In air and kiln seasoning, time depends on the density, thickness and water content of the wood. It is not advisable to use green, freshly cut timber for carving. The cells and the cell walls of this timber contain water. It is the process of drying out the free water in the cells, and the partial drying out of water in the cell walls, which is known as 'seasoning'. It is obvious that when this water which is after all a part of the tree's composition is removed, shrinkage is bound to take place. Therefore the process must be controlled if distortion, cracks and splits are to be avoided. The two main methods of seasoning are air seasoning and kiln drying. The former is a slow method. For instance, with 2 inch planks it will take over six months of good drying weather to reduce the moisture content of twenty per cent of their weight. For timber used in heated buildings it is necessary to reduce the moisture to about ten to twelve per cent. The process of seasoning wood in a modern kiln can be achieved in a matter of weeks. In the case of tropical woods, air seasoning is favored, for periods up to two years. These can then be finally dried by the kiln method. There are a few woods that cannot be kilned at all as the cell walls of the wood collapse and render the wood useless.

The kiln

Very briefly, the kiln is a brick-built room with heating pipes generally in the ceiling. Fans are installed to keep the air moving and steam is introduced through a number of jets. The wood is stacked horizontally in such a way that the air can circulate freely. The planks themselves rest on sticks or wood bearers of 1 inch X 1 inch, spaced approximately 4 ft. apart for planks that are 2 inch thick or more. Regular tests of moisture content during kilning are made and the drying process is controlled by varying the humidity and the heat.

Air seasoning

Timber deteriorates if left on the ground and exposed to the elements. In air seasoning the timber is stacked, as in kiln drying, in such a way that the air can circulate. The stack should not be more than 6 ft. wide. A well-drained site is chosen and brick piers are built not less than 9 in. in height and preferably more. These piers are approximately 9 inch square and are spaced 2 ft. apart. Timber cross members 4 inch X 4 inch are placed on the piers. Strength is given by laying further heavy bearers along the whole length of the stack. The planks to be seasoned are placed horizontally on the foundation, each plank separated from the other by 1 in. X1 in. sticks. It is important that the wood should be kept level and sagging prevented. Therefore, the sticks are placed at intervals of 2 ft. to 4 ft., according to the thickness of the planks. The stack is left open but covered by a sloping roof with a good overhang. The ends of the planks should be protected by bituminous paint. In reasonable weather, 2 inch planks of softwood stacked in the spring would be seasoned by the autumn of the same year. Hardwoods should be stacked three months earlier.

We need to treat the wood according to the season. As wrong treatments of the wood can really damaging the wood, the carved will not come as good as we expected.