying of wood.
The drying of wood takes place by
the application of temperature humidity cycle. Drying process is checked
and monitored time to time by the use of moisture meter handled by
qualified operators.
About Wood
India is a tropical country and has
more than 80 species of wood.
Following are a few varieties of
timbers commonly used for producing hand crafted wooden products:
Pine (Abies Pindrow), Sheesham (Dalbergia Sissoo), Haldu (Adiva
Cardifolia), Rubberwood (Hevea Brasiliensis), Kadam (Anthcephatus
Chinensis), Kanju (Haloptelea lategrifoha), Gamari (Cmelina Arborea) and
Mango (Mangeferia Indica).
'The use of mango and rubber woods is increasing as these are plantation
woods, Moisture content in wood also plays a critical role in quality
and finish of the product. Ideal moisture content of standard wood is
6 to 8%.
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