Science: Holey Smoke

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If, a year or so from now, skywriting airplanes fill the heavens over the U.S. with "Buy Nutsies" in mile-high letters of long-lasting, bright-colored smoke, the credit (such as it is) will go to Betty Lou Raskin. 36, a research associate at Baltimore's Johns Hopkins University. This week, at a Washington, D.C.. meeting of the American Society of Plastic Engineers, Miss Raskin unveiled the skywriters' dream weapon: "holey smoke" particles which are made of foam plastic and are so gossamer light that they hardly fall at all.

Most artificial smokes, Miss Raskin explained, are made of fairly heavy materials such as phosphorus pentoxide or petroleum oils. Even if their particles are only one micron (one twenty-five thousandth of an inch) in diameter, they fall through air at about eight inches per hour, which she considers too fast. Backed by the Air Force, Miss Raskin discovered a way to fluff various kinds of plastic into spherical particles that are mostly empty cells and almost as light as air. Miss Raskin's particles can be colored, and they fall 1,250 times slower than solid smoke particles of the same size. Collected in the form of a fine powder, eleven gallons of holey smoke particles weigh less than one pound.

Miss Raskin has sold the commercial rights to holey smoke to Dow Chemical Co. Besides skywriting, she sees a wide variety of potential uses for her discovery. Among them: 1) smokes to protect crops from frost; 2) military smokescreens and signals; 3) seeding rain clouds; 4) throwing up screens for the projection of movies (or advertising) on the sky.