Properties of Imported Tropical Woods

1 PROPERTIES OF IMPORTED TROPICAL WOODS_ By B. FRANCIS KUKACHKA, Botanist Forest Products Laboratory,2 Forest Service U.S. Department of Agriculture INTRODUCTION The descriptive text and tabular data compiled such as birch and teak in connection with totally here have been drawn freely from a wide variety unrelated species is bad practice and only adds of sources, but special credit is due the publica- to already existing confusion of names in the wood- tions of the British Forest Products Research using industry. Laboratory and those of the Yale University School The pair of capital letters after the species of Forestry. name serves as a quick reference to the broad Species descriptions are arranged alphabetical- area of origin as AF (Africa), AM (Latin America), ly by generic names. The generic name may be and AS (Southeast Asia). followed by a specific name when the latter is An index of common names with their botanical the sole or principal name used in the timber equivalents is included at the end of this trade. When a number of species are involved report. and it is generally not practical to identify the The average weight of the woods described is precise species from the wood alone, the generic given in pounds per cubic foot and at a moisture name is followed by the designation spp. content of 12 percent, unless otherwise indicated. With well-established species only a single The term “texture” refers only to the diameter common name has been applied, even though it of the pores. may have many local or vernacular names, Kiln schedules for foreign woods are given in particularly if the species has widespread distri- British Forest Products Research Laboratory bution. Where two or three names are indicated, Leaflet No. 42, “Kiln-Drying Schedules,” revised they usually refer to the name in use in the 1959. The schedules differ somewhat from those several areas of principal production. Common in Chapter 8 of “Dry-Kiln Operator’s Manual,” names which are inappropriately applied and are Agriculture Handbook 188 (1961). Table 1 (at end generally misleading have been avoided as much of report) lists the British schedule recommenda- as possible. The use of generic common names tions for 4/4 to 6/4 lumber, the nearest U.S. 1Presented at the Conference on Tropical Hardwoods held at the State University College of Forestry, Syracuse University, August 18-21, 1969. 2The Laboratory is maintained at Madison, Wisconsin, in cooperation with the University of Wisconsin. schedule from the Dry Kiln Operator’s Manual to stress relief in the lumber during sawing and for these same sizes, and a suggested U.S. the resulting burning and dulling of the teeth schedule for 8/4 stock.3 This particular difficulty is sometimes attributed Statements relative to durability refer only to to the presence of silica, even when silica is not heartwood and under conditions favorable to present. Silica, when present, may have a pro- deterioration. Sapwood is always nondurable under nounced dulling effect on all cutting edges and exterior use conditions. Wood kept continuously this becomes more pronounced as the wood is dry is not subject to attack by fungi although the dried to the usual in-service requirements. sapwood of certain species may be attacked by Strength values are given in table 3 for green powder-post beetles. wood and in table 4 for seasoned wood. The The term “in-service,” when mentioned, refers values are based on the ASTM or 2-inch standard. to the shrinkage and swelling or “movement” of The values published by the British Laboratory wood that may occur under conditions of use. It in their Bulletin No. 50 are based on the 2-centi- refers to interior use in the major part of the meter standard and are not directly comparable United States and the values, when cited, apply to with those based on the 2-inch standard. The unfinished wood. Finishes do not prevent “move- British values cited in tables 3 and 4 have been ment” but retard to varying degree the rate at converted to the 2-inch standard using the con- which moisture is lost or gained. The values version factors recommended in their Bulletin given in table 2 represent total shrinkage from No. 50. the green to the ovendry state and are based on the dimensions when green. Such values have ALBIZIA FALCATARIA As limited application and do not indicate the degree Batai of “movement” that may occur between different levels of relative humidity or the ratio of shrinkage This species, originally described from the that occurs during different stages of drying. It Molucca Islands, is now commonly found in is unfortunate that so little “movement” data are cultivation throughout the tropics of the world. available with respect to the species in everyday The tree has been utilized in Malaysia for the use. afforestation of degraded and idle lands, and in The machining of wood perhaps presents more Central America it is replacing the silk-oak problems than any phase of conversion from the (Grevillea) and native species used for shade log to finished product.. Lumber that is straight trees in coffee plantations. This species has grained and free of all defects is, of course, the shown remarkable growth in several plantations ideal material to the machine operator. Problems on the islands of Kaual and Hawaii. Data pre- begin to mount when a user is confronted with sented here are based primarily on the timber the necessity of machining species with which he obtained from these Hawaiian plantations. is totally unfamiliar. With respect to tropical Synonyms of this species are A. moluccana and species he will be confronted with considerable A. falcata. variation in density, degree of interlocking and Heartwood and sapwood not clearly distingulsh- variable grain, silica content, and tension wood, able in all trees; wood light colored with a very all of which can be very troublesome in species pale brown, pinkish, or yellowish cast. Desch of lower density. Interlocked grain is character- reports the Malayan-grown wood with grain deeply istic of the majority of tropical species and pre- interlocked and spiral: the texture rather coarse sents difficulty in the planing of quartered sur- and even. The Hawaiian-grown material was faces unless attention is paid to cutting angles and essentially straight-grained and, although inter- sharpness of knives. Tension wood may account locking was noted, it was rather shallow. The for rough surfaces, which may be referred to as wood weighs about 24 pounds per cubic foot. fibrous, fuzzy, or torn. It is also frequently American basswood (Tilia americana), of the responsible for the pinching effect on saws due same average specific gravity as batai, exceeds 3John McMillen of the U.S. Forest Products Laboratory, Madison, Wis., provided this abstract of Leaflet No. 42 and the U.S. schedule suggestions. The British schedules may be purchased from the British Information Service, 845 Third Avenue, New York, N.Y. 10022. FPL 125 2 the latter in static bending and compression ALBIZIA LEBBEK AS Parallel to grain at the 12 percent moisture Kokko, Siris content level; batai is slightly superior with respect to side hardness and maximum shearing Albizia lebbek. which is native to India, Burma, strength. Pakistan, Malaya, and the Andaman Islands has In Malaya, batai is said to dry fairly rapidly frequently and very erroneously been referred to without serious degrade; the most common defect as “Indian walnut.” The names kokko and siris observed was bowing. Lumber of 5/4 thickness are well established, well known, distinctive of was air seasoned in 6 weeks and 4/4 material the species, and should be used consistently in was well dried in 4 weeks. None of the material the U.S. trade. was reported to have developed any splits or Several other Indian species of Albizia occur checks. within the range of Albizia lebbek and are difficult The wood is said to be abrasive to saws, but to distinguish because they intergrade in color because this species is not a silica accumulator, and are very similar in anatomical structure. It the dulling effect can be attributed to the pinching is very possible that the wood reaching U.S. and resulting burning of the saw teeth as tension markets may be the product of two or three stresses are relieved in the lumber. Wood in this species. density class would require sharp knives to ensure The sapwood is white or yellowish-white and the production of smooth surfaces in planing. The wide; heartwood light to dark brown and fre- fine sawdust produced when machining the dry quently streaked with lighter and darker bands. wood is said to be responsible for allergic The grain may be straight but is more frequently responses in certain individuals. Responses noted interlocked to irregular. The texture is very have been sneezing and tearing. coarse but even. The wood weighs about 38 The wood is not durable under exterior con- pounds per cubic foot. ditions. It has been treated by the open-tank pro- The timber is stated to be a moderately re- cedure and absorptions of 5 pounds of creosote- fractory species with some tendency to end diesel fuel mixture were obtained in Malayan splitting and surface checking. tests. The heartwood is rated as moderately durable. Because this species has some degree of The presence of irregular and interlocked importance as an ornamental tree and in silvi- grain presents some difficulties in sawing and cultural practice, the lumber has been utilized planing, but in planing the problem can be on a relatively small scale and only for local alleviated by the use of proper cutting angles.

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