Is it a solid? Is it a liquid? It’s both! Making your own oobleck is an easy, cheap, rainy day science activity that only requires a couple of everyday kitchen ingredients and is sure to fascinate kids and adults alike.
Oobleck sounds complicated, but it’s not. It gets its unusual name from a Dr Seuss story, but really, it’s one of the simplest science activities you can do with your children and they will be enthralled by the way it can be both solid and liquid (sometimes referred to as a ‘non-Newtonian fluid’ because it does not follow Isaac Newton’s observations on how liquids behave).
What is oobleck?
How does oobleck work? It’s all to do with the particle size and how these interact with water. Cornflour (known as cornstarch in the US) has a very small, fine texture and when mixed with water, the starch particles suspend rather than dissolve. When oobleck is still or stirred slowly, the water surrounding each starch particle allows the mixture to flow smoothly.
However, when pressure is suddenly added – such as the surface of the oobleck being struck by a spoon or the mixture being squeezed – the starch particles compress together, temporarily pushing the water out of the suspension and making the mixture behave like a solid. Try getting kids to tap their fingers over the surface, then let their finger slowly sink into the mixture to see the difference.
Making our oobleck recipe only requires cornflour and water. You can add food colouring if you like, but it’s not essential, so don’t worry if there’s none in your pantry.
Oobleck is technically edible, but it won’t taste good! It’s safe for children of all ages to play with and is a great introduction to the world of slime-making. If your children love playing with oobleck, they might also really enjoy squishing our homemade playdough.
Easy oobleck recipe
Makes 1 small quantity for a child
Prep 5 mins
- 75g cornflour
- 50-60ml cold water
- Tip the cornflour into a bowl and slowly stir in the water.
- If the mixture seems too dry, add a few drops more water. If it’s too liquid, add some more cornflour. The oobleck is ready when the mixture is thick and fluid, but starts to tear if stirred fast.
- The oobleck can dry out as you play with it. If this happens, simply add a few drops of water to loosen it.
Top tips for making oobleck
Oobleck is messy – either play with it outdoors or somewhere that can be easily cleaned (like the kitchen). Roll-up your sleeves and wear aprons.
If you want coloured oobleck, add a few drops of food colouring to the water first, as it will be very difficult to stir it in later.
If your oobleck doesn’t turn solid, stir in ½ tsp cornflour at a time until you get the consistency you want.
Oobleck lasts for a couple of days – just add a little water to the mixture to reactivate it. It can pick up fluff and dirt, so we wouldn’t recommend using it beyond this time or playing with it if it’s become grimy.
To clean up after playing with oobleck, you can use another piece of oobleck to quickly gather up smaller puddles/clumps. Wipe off hands and equipment with kitchen paper, then run under clean water. A damp cloth will clean up any surfaces. To dispose of oobleck, leave it open on the counter overnight, then scrape the dried mixture into the bin.
Kids’ crafts and cooking projects
Have you tried making oobleck? What did you notice?