Oobleck is a mixture of cornstarch and water mixed in a ratio of 2:1. Plan on at least ½ cup of cornstarch per child. So for one child mix ½ cup of cornstarch with approximately ¼ cup of water in a small bowl. It looks like a simple recipe, but oobleck is anything but simple- it’s a non-Newtonian fluid. That means it has properties of both solids and liquids. It’s crazy fun and a sensory delight!
How can you tell if you have the right mix? The contents of your bowl should react like a solid in response to pressure. Tap the surface hard and fast. Does it feel solid? If not, add a bit more cornstarch a sprinkle at a time and mix it up. Next, gently rest a finger on the surface of the oobleck. Does it sink down?
Oobleck is fascinating. Scoop up a handful and press it tightly in your fist to make a ball. After you’ve got a nice compact ball, relax and open your hand. Watch the ball melt away, dribbling through your fingers.
Toss a coin into the oobleck with some force and observe how it is slowly absorbed into the mixture. Now gently place the coin down and see what happens? What other factors affect interaction of the oobleck and the coins? Do you think each coin’s mass affects it journey down through the oobleck?
According to the US Mint, here’s the mass of common coins:
Maybe coin density plays a role?
Now that your coins are good and buried, give each little pirate a chance to fish out a coin one at a time until the all coins are gone. If you used different denominations, add up the coins to see who has the highest total. If you used one type of coin, a winner can be determined based on the year the coin was minted. Who has the oldest? The newest? Whose coin was pressed closest to their year of birth? There are many options for bringing numbers into the conversation
You can use small beads, buttons or coins as hidden treasure, too. These options open up a whole world of math as you ask the kids to assign values to the different sizes or shapes. Who wouldn’t value a shiny, plastic gem at $1,000,000?
Properly covered, the oobleck will stay fresh for a few days. Be sure to dispose of it in the trash, oobleck is bad for your plumbing, so don’t send it down the drain!
Photos courtesy of Kim Moldofsky