MAKING THE MOST OF WOOD STRUCTURE AND ITS APPEAL TO THE EYE

As is well known, trees grow in diameter by the addition of new layers of wood, one of which forms just under the bark each year during the life of the tree. If growth is rapid, these layers, which are known as annual rings, will be relatively thick; if slow, they will be thin. In warm climates the growth of many trees is almost continuous, the fiber relatively uniform, and the annual rings very slightly marked. In cold climates growth is rapid in spring and summer, but almost ceases in winter, and the annual rings are sharply marked. The wood produced first in each year is frequently different from that produced later in the year, so that a distinction is drawn between the early springwood and the later summerwood. In such cases a cross section of the tree trunk will show a number of concentric annual rings whose number is equal to the age of the region of trunk cut. In certain kinds of trees, for instance, species of pines and leaf-shedding oaks, after the wood has attained a certain age, it darkens in color, so that when a crosscut of a 100-year-old part of the trunk is taken, the darker older central wood contrasts as heartwood with the surrounding pale sapwood.

All hardwoods contain a multitude of long continuous water-conducting tubes termed wood vessels; in cross section they are often visible to the naked eye as pores. In woods like oak and ash these pores are easily visible in cross section as minute holes, and in longitudinal section as fine grooves, which are often accentuated by furniture makers through treatment with a dark filler. In woods like maple and gum the pores are too small to be seen without a microscope.

Oak, chestnut, ash, and elm are conspicuous members of the ring-porous group of hardwoods, so called because one or more rows of large pores are formed at the beginning of each annual ring. Walnut and mahogany are diffuse-porous because the pores, though plainly visible, are more nearly uniform in size throughout the annual rings.

In addition to the annual rings and pores, traversing the wood at right angles to the fibers are thin stringlike structures that run from the outside of the wood radially inward toward the pith. In some woods these rays are too minute to play a part in the visible figure of the wood, while in others, notably the oak, they are conspicuous, and in quarter-sawed boards produce the effect known as silver grain or flake. These are the medullary rays. For more detailed information about wood structure, consult any reliable encyclopedia.

These variations in structure, plus variations in coloring, constitute the physical basis for the innumerable charming effects which expert wood workers are able to create for the furniture lover. Some of these effects can be produced in solid wood; others in veneer only. They result from four general methods of cutting:

Plain sawing, or cutting more or less with the grain at right angles to the rays.

Quarter-sawing, or cutting across the grain, parallel to the rays.

Transverse sawing, or cutting in a direction neither flat nor quarter, but between them.

Rotary slicing, in which the knife or the veneer lathe follows the lines of annual growth, but cuts across them irregularly to yield a striking effect of wavy lines and parabolas.

The interest of furniture buyers lies in the beauty, durability, romantic appeal and prestige value of the various woods, and not in the technical processes by which their individuality and fine qualities are brought out. However, a few facts concerning the various types of figures are here set down for possible emergency use.

VENEER AND PLYWOOD

Flat Slicing

Quarter Slicing

Half-Round Slicing

Rotary Slicing

Figure 17.—Slicing illustrated.

"The art of producing and using veneers dates back to the earliest days of civilization," says the Encyclopedia Britannica.[13]

Although we do not know when and where the art of veneering was invented, there is no doubt that it had reached a high development in Egypt 3,500 years ago. It was practiced by the ancient Babylonians and Assyrians, by the Greeks, and particularly by the Romans, who used it not only in furniture-making but also in door frames and panels. There is a record that Cicero, celebrated Roman orator, paid for a veneered table of citrus wood a sum equivalent to $20,000 in gold.

When the ancient European civilization gave way to the Dark Ages, the art of veneering was temporarily lost, only to be revived in the form of inlays during the Renaissance. True veneering did not become common in Europe until after the middle of the seventeenth century, when a new type of saw was invented which would divide a plank into thin sheets. As an early result of the discovery of the New World and the sea route to India and the East, many rare and exotic woods were carried to Spain, Holland, France, and England and used as veneers and inlays in the seventeenth and eighteenth centuries—among them mahogany, satinwood, amboyna, kingwood, rosewood, tulipwood, amaranth, harewood, and vermillion. The art of veneering reached the point of technical perfection during the reign of Louis XIV, and ever since that time it has been practiced by most of the great cabinetmakers in all countries; except of course, in the case of the carvers, of whom Chippendale is the outstanding example. Most of the magnificent furniture of France, that of the Hepplewhite, Sheraton, and Adam styles in England, and the really distinguished furniture of the late Colonial and Federal periods in America, made a free use of veneers.

The whole process of making veneers, from the selection of a tree in some far corner of the globe to the finished plywood, is a long and exacting one which demands the technical knowledge of scientists, engineers, and chemists as well as the taste of the artist.

Courtesy The Veneer Association

Figure 18.—Showing the construction of seven-ply plywood. The grain of each layer is at right angles to that of the adjacent ply.

Briefly, we can say that the logs must be transported, studied carefully in order to determine just how to secure the most beautiful effects from the wood, usually soaked or conditioned to soften the fiber, and sliced or sawed into sheets of veneer, which are afterward dried carefully. This is a work for specialists, and is usually done at established veneer mills. At the furniture factory the sheets must again be carefully studied, matched, clipped, taped, glued, and built under a pressure of 200 to 300 pounds into the finished plyboards.

A single tree may yield 500 board feet of lumber or the same number of surface feet 1 inch thick. Cut into thin face veneers this same tree would yield 10,000 square feet or 20 times as much in terms of surface area.[14]

ADVANTAGES OF PLYWOOD

Technically, plywood is the product resulting from three or more layers of veneers joined with glue, and usually laid with the grain of adjoining plies at right angles. Almost always an odd number of plies are used to secure balanced construction. The outside plies are called faces, or face and back. The center ply is called the core, and intervening plies, laid at right angles to the others, are called cross bands. Plywood is a device for combining lightness and great strength with freedom from the tendency to warp and split.

Modern engineering, chemistry, and machinery have brought the production of plywood to a point of perfection where it is as strong, weight for weight, as steel. It is wood engineered for beauty, strength, and economical application. Its peculiar excellence, as contrasted with solid wood, results from equalizing the normal internal stresses of the wood by running alternate layers in different directions. In standard five-ply construction, widely used for good furniture, the two outer and the middle ply, or core, have the grain running in the same direction, while the second and fourth plies, or cross bands, have the grain running at right angles to that of the others. Plywood was produced by the Chinese thousands of years ago, and is found in the furniture of the ancient Egyptians. Yet it has taken modern ingenuity plus engineering and chemical skill to develop a product capable of meeting the large scale but exacting requirements of today—a product now used on land, in the air, and on the seas. Plywood was not produced by machinery, and in commercial quantities, until about 50 years ago, when plywood factories were started in Russia. Ninety percent of all wood furniture manufactured today is of veneer and plywood construction. It is used in the interest of economy, strength, flatness, and beauty, not only in cabinet and furniture making but also in residence and office building, coach-building and various engineering industries, including aviation. Plywood offers maximum strength in all directions combined with minimum weight.

BOTH SOLID AND VENEER AVAILABLE IN WOOD FURNITURE

Some persons adamantly insist that to be truly good quality, furniture must be solid, built wholly of one wood. While many experts insist that this view is untenable, those who insist upon it should, of course, buy solid pieces. To do so will frequently involve denying themselves the full beauty of the fine graining which normally can be had only in veneer. The salesman and the industry should jointly educate the customer that good veneer is not only with us to stay, but is used in some of the best furniture made anywhere in the world and that good American veneer has lasting qualities in addition to its value in bringing to the average home graining and finish that can never be obtained in furniture made from solid wood.

SELLING VENEERS WITHIN PRICE RANGES

Courtesy American Walnut Manufacturers Association.

Figure 19.—Location of cuttings in tree body. Not every tree has a stump that can be cut into beautiful stumpwood. Fine crotches are much rarer and burls so precious that the choicest burl veneers, when mounted and matched for use in furniture, are worth more than their own weight in sterling silver. All other figure types are cut, by varying methods, from the long trunk.

The price range of veneer varies directly with the ready availability of the species, its color and figure, and its working and finishing qualities. Some veneers cost 20 times as much as others, and certain of the rarest and most beautifully figured sheets are literally worth their weight in silver. Well known commonly used species may be either high priced or inexpensive, depending upon the desirability and current demands for that figure.

To illustrate, American walnut may vary exceedingly in price. Taking the cost of the finest burl as 100 percent, crotch walnut might cost 57 percent as much; stump wood and figured long wood, 30 percent; and plain long wood approximately 5 percent. These percentages represent only the finest of each of these particular figures.

Therefore, instead of calling a suite "walnut" as if that is all there is to be said, it would be wise to point out that it is made of a particularly desirable piece of walnut, both rare and costly because of its fine figure and color. The same type of reasoning may be used in speaking of mahogany, maple, oak, and other beautifully figured cabinet woods.