. Canadian forest industries 1894-1896. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. dries and shrinks before the interior has a chance to do the same, and thus forms a firm shell or case of shrunken, commonly checked wood around the interior. This shell does not prevent the interior from drying, but when this drying occurs, the interior is commonly checked along the medullary rays, as shown in fig. 5. In prac- tice this occurrence can be prevented by steaming the lumber in the kiln, and still better by drying the wood in the open air or in a she
. Canadian forest industries 1894-1896. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. dries and shrinks before the interior has a chance to do the same, and thus forms a firm shell or case of shrunken, commonly checked wood around the interior. This shell does not prevent the interior from drying, but when this drying occurs, the interior is commonly checked along the medullary rays, as shown in fig. 5. In prac- tice this occurrence can be prevented by steaming the lumber in the kiln, and still better by drying the wood in the open air or in a shed before plac- ing in the kiln. Since only the first shrinking is apt to check the wood, any kind of lumber which has once been air dried (three to six months Fig. 5â"Honeycombed" board. The for i-inch Stuff) may checks or cracks form along the pith rays, be subiected to kiln heat without any danger. Kept in a bent or warped condition during the first shrinking, the wood retains the shape to which it was bent and firmly opposes any attempt at subsequent straightening. Sapwood, as a rule, shrinks more than heart- wood of the same weight, but very heavy heart- wood may shrink more than lighter sapwood. The amount of water in wood is no criterion of its shrinkage, since in wet wood most of the water is held in the cavities, where it has no effect on the volume. The wood of pine, spruce, cypress, etc., with its very regular structure, dries and shrinks evenly, and suffers much less in seasoning than the wood of broad-leafed trees. Among the latter, oak is the most difficult to dry without in- jury. Small-sized split ware and " rift " boards â season better than ordinary boards and planks. To avoid "working," or warping and check- ing, all high-grade stock is carefully seasoned, preferably in a kiln, before manufacture. Thicker pieces may be made of several parts glued to- gether ; larger surfaces are made in panels or of smaller pieces covered with v
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectforestsandforestry
