Simple Science: Magic Cornflour Mud, Oobleck, and Non-Newtonian Fluids

Borrowed another idea from G2’s class yesterday…

Magic Cornflour Mud

The recipe I borrowed from Scientific American:

• 1 1/2 cup cornstarch
• 1 cup cold water
• Food colouring

The intention was to make brown mud, but what d’ya know… I bought two bottles of blue food colouring instead of one blue and one yellow. Since I only had blue and red food colouring, we ended up with purple mud… The mixing process is kinda cool – the colours look awesome!

G2 had fun exploring the texture of his magic mud, better known scientifically as oobleck. Aside from all the fun you can get out of it, oobleck is also a great way to teach children about the properties of non-Newtonian fluids. Quicksand and silly putty are two other examples of non-Newtonian fluids.

Oobleck is a non-Newtonian fluid, which means that, unlike regular liquids, its properties are pressure-dependent. If you apply pressure, it increases its viscosity (thickness). A quick tap on the surface of Oobleck will make it feel hard, because it forces the cornstarch particles together. But dip your hand slowly into the mix, and see what happens—your fingers slide in as easily as through water. Moving slowly gives the cornstarch particles time to move out of the way. – Scientific American

It was fun for a while until G1 came along and complained about the smell. Something about the cornstarch mixture did not agree with his olfactory senses. Ever impressionable, G2 eventually agreed that it did not smell nice. Ah well… so we cleaned him up and whoops! We have a smurf! Guess our food colouring dose was a little too strong. It came off in the end though.

Here’s more about the science of oobleck from The Myth Busters – pretty cool “walking on water” stunt:

Related:

• Resources for Science Experiments
• More Simple Science Experiments you can do at home