“Culls,” the lowest grade, are used only upon the cheapest work. One half of the board must be usable.
In many cases the boards are graded by the width of clear stock which can be taken out. There are tables published by the different associations of lumber manufacturers which give the gradings under which their lumber has been measured and shipped, but as these vary from time to time no permanent list can be given.
The principal reason why there can be no permanent grading of lumber is that the forests from which the finest timber can be cut in marketable quantities are being destroyed faster than they can be replaced by nature. In anticipation of this condition, the Division of Forestry of the Department of Agriculture is actively engaged in organizing government forest preserves, in educating the people, and in promoting legislation aimed at the husbanding of our forests. When we consider the abundance of high grade lumber a few years ago, and the fabulous prices which the same grades now bring, it is evident that this movement should have begun during the days of our grandfathers, instead of waiting until nearly all the best lumber in the great forests east of the Mississippi had been cut, and inestimable damage wrought by forest fires.
11. The testing of lumber.—(A.) Dry, sound stock, if struck with the knuckles or with a hammer, will give a clear ringing response, while a wet or decaying piece will give a dull response to the blow.
(B.) Every kind of lumber has its peculiar odor, by which, as well as by the grain, the student should learn to distinguish the woods in common use. This may be more easily done before the wood has been thoroughly seasoned. Wood in general has a sweet and pleasing odor; if a sour or musty smell is perceptible, it indicates that decay is present.
(C.) If there is much variation in the color of timber, or black and blue spots, the stick is probably diseased.
(D.) Decay is a disease, which may be prevented by dryness or ventilation, and frequently may be cured by soaking the wood in water for several days, or by steaming. The disease of decay is cured also by chemical preservatives being forced into lumber by pressure; this at the same time prevents insects from boring into the tree.
Alternate wetting and drying will produce rot, but most lumber, if permanently submerged or if kept perfectly dry, will last almost indefinitely. Dry rot spreads to adjoining timbers, and even to those which have no connection with the one originally infected.
12. Surveying or estimating lumber.—(A.) It is the custom to consider any board less than one inch in thickness as an inch board, and anything over one inch is measured as so many inches and fractions of an inch. For instance, a board ¾” thick is surveyed as a full inch, while one which is sawed 1½” in thickness is estimated by obtaining its surface measure, and increasing it by one half. Thus, a plank 12’ long, 8” wide, and 1½” thick would have twelve feet board measure in it.
In some localities there is a sliding scale of prices which varies with each quarter inch in thickness of resawed lumber, but this is not universal.