Toying With a Ridiculous Material
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Toying With a Ridiculous Material The shortage of natural rubber during the Second World War prompted research for alternatives. Substituting silicon for carbon—the backbone of natural rubber chains—quickly became a major line of investigation, but it would take years of research to produce usable silicone rubber materials. Along the way, groups at both the Mellon Institute in Pittsburgh, Pennsylvania (through a fellowship sponsored by Dow Corning) and General Electric in New Haven, Connecticut, accidentally stumbled across a novel material that has fascinated generations of children and adults and started perhaps the silliest debate in the history of science: Who invented Silly Putty? The official line is that in 1943 James Wright, an engineer working in General Electric’s New Haven laboratories, accidentally put a drop of boric acid into silicone oil, and found that the resultant gooey material bounced when he threw it on the floor. It also stretched more than natural rubber. After experimenting with various compositions, Wright applied for a patent on a “Process for Making Puttylike Elastic Plastic, Siloxane Derivative Composition Containing Zinc Hydroxide” on December 23, 1944; he was awarded U.S. Patent Number 2,541,851 on February 13, 1951. However, Earl L. Warrick and Rob Roy McGregor at Mellon Institute, working for Dow Corning, may have a better claim to the invention. They were experimenting with ways to make polydimethylsiloxane (PDMS) fluids more viscous. At some point, they, too, added boric acid to the mix, with the same results. As Warrick recalled in his memoir Forty Years of Firsts: The Recollections of a Dow Corning Pioneer, “By late summer 1940 we knew how to carry fluids to a ‘gummy’ or rubbery state, but we still had not developed a silicone rubber. One of our attempts produced instead a curiously resilient material which we called ‘bouncing putty.’ We knew the substance was not the polymer we were looking for, but we added fillers to it and took advantage of its unique properties to astound visitors by bouncing it off the ceilings and walls of our laboratories.” They applied for a patent on March 30, 1943, for “Treating Dimethyl Silicone Polymer with Boric Oxide,” and were awarded U.S. Patent Number 2,431,878 on December 2, 1947. So, if Warrick’s memory is correct, he and McGregor invented bouncing putty three years
before Wright. The patent filing and award dates favor them, also. Whether either group knew what the other had created is not known, but it made little difference because “no use was apparent at the time,” as Warrick wrote. What is not in dispute is that a unique material had been born. According to the official Web site (www.sillyputty.com), it has many interesting properties: “It stretches without breaking, yet it can be ‘snapped off’ cleanly. It bounces higher than a rubber ball. It floats if you shape it in a certain way, yet sinks in others. It can pick up pencil marks from pages and comics from some newspapers. If you slam it with a hammer, it keeps its shape, yet if you pu
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