AMERICAN HARDWOODS

For the information of consumers of hardwood plywood the following brief descriptions of most American hardwoods used for plywood are supplied.5

American Walnut.

This native hardwood is often referred to as "the cabinetmaker's wood." The ease with which it lends itself to the tools of the wood craftsman, its combination of aesthetic and physical properties, and

its enduring qualities were early recognized. When the colonists first settled America, walnut abounded throughout the eastern half of the country and grew on much of the land needed for farming. In the process of clearing the land the value of walnut became readily apparent to the pioneers, and it was accordingly used in building and equipping their homes. Many pieces of walnut furniture as well as floors and interior trim were found on the premises of the early settlers.

Walnut is still one of the most loved of our native hardwoods and outranks all other domestic hardwoods in the production of face veneers. Ranging in natural color from the creamy white of the sapwood to the mellowed browns of the heartwood, walnut lends

5 More detailed information on these and additional species is available in American Hardwoods and Their Uses, published by the Bureau of Foreign and Domestic Commerce as Trade Promotion Series No. 178 (available from the Superintendent of Documents, Washington, D. C.; price, 15 cents). For technical data on the physical and mechanical properties of wood, refer to Wood Handbook, Forest Products Laboratory, Madison, Wis. (available from Superintendent of Documents; price, 25 cents).

itself to the lovely finishing effects decreed by modern stylists. Almost every type of figure known to veneer cutting is found in walnut. Its trunk, burls, crotches, and stumps yield some of the most attractive wood grains to be found in the world.

Figure 5.-This pictorial scene, created from selected wood veneers, is an exceptional illustration of the potentialities offered by the wide variety of color and figure in hardwood. In addition to its aesthetic feature, walnut is also outstanding in mechanical and strength properties. It is hard, heavy, strong, and

Results of tests to measure the properties of structural cabinet woods conducted by the Forest Products Laboratory at Madison, Wis., are graphically pictured in a leaflet, The Story of American Walnut, available on request to American Walnut Manufactures Association, Chicago. Most of the data resulting from tests are also published in Bulletin No. 556 and Technical Bulletins Nos. 158 and 479 of the U. S. Department of Agriculture (available from Superintendent of Documents, Washington, D. C.).

stiff. It has good shock-resisting ability; can be satisfactorily kilndried or air-dried; takes finishes and stains; takes and holds paints exceptionally well; and can be readily polished. It_glues well and shrinks or swells very little after being seasoned. In resistance to decay the heartwood of walnut ranks with the most durable woods. Red Gum.

One of the hardwoods most widely used for plywood is red gum. The sapwood is commonly called "sap gum." Red gum with unusually rich, variable coloring and irregular markings is known as "figured red gum.'

The beautiful coloring and handsome grain of red gum have made it especially desirable as a paneling wood. The heartwood of red gum is reddish brown with occasional dark streaks. As seen from the end of the log, the heartwood may make a star-shaped pattern against the almost white color of the sapwood. Such logs, or logs of similar nature, when properly cut will produce the unique designs of "figured red gum.'

"Sap gum" cut from the sapwood of red gum is almost white and, except for lack of color, has practically the same properties as heartwood. It is easily stained to match the heartwood, but for most decorative purposes the latter is more desirable.

Red gum has an interlocked grain-which means that the elements or wood fibers are not constant in one general direction, but cross and recross. The reflection of light on the alternate areas of interlocked grain, in which the fiber direction is opposite in the adjacent strips, is believed to account for the "ribbon" or "striped" effects obtained from quarter-cut flitches. In this type, alternate light and dark strips run longitudinally to the board.

Red gum is moderately heavy and moderately strong. The wood is even textured and is well adapted to veneer cutting by any of the three processes: slicing, rotary cutting, or sawing. It takes stain, paint, and glue well.

Oak.

No American hardwood has greater renown than oak. Found in every section of the United States where hardwoods grow, oak has played an important part in the development of the country from its earliest history. Its uses are legion-from railroad ties and ship timbers to fine furniture and wall panels-exemplifying its great strength, durability, and attractive appearance.

Oak is divided into two groups, red and white. Of the many species comprising these groups, 20 are of commercial importance. True white oak (Quercus alba) is the most important of all oaks, and true red oak (Quercus borealis) the most important of the redoak group. These two species are the ones principally used in manufacture of plywood and veneers.

Both the red and the white oaks are ring-porous-that is, the pores in the springwood are large and conspicuous in comparison with the pores in the summerwood. The decrease in size of the pores from springwood to summerwood is abrupt, thus forming distinct rings of large and small pores. Also, all species of red and of white oak groups have large medullary rays. The combination of the large rays and conspicuous summerwood pores accounts for the figure in oak. The flaked appearance of some oak veneer is due to the ex

posure of the flat surfaces of the wood rays by quarter cutting. The variation in summerwood and springwood pores, however, is more conspicuous in plain or flat cutting.

Oaks are generally heavy, hard, stiff, and strong, with good shockresisting ability. Their wear-resisting qualities and beauty of grain account for their extensive use. Tests indicate that red oaks and white oaks are about equal in general strength properties. The heartwood of the red oaks is generally brown with a tinge of red, and that of the white oaks grayish brown with no reddish tinge.

Yellow Birch.

Among the important American hardwoods used in plywood manufacture yellow birch ranks high. Possessing a distinctive and pleasing variety of figure in sawn, rotary-cut, or sliced faces, birch plywood offers ample latitude for broad architectural and decorative expression. "Curly" birch exhibits a wavy figure of changing high lights and shadows. The sapwood is of light color and the heartwood is brown with reddish tinge.

Yellow birch is heavy, hard, stiff, and strong, with high shockresisting ability. The wood is compact, uniform in texture, and capable of taking a high polish.

Hard Maple.

There are 13 species of maple growing in the United States, 6 of which are of commercial importance. They are divided into two groups, hard maple and soft maple. The hard-maple group is composed largely of sugar maple and black maple. Its light color and its enduring properties have brought maple to a position of prominence in the hardwood-plywood industry. The wood is of uniform texture, is heavy, strong, and hard, and takes an excellent finish. Certain logs produce "curly," "bird's-eye," and "blistered" figures. Yellow Poplar.

The use of yellow poplar in the manufacture of hardwood plywood finds its greatest importance as core stock, cross-banding, or utility veneers. For this latter purpose, yellow poplar takes second place among all native hardwoods, although at the same time it holds sixth place in production of face veneers. Yellow poplar works easily and has a remarkable affinity for glue. These characteristics make it particularly suitable for cores and cross-bandings. It is lightweight, soft, moderately strong, straight grained, and of uniform texture, and takes paint exceedingly well. The sapwood is white and the heartwood greenish yellow.

Tupelo.

Because of the similarity of tupelo to gum in many respects, especially in texture and appearance, this wood is many times referred to as "tupelo gum," although technically it belongs to an entirely different genus and family. Like gum, it has interlocked grain producing a similar "ribbon" or "striped" effect from quarter-cut flitches, especially desirable for decorative purposes.

The sapwood is almost white, usually with a gradual transition to the light brown of the heartwood. Tupelo is fine grained, is of moderate strength and stiffness, and, owing to its interlocked grain, is difficult to split.