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Looking for an activity that is both fascinating and easy to make with the ingredients in your kitchen? Then Oobleck is the goo for you! It is basically just cornstarch and water, but at just the right mixture, it is a liquid while sitting still but turns into a solid the moment you squeeze it. Don’t believe me? Try it yourself! Also, Oobleck is easy to clean up. It rinses away from hands and clothes with water, or if you let it dry, it turns into a powder and can be brushed off. Just don’t pour a glob of it down your drain!

Recipe

• 1 cup of water
• 1 ½ – 2 cups of cornstarch
• food coloring

 Add food coloring to your water and slowly start adding the cornstarch. Start out with a cup and a half of cornstarch and continue to add more until the goo looks like a liquid, but the moment you try to stir, it cracks around the spoon and gets stiff. If it gets too stiff and turns completely into a solid, just add a little more water. Refrigerate Oobleck in a baggie if you are going to play with it more than one day.

 Now the real fun begins. Try poking it hard with your finger. What happened? Now try easing your finger into it. Did it react the same way? Put your hand in and try to pick some up. Can you roll it into a ball? What happens when you stop rolling it? Try pouring some from a cup, or put some in a tray and tilt. What do you notice? Try using a funnel. As the stream comes out the bottom, can you break it in two as if it were solid? Make another color of Oobleck and let the children mix the two. What other tools can you try with Oobleck? How do you think the Oobleck will react?

 The science behind it:

Cornstarch doesn’t dissolve in water like sugar or salt does. Instead, the tiny particles are suspended in the water, floating next to each other. When Oobleck is sitting still or gentle pressure is applied (such as easing your finger into it), the particles are able to move around each other and make way for things moving through it (like a liquid would act). When greater pressure is applied to Oobleck (such as poking it with your finger or squeezing it in your hand), the particles are forced closer together creating a “traffic jam”. When they don’t have space to move, the particles bunch up and behave like a solid. As soon as the pressure is released, the particles are free to move around again and will flow like a liquid.

Did you know?

Oobleck is used in games show challenges. If you had a swimming pool of Oobleck, you could run across it. Just don’t stand still!

What have you tried?

What are your Oobleck experiences or do you have other concoctions that you make with children? Share your ideas!