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LOSSES INCURRED IN SEASONING LUMBER

An attempt to summarize our annual national losses in the seasoning of lumber is recorded in the Report of the National Conference on Utilization of Forest Products, which conference was held in Washington, D. C., on November 19 and 20, 1924. This report printed an interesting digest of wood wastes by Rolf Thelen, of the Forest Products Laboratory, which wastes may be tabulated as follows, in equivalents as stated, of billions of feet of standing timber:

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Regarding seasoning losses, the following statement was made:

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Mechanical defects such as checks and cracks, loosening of knots, warping, splitting, twisting, cupping, etc., are in general caused by the seasoning process and are usually termed " seasoning defects." They result in a reduction in the quality of the board or in the salable volume, or both. They may occur at almost any period during the manufacture and use of wood. The principal losses, however, occur at the sawmill and at the remanufacturing plant because it is at these points that most of the seasoning is done.

Seasoning losses occur also in forms of material other than lumber, such as structural timber, sawed and split vehicle stock, handle billets, and cooperage. Staining may occur in the log itself. A reduction in the heat efficiency of fuel wood due to incomplete seasoning represents an important waste.

The sum total of the various seasoning losses represents over 1,000,000,000 cubic feet of standing timber per annum, or more than 4 per cent of the forest drain.

After enumerating and describing these various wastes, attention is directed to the elimination of such as are preventable, and in this section seasoning losses are discussed in the following language:

It is not commercially feasible at the present time entirely to avoid degrade in seasoning lumber, because a perfected seasoning operation is too long and too costly.

Degrade can be reduced, however, even under fast-drying schedules. In southern pine, for instance, research has devised 72-hour kiln-drying schedules, which have reduced degrade from about 20 to 5 per cent in the upper grades and from about 30 to 10 per cent or less in the common grades.

A careful analysis of degrade losses occurring in the air seasoning and kilndrying of many kinds of wood indicates that avoidable wastes are large, and that the present average seasoning practice, compared to the best commercial practice, is poor and could be much improved through the employment of competent operators and the maintenance of drying equipment in first-class condition. Still further saving could be effected by remodeling antiquated kilns and installing modern equipment.

About two-thirds, or two-thirds billion cubic feet, of the present losses are estimated to be avoidable. This estimate applies only to sawed products.

A billion cubic feet of timber is equivalent to 12,000,000,000 board feet, and the two-thirds saving estimated as possible in the last paragraph would be equivalent to 8,000,000,000 board feet. Assigning to this timber a value of $5 per thousand board feet as standing timber would give a value of $40,000,000 as the total saving possible by better methods of seasoning, universally applied.

This is equivalent to a preventable loss through degrades of a little over $1 a thousand, averaged over the entire annual production of approximately 38,000,000,000 board feet. Some of the figures quoted may seem large at first glance, but this final figure of a little over $1 preventable seasoning loss on our entire lumber production seems well supported by such estimates of degrade losses as have been made. Certain tests on some species have shown degrade losses of less than $1 on some common grades, spread upon the entire production of that grade concerned in the tests; but in other items degrade losses have been so estimated running up to more than $11 per thousand feet.

Another light on the footage loss is supplied by the following quotation from an article entitled "Log Scale Versus Lumber Tally," by M. Bradner, Office of Forest Products, and Philip Neff, United States Forest Service, Missoula, Mont., reprinted from the Timberman, Portland, Oreg. (with no information regarding date of original publication). The following statement appears:

A good average figure for this shrinkage “from chain to car" is 3 per cent. This figure, which represents the average reported by numerous mills over a period of years, has been adequately substantiated by actual depreciation studies carried on by the Forest Service in connection with air-seasoning investigations.

It is obvious that this is a loss of footage only, which does not take into account the other and more important loss of value by degrade, incident to seasoning. Some part of the loss results from remanufacturing operations in the planing mill not due to seasoning defects. Most of the reduction in footage because of seasoning defects takes place in dressing and working, aside from the throwing away of culled boards. If the loss in footage from seasoning defects is taken as 22 per cent, and if the average mill value of our lumber product may be taken as $30 a thousand, this loss in footage alone would amount to 75 cents a thousand feet on the entire lumber production, leaving a material additional loss to be added for lumber reduced in value but not footage.

Just now the total of national waste in seasoning of lumber as distributed between air-dried and kiln-dried product is not known, and it seems difficult to form any conception. Figures derived from some of the early works on dry-kilning, in which production figures are used as a base for estimation, indicate that approximately 50 per cent of the lumber produced in 1913 was dry-kilned. This status appears to be accepted in The Kiln-Drying of Lumber, by Koehler and Thelen, published in 1926, in the statement appearing on page 10: "Furthermore, most of the 20,000,000,000 feet of lumber kilndried each year consists of the upper grades."

The precise quantity of lumber that is kiln-dried is not known, and there is uncertainty as to the exact percentages of high-grade lumber dried in kilns. There are two facts that seem to be certainties in this direction, namely, that the national production of lumber is chiefly in No. 1 common grade and lower, and that the degrade in seasoning is heavier on the common lumber, whether airseasoned or kiln-dried. It is also very likely that the greater proportion of common lumber is air-dried; even in the species where kiln-drying of common grades had gone to the greatest extent, as

in southern pine, it is improbable that kiln-drying of common predominates over air-drying in the total volume of annual product.

Whatever the national loss from preventable wastes in seasoning may be, it is by no means evenly distributed. It is the difference between poor practice and better practice which is being demonstrated, and there are many manufacturers in all sections and in all species who are using these better methods whose more general adoption it is the chief purpose of this report to encourage.

The questionnaires sent to lumber manufacturers brought replies from mills reporting an annual production of nearly one-tenth of the entire production and also stated what percentage was air-dried, kiln-dried, and sold in green form. Applying the same percentages to a national annual production of 38,000,000,000 feet, the division would be about as follows:

Air-dried.
Kiln-dried

Marketed in green form___.

Total___

Feet

15, 958, 000, 000
15, 153, 000, 000
6,889, 000, 000

38, 000, 000, 000

It is probable, however, that these mills had a larger percentage of kiln-dried product than the national average, as they were mostly mills of larger than average size, the average annual production being 44,700,000 feet mill. per

SEASONING OF LUMBER IN SAWMILL YARDS

Probably the major portion of the lumber annually manufactured is seasoned in sawmill yards. Some portion of this lumber is kilndried, following the yard seasoning-probably over half the hardwoods and a rather small proportion of the softwoods. Softwoods are air-dried in order to bring the lumber to a dryness suitable to the use for which the stock is intended; most of the rekilning is done at factories, though a great deal of softwood goes into various factory uses where more thorough drying than good air-drying is not needed. Hardwood stock for sawmill kiln-drying is generally taken from the yard in a partly dried condition, particularly when the sawmill is shut down. Softwood stock, almost without exception, is dried green from the saw without being stacked in the yard at all.

Much of the lumber that is air-dried could be kiln-dried with less degrade loss, and at an actual lower cost, all factors considered. In some thick hardwoods kiln-drying is so slow as to cost more than airdrying. Kiln-drying is gradually replacing air-drying each year as dry-kiln equipment is expanded. But the replacement process is slow, even in fields where the advantages of kiln-drying over airdrying are most obvious; for kiln-drying requires a large investment in dry-kiln equipment which in some cases might not be justified by the operating life of the plant as limited by its timber supply. Air-drying requires only suitable yard space and a moderate investment in pile foundations, stickers, etc., all of which consist of sawed material that the mill itself can supply, and usually from defective and unsalable stock. Air-drying requires the tying up of capital in lumber piles for the period required for drying; the kiln-dried material can be rapidly put into a marketable condition of seasoning.

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In some species of wood, as in cypress, air-drying is the preferred seasoning, and many of the mills having dry kilns use them for final drying of air-dry stock; in the hardwoods in general, while kilndrying could be done green from the saw with considerable reduction of seasoning losses, the present practice of operating the mill without dry kilns and air-drying the product, most of which will be later kiln-dried somewhere in factory dry kilns, is firmly established, with a very few exceptions among the leading mills, where both dry kilns and planing-mill equipment have been added following a policy of marketing the product in more refined forms than as rough-dry lumber. Many of the long-established arguments against kiln-drying direct from the saw may disappear with a wider use of controlled kilns and careful kiln operators. In any species where kiln-drying must be done very slowly to avoid damage to the stock the advantage in cost over air-drying is reduced or reversed. The kiln-drying difficulties mostly appear in drying from a green condition to 40 per cent, although drying at low temperatures may easily be accomplished; and some manufacturers are successfully using a combination method of partial kiln-drying followed by yard piling and air-drying on some southern hardwoods. This plan succeeds in avoiding blue-stain damage on susceptible species. Such stock, of course, can be given a final kiln-drying. This combination method is often cheaper than seasoning by either kiln-drying or air-drying exclusively and produces better quality and less degrade loss in woods adapted to the process.

SAWMILL YARD ARRANGEMENT AND LAYOUT

A sawmill lumberyard must, of course, be convenient to the mill, separated only by the space required by insurance rules, and the choice of a sawmill site involves considerations which often dictate a site unfortunate from the yard viewpoint. Convenience to water is an important consideration, especially if a sawmill pond is a part of the plan; and the result is often location of the yard on low ground, or perhaps in a narrow valley with hills all about to shut out breezes. Recent southern floods were able to sweep many sawmill yards which could have found higher ground in the immediate neighborhood; in some cases it would be better to pump what water the mill needs rather than be inundated in it during flood seasons.

The site chosen for a sawmill yard should have good elevation and drainage; if the site is low and swampy, it should have a filling, which should be of earth or cinders, never of sawdust or mill trash. Sawdust might be used, perhaps, for a deep fill where it is possible to cover it over with at least 2 feet of dirt; but nearer the surface than that it will usually have in it enough of fungous decay to be a bad source of infection for lumber piled near it.

Cinders make a good fill under lumber piles, because they discourage the growth of weeds. Sand is even better; the yard of the Long-Bell Lumber Co. at Longview, Wash., is largely built on a site filled with sand dredged from the river, and the piles being rather openly spaced, the sand surface gets a good deal of sun and radiates heat so freely that lumber in the bottom of the piles dries more rapidly than that in the middle height, an unusual and very desirable condition. A California manufacturer reports the adop

tion of wood ashes and cinders for yard filling because it kills weeds, and that in time this will be extended to cover the entire yard.

A lumberyard is usually laid out with a system of parallel main alleys, with lumber piles fronting them on either side; with rear alleys between the main alleys, not usually used for highways, but

FIGURE 1.-Diagram of systematic layout and numbering of alleys and piles in a lumber

yard

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constituting an open space and dividing the yard into squares or blocks like those on city streets. Identifying the main alleys with names or letters, and numbering the piles on each alley, even numbers on one side and odd on the other, carrying the numbering system alike on each alley, so that pile 21 on alley B will be directly across from pile 21 on any of the other alleys, gives a convenient identifying key for all the piles in the yard. (Fig. 1.)

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