Air Seasoning - Air seasoning is usually a slow process. Sawn material for air seasoning should be stacked under shade, preferably in a shed. Three-recommended standard designs of sheds are-
1. Shed Type 1 - It consists of a roof with walls on all four sides
2. Shed Type 2- It consists of a roof with walls on three sides, north side being open.
3. Shed Type 3 -It consists of a roof supported on pillars, all sides being open.
Kiln Seasoning - It is a quick method of seasoning timber to the desired moisture content. The seasoning kiln is a chamber equipped with arrangements for heating and humidifying the drying air to desired conditions of temperature and relative humidity. Steam is generally used for heating and humidifying the air in seasoning kilns, though electrical heating.
Crossers for stacking timber in kilns shall be 30 mm to 35 mm wide and 15 mm to 25 mm thick. Crossers shall be aligned in vertical rows directly over foundation beams. The stack shall be made to fill out the entire length and height of the stacking space. Any gaps in length and height shall be suitably blocked by baffles to prevent short-circuiting of air circulation via these gaps. Kiln samples shall be chosen from the thickest, wettest and slowest drying stock in the kiln charge. Samples so chosen shall be used for selecting the drying schedule to be employed and for regulating the drying conditions at different stages during the run. A check test shall be made at the conclusion of drying for average moisture content, moisture content distribution in the section and case hardening in all the kiln samples
Schedule I covers species commonly used for packing case manufacture.
Schedule II covers timbers commonly used for light planking or for moderately heavy type of packing cases.
Schedule III covers species which include most light Inlet Side, “C furniture timber.
Schedule IV covers species which include common furniture timber.
Schedule V covers species used for furniture, constructional work or for certain special items.
Schedule VI covers species which are used for structural purposes and heavy planking.
Schedule VII covers species which include several heavy and highly refractory timbers.
OTHER SEASONING METHODS
1.High Temperature and Superheated Steam Drying - This technique essentially consists in kiln drying of timber at temperatures in the vicinity or in excess of the boiling p3int of water adopting suitable RH reduction schedules.
2.Solar drying - Solar kilns based on the ‘greenhouse’ principle. Of the two designs of this type of kiln, namely, forced air circulation and thermal circulation designs, the former is better suited for rapid and uniform drying of timber without any degrade.
3.Dehumidification Drying - This is essentially a kiln drying process in which the water vapour from the kiln is removed by condensing it as water on the evaporating (cooling) coil of a refrigerating system.
4. Pre-drying or Forced Air Drying - The method consists in forcing unheated atmospheric air or air heated to low temperatures (not exceeding about 42°C) through the timber stack by means of fans in a single pass or by a recirculating system.