It’s an undisputed fact that children gravitate towards anything egg shaped:
Tomagatchi. Cadbury crème eggs. Weebles. But perhaps the most exciting egg you could open as a child was one of these babies:
Oh yeah.
We’re talking about silly putty.
You can stretch it, mold it, tear it, bounce it. You could press it against the Sunday Funnies and pull up a (backwards) copy. You could grind it up into the carpet and cause your mother great amounts of distress. You could probably even eat it, though that’s not recommended.
But what is it?
Part of what makes Silly Putty so mindboggling is its ambiguous state of matter. It seems too liquid-y to count as a solid, but to solid to count as a liquid. Turns out, it’s a “viscoelastic liquid” which means it’s a viscous liquid, but it has some properties of an elastic solid. Viscoelastic liquids are a type of non-newtonian fluid. It’s categorized as such because its viscosity increases with increased stress. Viscosity is just a fancy word that refers to how “flowy” a liquid is. High viscosity means it doesn’t flow as easily. Water, for instance, has very low viscosity. Viscosity is measured in pascal seconds.
What’s it made of?
Like most great things, Silly Putty was the result of a serendipitous mishap. A GE engineer accidentally dropped some boric acid into silicone oil, stumbling into one of the worlds most amusing substances. It’s mostly made up of polydimethylsiloxane (PDMS). PDMS is a siliconepolymer, and everyone knows polymers are basically the most fun materials in the universe. A polymer is made up of a number of repeated subunits called monomers.
How does it work?
The hydrogen bonds between the molecules are fairly weak and can be broken under stress. With minimal stress, only a few are broken, which leads to the long, stringy, stretchy look. If you’ve ever tried to tear silly putty quickly, though, you’ll notice that it forms a clean rip. This is because higher stress will break all the bonds, and you’re left with two pieces.
I want some right now. Can I make some right now?
Sure! You’ll need some Elmer’s glue, some Borax, some water, and, if you don’t want your putty to be really lame, some food coloring. Then:
-Empty the glue bottle into a bowl
-Fill the now mostly empty glue bottle with warm water, shake, and dump that into the bowl
-Add some color
-In a cup, mix 1 tsp borax powder with ½ cup warm water
-Slowly mix the borax mixture into the glue mixture. Eventually you’ll need to knead it.
BAM! You’ve got yourself some putty, buddy.
See, the borax makes the polymer chains in the glue link up with one another in a process called cross-linking. This makes a large web-like structure of polymers, giving it the consistency of a putty.
But the kind you buy at the store will probably be better. Not least because of the egg thing.
That’s all for now,
Dr. Mollie Cule
Sources:
http://chemistry.about.com/od/everydaychemistry/a/sillyputty.htm
http://people.howstuffworks.com/silly-putty4.htm
Wikipedia
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