Non-Newtonian Cornstarch Recipe
Mixing cornstarch and water produces an amazing, non-Newtonian goo that's perfect for science play.
When you make this amazing ooey, gooey gloop, you’re guaranteed to hear squeals and “ooohs & ahhhs” coming from everyone playing with it! Using only cornstarch and water, this amazing mixture behaves like a solid one instant and a liquid the next. A little bit of pressure changes everything! By the end of the experience, you’ll have your hands on, in, and all over this wonderful solid-liquid (or is it a liquid-solid?) goo.
//Compose the Material Product list items ?>
- Cornstarch, 1 lb (454g)
- Large mixing bowl
- Baking sheet or tray with sides
- Large spoon
- Large-size zipper-lock bag
- Newspaper or a plastic drop cloth to cover everything
- Water and paper towels
- Food coloring (optional)
- Adult supervision
NOTE: Anyone working in the bowl needs to wash hands first. That keeps the goo much cleaner and more pleasant to study.
Pour the box of cornstarch into the mixing bowl and add one cup (237ml) of water. It’ll be tough to stir with a spoon. It’s just easier – and way more fun – to mix the cornstarch and water with clean, bare hands.
(Using colored water is an option. Just keep in mind that stained hands and clothes and floors may become a concern even with everything covered with a drop cloth.)
Continue adding water (and/or cornstarch if needed) in small amounts until you get a mixture that has a consistency similar to honey. It may take a little work to get it just right the first few times, but you’ll eventually end up mixing one box of cornstarch with 1 to 2 cups (237 to 473ml) of water. The nice thing about it is that you can’t make a mistake – but it sure is fun!.
Pour the mixture onto a tray, cookie sheet, or baking pan. Notice its unusual consistency as you pour it. Stir it on the tray with your fingers, first very slowly and then, as fast as you can. You may be surprised at what happens. Skim your fingers across the top of the glop. What do you notice?
Gather a handful of the glop and lift it off the tray. Roll the goo between your hands and make a ball. Hand the ball to someone and watch what happens to the ball.
Hold your hand flat over the pan palm-down and smack the liquid glop as hard as you can. Most helpers will duck for cover as you get ready to slap the liquid because they expect it will splash everywhere. Surprise! All of the glop stays in the pan… hopefully. (If a little mixture inadvertently splatters, clean it up, toss it into the trash, and add a bit more cornstarch to the batch.)
Smack the glop in the tray again but this time, lift your hand straight up from the table. Surprise – again! The tray and the glop come up off of the table with your hand. However, it will quickly fall back to the table so don’t go too high.
As you play with the glop, speculate as to why the “liquid” behaves as it does. What causes it to feel like something solid when it’s squeezed, yet flow like syrup when the pressure is released? When you’re finished with the activity, pour the glop into a large zipper-lock plastic bag to store it for later use. (Mixing and “researching” it with clean hands helps it store longer.)
How Does It Work
This goo is an example of what’s called a non-Newtonian fluid – a fluid that ignores Sir Isaac Newton’s Law of Viscosity. All fluids have a property known as viscosity which is the measurable “gooeyness” of the fluid or its resistance to flowing. Honey and ketchup are liquids that have a high viscosity or resistance to flowing. Water has a low viscosity.
Newton stated that the viscosity of a fluid can be changed only by altering the fluid’s temperature. For example, honey flows easily (low viscosity) when you warm it but becomes very thick (highly viscous) when it gets cold. A non-Newtonian fluid doesn’t have the same dependence on temperature because its viscosity changes when stress or a force, not heat, is applied. When you squeeze a handful of the glop you made, the particles of cornstarch come closer together and trap the water between them. Its viscosity increases and it acts like a solid… for a split second. When you release the pressure, water fills the spaces between cornstarch particles again and the glop behaves like a liquid.
Take It Further
Not surprisingly, when you get a handle on the perfect consistency, there are several cool activities that use the glop for research. See where your creative science-mind will take you! Check out these Spangler Science links:
- Cornstarch Science – Quicksand Goo This includes instruction by Steve and Jack Spangler, an explanation of quicksand, and how to mix 2500 pounds (1134k) of cornstarch goo in a cement mixer truck.
- Cornstarch Monsters – Science Fair Project, Sick Science #055 Cornstarch goo takes on some strange shapes when sound waves are applied in a controlled way. Project variables are suggested.
- Cornstarch Monsters – Science Fair Project by Jack Spangler Jack shares the details of a science fair project he submitted. Even if his subject isn’t of interest to you, this is a great one watch to discover the thought process and steps involved in a winning project.
- Electric Cornstarch, Sick Science #194 Static electricity and your non-Newtonian fluid combine for an amazing, hands-on, non-water based activity.
If you’d like to dig a little, the original cornstarch glop was discovered in 1949 by a young researcher named Bartholomew. A writer named Dr. Seuss tells his story in a book titled Bartholomew and the Oobleck. You might as well get the historical facts about the goo you made.
Strangely, the mixture will not stay mixed indefinitely. Over time, the grains of cornstarch will separate from the water, sink, and form a solid clump at the bottom of the bag. It’s for this reason that you must not pour the mixture down the drain even with adding lots of water. The mixture will settle in pipe traps, harden, and clog the pipes completely! Keep the mixture in a zipper-lock bag and simply toss it into the trash when you’re finished with it.