"Improbable Sandwich"

Weight for weight, the strongest structural material in the world is not steel or any other metal but "an improbable sandwich"--two or more thin sheets of wood pressed together with glue between. This is plywood. In an article describing plywood and its modern technology, FORTUNE last week declared that new plywoods are as different from old "as a 1940 automobile from a vintage of 1910." Plywood is at least as old as 1900 B. C.--for a mummy case dated thereabouts, and discovered in Egypt, was made of it. But until recently the only glues available were starch glue from tapioca, blood albumin glue from slaughtered cattle and other animal glues. None of these was an adhesive that would "really stand up and fight with tension, torsion, or shear."

Better glues were made from casein, a protein ingredient of milk, and from soybeans. In 1912 Dr. Leo Hendrik Baekeland, father of plastics, took out a patent on a synthetic resin for plywood filler, but did not start to exploit it until 1932. In 1926 a German chemist, Dr. T. E. Goldschmidt, developed a filler made of tissue paper impregnated with phenolic resin. This made a bond so firm that the sandwich was stronger weight for weight than steel. It was also waterproof and bacteria-proof.

The new plywood technology did not get under way in the U. S. until 1930 and is just now beginning to grow rapidly. Figures for 1937 (latest available) put total U. S. plywood production at $45,500,000. The figure for 1939 will probably be around $80,000,000. The stuff is being used for luggage, piano cases, radio cabinets, speedboats, concrete forms, truck bodies, prefabricated houses, cinema studio sets, boxcars, beer barrels, showcases, jigsaw puzzles, Ping-pong tables. Eugene Vidal, onetime head of the U. S. Bureau of Air Commerce, is now president of a small company which has developed a low-cost plywood airplane, and he plans soon to lease manufacturing rights. FORTUNE estimates the total number of plywood uses, decorative and structural, at more than 2,000.

Plywood is made by putting a big log into a peeling machine, which strips off the thin wood sheets like wrapping paper from a roll. When the sheets are cut to size, the sandwiches are made in presses which deliver squeezes up to 200 Ib. per sq. in. The San Francisco World's Fair, which accounted for 10,000,000 sq. ft. of fir plywood, used plywood 29 layers thick for parts of its Colonnade of States.

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