May 10

What the heck is oobleck?

That is the first question that comes out of everybody’s mouth when you mention the word oobleck. The earliest use of the word “oobleck” that I am aware of comes from the title of a Dr. Seuss book. In the book by Dr. Seuss, Bartholomew and the Oobleck a king bored with ordinary rain, sunshine, fog, and snow causes green precipitation called Oobleck to fall from the sky. The Oobleck proves so sticky that it gums up the whole kingdom, which is eventually saved by Bartholomew Cubbins, the title character from Dr. Seuss’ 1938 book The 500 Hats of Bartholomew Cubbins. If you really want to learn more about oobleck, wikipedia goes into more detail about it is a dilatant fluids, polymers and psuedoplastics . . .

Oobleck is more commonly known among science teachers as the name for a substance made of cornstarch and water that has the peculiar ability to act like a liquid and solid at room temperature. Scientifically speaking, oobleck is a type of polymer. This means that it is made of very long chains of repeating molecules. Oobleck is also a non-Newtonian fluid, which means that its ability to flow changes when different amounts of pressure are applied to it. You can actually walk on it as long as you keep moving. More simply, if you squeeze oobleck, it will become brittle and crumble. If you just let it sit in your hand, it will drip and run like thin white school glue. Sound interesting? Try making some and explore it for yourself!

How to make Oobleck

  • 2 Cups Corn Starch
  • 1 Cup Water
  • 1 Quart-size Zipper Locking Bag
  • 1 Baking Pan (a small shallow Tupperware container works too)
  • Optionally you can also add a few drops of liquid food coloring to color your oobleck green, like in the Dr. Seuss book.
Procedure
  • Add the cornstarch to the zipper locking bag.
  • Slowly pour the water into the bag.
  • Gently knead the bag to mix the two substances. It should feel like thick pancake batter. Add more cornstarch if it is too thin or more water if it contains lumps of powdered cornstarch.
  • Add a few drops of food coloring if desired. Pour the substance out into your baking tray.
  • Poke your finger into the oobleck. What happens? Try to take a pinch of oobleck from the tray, squeezing your thumb and index finger as hard as you can. How does it feel? Pick up a handful of your amazing creation, let it drip from your fingers. Don’t be shy, explore what you can do with oobleck!
  • You can store your oobleck in the bag that you mixed it in, but unless you want to do a biology experiment, don’t keep it for more than 2 or 3 days!

Discussion

Following the procedure will show you some of the properties of oobleck, but the real science of any procedure is found by exploring further. Once you get a feel for the ideal consistency of oobleck, you can try making a really large batch of it (maintain an approximately 2:1 ratio of cornstarch to water) so that you have more to work with.

Here are a few ideas for further exploration:

  • Get several identical bowls and pour equal amounts of oobleck into each. What happens if you place objects of different masses on the oobleck. Do they sink? Float? Why?
  • The ratio of cornstarch to water given in the procedure is 2:1, but this is only an approximation. Start with 2 cups of cornstarch and incrementally add small amounts of water to it. How much water do you need to reach your ideal oobleck consistency? What is the new cornstarch to water ratio? What is the maximum amount of water you can add before the oobleck loses its interesting properties? What is this ratio of cornstarch to water?

What about Glurch?

Solution #1

a 3:4 mixture of white glue and water (e.g. 3/4 cup of white glue to one cup of water)

Solution #2

Saturated water/borax. Add enough borax that it won’t dissolve any more. This is approximately 3 tablespoons of Borax to 1 cup of water.

Directions

Add some food coloring (for effect only, not required to make the glurch work) to one of the two solutions then mix 3:1 of the first solution to the second. For example, 6 tablespoons of #1 to 2 tablespoons of #2. Stir together quickly or you may get an very dense blob in the middle. Stir/knead the glurch until it is of a uniform consistency. Or, since 3 tsp = 1 tbsp, use tablespoons to measure #1 and the same number of teaspoons to measure #2.

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