\ FOREST PRODUCTS LABORATORY \ FOREST SERVICE U. S. DEPARTMENT OF AGRICULTURE VENEER CUTTING AND DRYING PROPERTIES VENEER CUTTING AND DRYING PROPERTIES TAMARACK Tamarack or eastern larch (Larix laricina) (Du Roi) K. Koch (8) is a email to moderate size softwood tree growing in the northeastern United States as far south as West Virginia, the Lake States, Alaska, and much of Canada (Jj. The tree attains a diameter of 1 to 2 feet (6) and a height of 50 to 70 feet above the ground. The trunk is usually straight, round and slightly taper- ing(6). The wood is fairly heavy, coarse grained, slivcry, often spiral grained, and shows strong con- trast between springwood and summerwood (JJ. The heartwood is yellowish-brown to russet- brown and the sapwood is whitish and is narrow in width (6_). Tamarack has moderate strength, stiffness, hardness, and shock resistance. The heartwood has fair decay resistance and is difficult to treat with preservative (11). The wood is reported to be comparatively difficult to ignite ( 13) . The wood shrinks moderately, but warps and checks little in drying (I). Kiln-drying schedules have been published by the Forest Products Laboratory (7). The chief uses of the wood are for pulpwood, lumber for framing, boxes, crates, railroad ties, telephone poles, fence posts, and fuel (6). Description of Logs Tested Five 8-foot-long tamarack logs were received at the Forest Products Laboratory from Aroostook County, Maine,— for veneer cutting tests. They were of moderately good quality with knots being the most common exterior defects. The logs were cut from three trees and were numbered 240, 241, and 242. Based on the logs used in this study, the main defects to be avoided in the selection of tamarack veneer logs are knots, end checks, and compression wood (6). A more complete description of the logs is given in table 1. Underlined numbers in parentheses refer to literature cited at end of this paper. "^"he logs were obtained by the Northeastern Forest Experiment Station and Joseph M. Lupsha, Utilization Forester, State of Maine Forest Service, in cooperation with the International Paper Company and the Maine Public Service Company. Report No. 1766-16 May 1961 r Maintained at Madison 5, Wisconsin in cooperation with the University of Wisconsin Agriculture - Madison Preparation of Bolts and Flitches for Veneer Cutting Two logs, Nos. 240 and 241-2, were sawed into bolts about 4 feet long for rotary cutting. Three logs, Nos. 241-1, 242-1, and 242-2, were sawed into flitches for flat slicing. Two flitches were cut from log No. 241-1, but only one from each of the other logs because of their small size. The bolts for rotary cutting were heated in water at 160° F. before being cut into veneer. Ex- perience in heating veneer bolts has shown that softwood species similar to tamarack in specific gravity, annual ring structure, and size may be heated at 160° F. without severe end checking. Small heart checks opened up during heating of the tamarack bolts, but they were confined to the portion of the bolt normally left as the core in rotary veneer cutting. Most of the veneer was smooth and fairly tight. Some of the sapwood veneer, however, was fuzzy. The flitches were heated in water at 180° F. before being sliced into veneer. Defects due to heating did not appear in the flitches nor in the veneer. Most of the veneer was smooth and fairly tight but, again some of the sapwood veneer was fuzzy. The approximate heating times required for conditioning 8 -foot tamarack bolts of various diam- eters in water at 160° F. to insure a temperature of 120° F. at a core diameter of 6 inches are as follows (3) : Log diameter Heating time ( Inches) ( Hours ) 12 5 24 30 30 48 The approximate heating times required for conditioning 8 -foot flitches of various end dimensions in water at 180° F. to insure a temperature of 160° F. at the flitch center are as follows (5): Average end dimension of flitch Heating time ( Inches ) ( Hours ) 6 4-1/2 12 17 16 29 The data in these tabulations are based on an assumed starting temperature of 70° F. If the wood is colder, additional heating time is required. Veneer Cutting Rotary Cutting The lathe settings given in table 2 were satisfactory for cutting smooth, fairly tight veneer. The sapwood veneer was smoother and had less shelling when cut with a horizontal nosebar opening larger than that used for the heartwood veneer (table 2). Most of the veneer was smooth and uniform in thickness. The knife checks were shallow in the 1 / 16-inch-thick veneer and moderately deep in the 1 /8-inch-thick veneer. Most of the knots cut smoothly and did not damage the edge of the lathe knife. Veneer containing compression wood cut smoothly. Report No. 1766-16 -2- Slicing The slicer settings given in table 3 were suitable in most cases for cutting veneer of good quality. On portions of the flitches from which all sapwood veneer was cut, however, the sapwood was fuzzy and often severely shelled. The quality and appearance of the sliced veneer was similar to that of the rotary-cut veneer. The 1 /8-inch-thick veneer had slight roughness in half of each sheet (9). In general, smooth veneer was cut when the angle between the ground face of the slicer knife and the wood rays was less than 90° ( 10). Slightly rough veneer was cut when this angle was greater than 90°. Veneer containing compression wood cut smoothly. Veneer Drying The veneer was dried in a mechanical roller-conveyor-type dryer. Drying schedules used are shown in table 4. Most of the veneer dried flat and smooth and had few splits or other drying defects. Sapwood veneer that had been cut with excessive nosebar pressure often broke apart along the annual rings during drying. Veneer, 1/16-inch thick, containing compression wood often buckled severely during drying. Veneer, 1/8-inch thick, containing compression wood, usually buckled only moderately during drying. Shrinkage of veneer dried to between 4 and 9 percent moisture content was moderate. Veneer Yields and Grades Rotary-Cut Veneer There was little loss of veneer from defects; or roundup at the lathe as three of the four bolts were nearly cylindrical. The actual board foot yield of veneer was about 19 percent greater than the log scale (Scribner Decimal C). Veneer cut 1/16-inch thick was graded ( 12) for use in structural plywood. Based on the total yield of dry veneer, an average of about 19 percent was "A" grade; 4 percent, "B" grade; 76 per- cent, "C" grade; and 1 percent, "D" grade. Rotary-cut veneer 1/8-inch thick was graded for use as box shook (14). When this veneer was clipped so as to obtain the maximum amount of acceptable shook, there was an average of about 73 percent acceptable shook 4 inches wide, based on the total yield of dry veneer. Most veneer degrade was caused by knots. Sliced Veneer Yield measurements made on two flitches (Nos. 241-12 and 242-21) showed that about 66 percent of the green flitch volume was recoved as dry veneer. Report No. 1766-16 -3- There was little loss of sliced veneer because of defects. The actual board-foot yield of veneer, measured on one of the flitches, was about 5 percent less than the log scale. Veneer, 1/16-inch thick, was graded for use as faces for decorative plywood. An average of about 13 percent of this veneer was suitable for clear faces, 30 percent for knotty faces, and 57 percent for back or core grade, based on the total yield of dry veneer. Sliced veneer, 1/8-inch thick, was graded for use as box shook ( 14) . There was an average of 68 percent acceptable shook when the sheets of veneer were clipped for grade, based on the total yield of dry shook 4 inches wide. ( Most veneer degrade was caused by knots. Stain The wet veneer developed a blue -black stain upon contact with iron or steel. The stain was easily removed by swabbing the wood with oxalic acid (3). Gluing Plywood panels of good quality were made with some of the veneer. Attractive -decorative panels were made with faces of sliced veneer, 1/16-inch thick, of both the clear and knotty grades. The panels were five-ply with the core of ponderosa pine, 1/8-inch thick, and crossbands of yellow-poplar, 1/24-inch thick. A phenolic film glue was used for bonding. Sheathing-grade plywood, 1/2-inch thick, was made with five plies of rotary-cut tamarack veneer. The core and crossbands were 1/8-inch thick and the faces and backs were 1/16-inch thick. The plywood was made with an extended phenolic glue of the type frequently used for interior-type, sheathing-grade plywood. These panels had a random knot and grain pattern, much like that seen in some Douglas-fir plywood, and were fairly flat and free from checks. Based on these limited studies, tamarack would be considered as moderately easy to glue. Finishing The decorative plywood panels made with knotty faces were filled with a neutral-colored wood filler. No filler was used on the panels with clear faces. The panels were lightly sanded and then were finished with two coats of clear lacquer. The panels were readily sanded to a smooth surface and were finished without difficulty. Appearance and Potential Use of the Veneer Tamarack plywood, faced with knotty or clear sliced veneer, makes attractive-decorative panel- ing. The knots are usually small and fairly tight, and the wood has a warm yellowish-brown color with a slight-greenish cast. Veneer containing compression wood had an orange cast with- out the greenish tinge. Sheathing-grade plywood made with rotary-cut veneer would probably be suitable for structural use (4). Based on its specific gravity and modulus of elasticity, tamarack would fall into Species Group I as listed in the Commercial Standards for Western Softwood Ply- wood (12). Rotary-cut veneer also seems suitable for box shook. Report No. 1766-16 -4- Literature Cited (1) Betts, H. S. 1945. Tamarack. American Woods Series. U.S. Dept. of Agri. Forest Service. (2) Brown, H. P. , Panshin, A. J. , and Forsaith, C. C. 1949. Textbook of Wood Technology. Vol. I. New York. (3) Downs, L. E. 1950. Bleaching Wood. U.S. Forest Products Laboratory Report No. 1705. (4) Federal Housing Administration 1958. Minimum Property Standards for One and Two Living Units. FliA No. 300. U.S. Government Printing Office. (5) Fleischer, H. O. 1959. Heating Rates for Logs, Bolts, and Flitches to be Cut into Veneer. U.S. Forest Products Laboratory Report No. 2149. (6) Forest Products Laboratory 1955. Wood Handbook. U.S. Dept. of Agri. Handbook No. 72, Forest Service. (?) . I960. Kiln Schedules and Drying Times. U.S. Forest Products Laboratory Report No. 1900-5. (8) Harlow, William H. , and Harrar, Elwood S. 1941. Textbook of Dendrology. 2nd Ed. New York. (9) Lutz, John F. 1952. Measuring Roughness of Rotary-Cut Veneer. The Timberman, Vol. LIII, No. 5. (10) . 1956. Effect of Wood-Structure Orientation on Smoothness of Knife-Cut Veneers. Forest Prod. Jour., Vol. VI, No. 11. (11) MacLean, J. D. 1952. Preservative Treatment of Wood by Pressure Methods. Agriculture Handbook No. 40, U.S. Dept. of Agri. , Forest Service. (12) Office of Technical Services, Commodity Standard Division 1961. Western Softwood Plywood Commercial Standards CS122-60. U.S. Dept. of Com. (13) Prince, Robert E. 1915. Tests on the Inflammability of Untreated Wood and Of Wood Treated With Fire- Retarding Compounds. Report of the Commission on Uses of Wood. Proc. of the National Fire Protection Assn. (14) Production and Marketing Administration; Poultry Branch 1951. Recommended Specifications for Standard Packs, Containers, and Packaging Materials for Poultry and Poultry Products. Handbook 25, U.S. Dept. of Agri. 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