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and under. The wider spacing is used in redwood, California pine, southern hardwoods, North Carolina pine, and southern pine. Of those mills, 19 increase the space for wider lumber, 10 give the bottom wider spacing, and 17 increase the spacing on lumber piled during or just previous to the season of slow drying.

Of the replies received to the questionnaire, 13 showed no use of self-sticking in the yard, and 46 showed self-sticking of a varying percentage of the yard product, ranging from 25 per cent or under to 100 per cent. Of these mills, about half the product is self-stuck, and the remainder (usually the better grades of lumber) is put on special stickers. North Carolina pine was the only species for which

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FIGURE 19.-Improved jack for use in passing lumber up to man on the pile. A bar with an iron spike is usually employed but defaces the lumber, which the corrugated form of this face will not do. Note the double swivel so that the face can always turn flat to the board. Photographs courtesy of Forest Products Laboratory

no reports showed self-sticking, and it was reported by less than onethird of the southern hardwood mills. Self-sticking is quite commonly used for northern hardwoods. Of the 42 mills reporting on this subject, 5 had a width limit of 4 inches for crossers, 8 reported a width limit of 6 inches, 5 set it at 8 inches, 4 at 12 inches, and 20 had no specific limit.

In the West the practice is sometimes followed of piling 8 and 10 inch widths together and 6 and 12 inch, selecting the crossers from the narrower widths, which reduces the amount of degrade somewhat, but not so much as would the use of narrow special stickers. Degrade is especially heavy in the boards used as crossers, mostly in the form of surface checking occurring where they are left fully exposed across the spaces between the layer boards. They

also dry more slowly than the layer boards, because so much of their surface is covered.

One of the inquiries in the questionnaire was intended to develop information on this point, and 13 of the replies indicated the piling of two or more different widths together, self-stuck with the narrowest width of the mixture.

The individual manufacturer can test the matter for himself by comparing the results of self-crossed piling with those test piles where special stickers only wide enough to carry the load are used. The advantage of special stickers is greatest on the better grades of stock, where degrade losses count up faster. Self-crossing is especially undesirable in species subject to blue stain, which is apt to appear seriously in boards covered up by wide-sticker crossings.

In some sections a different and narrow stock is used for stickers, but after being used once or twice for this purpose, or in some cases for a year or two, it is sold as commercial stock. In California 2 by 4's are much used for this purpose, being dressed before sale to remove the sticker marks; 1 by 4 and 1 by 6 are sometimes used in like manner. The sticker material is green when first used and liable to cause more stain in species subject to stain, though this influence does not seem to be evident in western pine, according to figures given in the inland empire air-seasoning study. The lumber piled on the green crossers also seasoned to 15 per cent moisture content in 11 weeks, against 12 weeks for new dry crossers and 11 weeks for old dry crossers.

It appear from replies that at 28 mills narrow crossers of some commercial size are used for a time and then sold.

Some attempt was made to obtain an idea of the amount of additional degrade occurring in self-stuck lumber over that for which special stickers were used, but the replies were not very definite. A good many of them stated that no additional degrade was apparent, while others stated that no degrading occurred in the low grades for which self-sticking was used. Five of the replies estimated the additional degrade at under 25 per cent; 2 stated that it was considerable, 2 designated it as heavy, and 2 estimated it at little. Inquiry as to the amount of degrade in boards used as crossers, in excess of that occurring in boards in self-stuck layers, brought replies estimating this excess at 25 per cent or under, at 25 to 50 per cent, and a statement that it was "heavy."

Even where special crossers are used there is a new set of variables to consider. The first question is as to species; and where blue stain is present selection should be made of some species not subject to stain, or at least of heartwood, which blue stain rarely infects in any species. In the sections where yellow popular is manufactured many millmen have preferred hemlock for stickers as not so likely to mark the lumber with stain. There are many lumbermen also who believe that a sticker is better if of some porous wood which will readily absorb moisture from the lumber, rather than from a harder and more impervious species. In an operation cutting a single species the stickers will probably be made from that species. Sometimes it is possible to bring in logs of some species that is not commercially salable and yet will make good sticker material and saw them especially for that use.

The questionnaire replies indicated the use of the same wood for stickers in most cases and little effort to employ or to discover some more suitable species. Some of the reports from California, however, indicated a preference for white fir for stickers where it could be obtained, and a secondary preference for Douglas fir, for stickers for California pine and other softwood species; and in Wisconsin and Minnesota tamarack is sometimes used to stick other woods.

The next question will be as to width and thickness. Stickers are rarely sawed less than an inch thick, and when sawed thinner it is done deliberately to slow down the drying rate in the pile in species where this is desirable to prevent end check, especially in the fastest drying season. On the other hand, they may have a thickness standard of 14, 12, or even 2 inches; and while these thicknesses are used more for 2-inch stock and thicker, they are employed to a considerable extent even in the piling of inch lumber, especially in California, where some firms use 2 by 4 stickers even for inch lumber, selling the stickers afterwards for dimension. The California airseasoning study describes as ideal practice in the pine region the use of No. 1 white fir 2 by 4 for stickers, using them two or three years and then surfacing and selling for dimension. A diagram published in that report indicated that a 1-inch sinker redwood on 8/4 stickers reached 15 per cent moisture content in a little less than 10 weeks, while it took nearly 11 weeks on 6/4 stickers and over 13 weeks on 4/4 stickers. A similar test reported in the Inland Empire air-seasoning report was made between piles with 2 by 4 stickers in the lower third and 1 by 4 stickers above, and other piles with 1 by 4 stickers all the way. At one yard the more open pile seasoned to 15 per cent moisture content in 2 weeks as against 3 weeks for the other pile in a fast-drying season; in another yard the open pile took 11 weeks, starting in October, as against 26 weeks in the other pile; in a third yard both kinds of pile seasoned to 15 per cent moisture content in the same time, 3 weeks. One California pine manufacturer uses 3 by 4 fir stickers and turns them edgewise on piles that are to go through the slow winter months, but it is doubtful whether the results justify the added cost.

It is desirable, of course, to have but one standard thickness for special stickers, but this is not good practice where thicker stock is air-dried as well as inch. The chief cost of thicker stickers is not in the extra material they contain but rather in the added amount of piling space their use requires. It might be well to have 4/4, 6/4, and 8/4 for standard sticker thicknesses and use the thicker ones in pile bottoms with inch stickers in the upper portion where this secures more even drying in the bottom of the pile, in addition to their use generally for thick stock. The manufacturer who will make some tests on this suggestion will probably secure some worthwhile results.

The width of sticker should be enough to support the load carried without crushing the sticker or denting it into the surface of the lumber, for even though the sticker marks may be removed in dressing, the area below the sticker may have been compressed and may subsequently swell and shrink by an amount different from that of adjacent areas, with a resulting variation in thickness along the length of the board. In addition to the factor of compressive strength of the

stock as related to sticker width is the factor of weight. Thus, while the compressive strength of a wood like western red cedar, for example, may be low, the lightness of the wood produces a smaller load on the stickers than would oak, for instance. These considerations come in both the softwood and hardwood groups. The heavy hardwoods do not dent readily, and 1 by 3 or even 1 by 212, 1 by 2, an dsometimes 1 by 12 inch stickers are commonly used. In piling softwoods 1 by 4 inch stickers are commonly used, sometimes in cases where 1 by 3 would carry the load. The wider stickers, however, stay straight better and are less subject to breakage.

A study of the sizes reported for special stickers shows some interesting facts. Out of 42 replies giving the information, 28 show an exclusive use of inch thickness for stickers, except that 2 of the mills make some use of 2-inch thickness for thicker stock. The only thickness reported in use for western (Pondosa) pine is 111⁄2 inches, by 1 mill; 9 others reported the use of stickers 2 inches thick for all stock, except for 2 mills where stickers 34 by 4 are reported as being liberally used for thick lumber. The three other mills which report using a 2-inch minimum sticker thickness include one in northern white pine and two in southern pine.

Reports of sticker widths show a somewhat narrower variation. Widths of 1, 114, 112, and 134 inches are reported by one southern hardwood manufacturer, and for no other species, except one North Carolina pine manufacturer uses the 1 by 112 inch size. The 1 by 2 inch size is used by two southern hardwood mills and also by one southern pine manufacturer and one Douglas fir manufacturer. The 1 by 4 size is the most popular and is indicated in 13 replies, one for southern hardwood and the rest for various softwoods. This is also the most popular width in the 2-inch thickness, the 2 by 4 being indicated in 9 replies, 7 being for California pines, 1 for North Carolina pine, and 1 southern pine.

Stickers should be as even in thickness as possible, but sawmill stickers are very rarely run through the planer to size them. It is general belief around sawmills that rough stickers mark the lumber less, though in factory practice both yard and dry-kiln stickers are usually dressed but are used mostly on product already partly seasoned.

*If blue stain appears in the sticker marks on lumber, the stickers will become surface infected, even if of wood that the stain fungus does not attack; and such stickers can become sources of infection in the next pile on which they are used. In such cases new bright stickers are preferable to old black ones, and their useful life may be curtailed considerably. Stickers, however, are often given far better opportunities of picking up stain infection during their idle periods than while in use, by being in careless contact with the ground, rubbish, etc. Stickers will keep straight and in much better condition if they are stored in suitable racks when not in use, instead of being left in helter-skelter piles here and there. Instances are reported where sawmill stickers have been used for 30 years; usually it is better to replace them with new, bright stickers at a less advanced age.

In piling hardwoods the stickers are usually spaced more closely than for softwoods, to hold the lumber straight and give it less opportunity to warp or cup between the sticker lines.

In a western fir yard three cross foundations are used under the piles, the front one at the ends of the lumber but the rear one in about 2 feet.

Undoubtedly more lumber is piled with three lines of stickers than in any other way in all softwood air-drying, and this is the practical minimum. Where sticker damage results it is better to have the damage appear in fewer places on the board, and this is made an argument for using only three stickers in piling shop lumber, because longer cuttings can be secured between sticker marks if damage occurs in them. This theory is chiefly applicable to self-crossed stock where sticker damage is more certain to occur. Additional stickers are not justified unless they produce an actual improvement in results. The only air-seasoning study that shows any tests on this matter is that for the Inland Empire, which was made on white pine No. 2 common 1 by 8, 16-foot. Lumber piled with three or four crossers and piled in August dried to 15 per cent in 14 weeks, as against 13 weeks for lumber with 5 crossers. The degrades were 3 crossers, $1.83; 4 crossers, $2.09; 5 crossers, $1.91. Increasing the crossers increased chiefly the stain and season checking and also increased slightly the percentage of final moisture content, especially in the bottom of the piles.

Of the replies received, 6 indicate the use of a minimum of 2 stickers for the shorter lengths, with either 3 stickers (5 mills) or 4 stickers (1 mill) for longer lumber. Thirty replies show the use of 3 stickers as a minimum, 12 using this number exclusively while 17 use 5 stickers, and 1 mill 6, for the longer piles. Five mills report the use of a minimum of 4 stickers, 3 using this number exclusively (1 southern hardwood and 2 southern pine) while 2 mills (southern hardwood and cypress) use 5 stickers for longer lumber. The minimum number of stickers reported for redwood (2 mills) is 5, with 6 for longer lumber, while 1 southern hardwood manufacturer uses 5 to 9 stickers.

PROJECTION OF END STICKERS

It is quite common in piling both softwoods and hardwoods to project the stickers out beyond the ends of the boards, thus protecting the ends from the sun and wind and reducing end checking, which is especially apt to occur when the stickers are in a few inches. There are some, however, who prefer to pile northern hardwoods Iwith the stickers a little back from the ends, because where the stickers project the crossings catch too much rain and are liable to develop end-dote in species subject to it.

On hardwoods the narrow stickers used can not be projected very far, and an inch or half inch is considered sufficient. A 4-inch sticker on softwoods can be set out 2 inches if desired, and where 8-inch lumber is self-crossed the crosser is sometimes set out 3 or 4 inches. Sometimes wider end stickers are provided to allow for liberal projection.

Of 56 replies indicating the placement of the front sticker, exactly half the number place it flush with the ends of the boards; 10 indicate projections of one-eighth to three-fourths inch; 11 state 1 inch; one, 11⁄2 inches; two, 2 inches; and one, 4 inches.

Where lumber is piled in separated lengths the rear sticker is often set out to protect the lumber ends, especially in far western piling.

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