Silly Putty Was a Wartime Attempt to Replace Rubber. It Failed at Everything Except Bouncing.

US2431878 covers a silicone-based bouncing putty developed during the Second World War, and it exists because of a genuine strategic emergency.

After Pearl Harbor, Japanese forces took control of the rubber-producing regions of Southeast Asia, cutting the Allies off from most of the world's natural rubber supply. Rubber was not a convenience; it was tires, boots, gaskets, hoses, and aircraft parts. The United States government poured funding into finding a synthetic replacement, and laboratories across the country went to work on it.

At General Electric's laboratory in New Haven, a chemist named James Wright, working on silicone chemistry, combined boric acid with silicone oil. The result was a substance nobody quite expected.

A material with contradictory manners

The putty is a non-Newtonian material, which means its behavior depends entirely on how fast you deform it.

Pull it slowly and it stretches like taffy, indefinitely. Yank it sharply and it snaps clean, like a brittle solid. Roll it into a ball and drop it and it bounces higher than rubber. Leave it sitting on a table and it slowly flows into a puddle, like a very thick liquid. Strike it with a hammer and it can shatter.

It also had a party trick that defined its early reputation: pressed onto newsprint, it lifts a mirror-image copy of the ink.

As a rubber substitute it was a complete failure. It could not hold a shape under load, it had no structural strength, and no one could find a serious industrial use for it. GE sent samples to engineers around the world asking for suggestions. Nobody had any.

Peter Hodgson

The putty circulated for several years as a laboratory curiosity and cocktail-party novelty. In 1949 a marketing consultant named Peter Hodgson saw it being passed around at a party in New Haven and recognized what everyone else had missed: the uselessness was the product. People could not stop playing with it.

He borrowed money, bought a batch, and packaged it in small plastic eggs — a decision made partly because Easter was approaching and partly because the eggs were cheap and the right size. He named it Silly Putty.

A New Yorker mention in 1950 produced a flood of orders. Silly Putty went on to sell in the hundreds of millions of units.

Where it ended up

Its afterlife is oddly distinguished. Apollo 8 astronauts reportedly carried it to secure tools in zero gravity. Physical therapists use it for hand-strength rehabilitation. Physics classrooms use it to demonstrate viscoelasticity, because there is no better five-second illustration that "solid" and "liquid" are not always distinct categories.

The wartime program that funded it did eventually produce real synthetic rubber, through entirely different chemistry. Silly Putty contributed nothing to the war effort at all — it is one of the most commercially successful research failures in American history.

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The full text of US2431878 is on patents.us.