>> Felling of trees:-
- The process of cutting down or felling down the trees is known as the felling of trees.
- cutting must be done at an appropriate age when it will achieve sufficient maturity.
- If the over-mature tree being cut it would have a large portion of decayed wood i.e. pith and if under matured tree cut the then large percentage of sapwood would be present. In both cases, we will get poor timber.
- The optimum age for the cutting of the tree is 5-100 years.
- Cutting should be done when the sap is at rest. Not in autumn or springs because in that season movement of nutrients will be more.
- Cutting should be done in summer in hilly areas and winter in plain areas.
>>SEASONING OF TIMBER:-
- The process of drying of timber up to the optimum level of moisture is termed as seasoning of timber.
- A newly fell timber having almost 50% water by weight hence it cannot be used directly. This water may present either in cell cavities or cell walls and may be either as sap or as moisture. Removing sap from timber is a difficult task.
- During the drying process, a condition occurs when the entire cavity water is lost but wall water still present this stage is termed as the fiber saturation point.
Significance of seasoning of timber (PROCESSING OF TIMBER):-
- To remove moisture, so that its uniform burning can be done.
- To increase its workability and resistance against deforming agencies like insects, fungi, etc.
- To reduce its weight so that transportation costs can be optimized.
- Removing moisture prevents warping and twisting during burning. Hence, helps in maintaining uniform shape and size.
- It also permits decorative treatments over it.
Two main types of timber seasoning are as under-
- Natural seasoning:- it is a very time-consuming process usually takes 2 to 4 years to make timber fit for the
work. In this method seasoning is carried out by natural air hence it is sometimes referred to as Air seasoning. This method is cheap and simple. But natural factors are really difficult to control. Hence, this became obsolete nowadays.
2. Artificial seasoning:-
I. ELECTRICAL SEASONING:- In the method of electrical seasoning timber is subjected to high-frequency alternate currents. The resistance of timber against electricity is measured at every interval of time. When the required resistance is reached seasoning process is stopped because the resistance of timber increases by reducing moisture content in it. It is also called as a rapid seasoning and it is uneconomical.
II. CHEMICAL SEASONING:- In this timber is immersed into the solution of soluble salts such as zinc chloride and mercury chloride which increases the rate of evaporation. In this method evaporation in the heart, wood is comparatively more than sapwood. Hence sections obtained by this method have a lesser tendency against cracking.
III. WATER SEASONING:- water seasoning is the process in which timber is immersed in water flow which helps to remove the sap present in the timber. It will take 2-4 weeks of time and after that timber is allowed to dry. Timber section should be placed such that a larger portion faces upstream and shorter portion faces downstream. Section obtained by this process has a lesser tendency against twisting and warping (due to removal of sap) but is observed to lose its strength.
IV. SEASONING BY BOILING:- Seasoning of timber is also achieved by boiling it in water for 3-4 hours. After boiling timber is allowed to drying naturally. For a large quantity of timber boiling is difficult so, sometimes hot steam is passed through the timber logs in the enclosed room.it also gives good results. Timber obtained by this method is observed to lose its elasticity and strength.
V. KILN SEASONING:- in this method timber is subjected to hot air in the airtight chamber. The hot air circulates in between the timber logs and reduces the moisture content. The temperature inside the chamber is raised with the help of heating coils. When the required temperature is obtained moisture content and relative humidity gets reduced and timber gets seasoned. even though It is a costly process, it will give good results strength-wise.