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SciTech Tuesday: Silly Putty is a WWII invention

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In 1943 James Wright, a Scottish-born engineer working for General Electric mixed silicon lubricant with boric acid. It was too sticky to be the artificial rubber he wanted, but when he dropped it it bounced. It was interesting enough for a patent application. Engineers with Dow Corning filed a very similar patent slightly later.

The product of the patent was developed into a toy, called Silly Putty, in 1949. Today about 6 million eggs of Silly Putty a year are sold by Crayola, who purchased the rights to sell Silly Putty in 1977. Silly Putty is a non-newtonian fluid–this means that it has characteristics unusual for a liquid or a solid. If left in a shape it will eventually flow to a flat shape like a liquid. However it bounces, and when struck strongly and sharply will shatter.

Because it is made of silicon lubricant, if your Silly Putty gets stuck on a pourous surface (like hair or fabric) you can dissolve it with WD-40 or alcohol.

At home you can make a substance with very similar properties. You’ll need Borax (which you can find at the grocery store next to the bleach) and white glue. White glue is a polymer (polyvinyl acetate, or PVA) like silicon lubricant. The Borax affects the glue like the boric acid Wright used changed the silicon. Here’s a recipe we use in our Real World Science curriculum:

1/2 cup white glue

3/4 cup water

1 tsp borax

Dissolve the borax in the water, and then mix it with the glue. Put the resulting polymer into a ziploc bag and knead it until it forms a nice stretchy mass. Pour remaining liquid down the drain.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum.

image from The Museum of Play

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