AIR-DRYING OF LUMBER Lumber may be air-dried at the sawmill for a few months to a year, before it is ready to ship to consuming points. The time required to reach shipping condition depends upon weather, season of the year, kind of timber, and climate. Inch pine lumber may dry to shipping condition in two months in the Southwest in slimmer; while, in the damp climate of the Gulf Coast, cypress manufacturers may find it necessary to hold lumber in their yards for a year to bring it to shipping condition.
Quick and satisfactory air-drying of lumber is secured by following certain principles which are recognized by all experienced lumbermen. These are to have solid foundations so that the piles will not settle out of shape; to have a good clearance above ground, and the piles sufficiently open to give free circulation of air; to have enough cross-pieces regularly placed to hold -the boards straight while they are seasoning; and to give sufficient slope to the piles, and have them well covered so that water will run off quickly. A careful observance of these principles will produce straight, bright stock under conditions which would result in very poor stock if the lumber were not properly piled.
There is a common theory that if timber is cut in the winter "while the sap is down," it is much superior to summer-cut timber in strength, resistance to decay, and other desirable qualities. As a matter of fact, while there are certain advantages in winter cutting, there is absolutely nothing to the notion that the sap is "down" in winter and "up" in summer. There is practically no difference between winter and summer in the amount of water which the wood of a tree contains. Winter-cut wood seasons best because it dries out more slowly and evenly, with less checking and warping, than summer-cut wood. It is also less liable to attacks of fungi, which produce decay or stain. Since the hardwoods are more difficult to season than the softwoods, the latter are less likely to sustain injurious effects from summer cutting. In the North, therefore, many operators saw mostly hardwoods in the winter and spring, and softwoods —pine and hemlock—in the summer and fall. However, many lumbermen cut timber the year round as it runs in the forest, and experience no special difficulty in either handling or marketing their stock.
A recent innovation in lumber seasoning for which much is claimed is a preliminary steaming in a tight cylinder before the lumber is piled in the yard to air-dry in the usual fashion. It is said that the steamed lumber air-dries much more quickly and with less checking and warping than does unsteamed lumber. It is also claimed that lumber cut from logs which have been in the water for some time, seasons better than lumber cut from logs which go straight from the stump to the mill. Both the steaming and the water-soaking seem to dissolve some of the contents of the cells in the sapwood, and open the wood up so that it subsequently seasons more uniformly.