Oobleck (or also called goop) is an inexpensive and amazing sensory material. It’s a non-Newtonian fluid that has properties of both a solid and a liquid at once. This means that it looks like a simple bowl of liquid but if you apply pressure by hitting it with your hand, rapidly poking your finger into it, or trying to lift a submerged spoon out of the bowl it will freeze up and act like a solid. For the example of the spoon you can break off a section of the oobleck and lift it out of the bowl if you’re quick. If you stop applying the pressure and the oobleck relaxes it will act like a liquid. That spoonful of oobleck you just pulled out… it will drip off your spoon as it ‘melts’. If instead of poking the oobleck you instead rest your finger lightly on the surface of the oobleck it can slowly sink into it. If you’re apply the tiniest of pressure you can move your finger around. The fun comes when you try to pull out your finger. If you try your finger is either stuck or, if you pull hard enough, it ‘tears’ out of the oobleck and the oobleck that came out with your finger will drop back into the rapidly filling hole.

Materials Needed

• Cornstarch (one part)
• Water (1.5 to 2 parts) EDIT: I’ve since been making it with equal parts cornstarch and water.
• (optional) food dye for colored oobleck
• (optional) spoon, containers, and/or toys to use with the oobleck
• (handy) water and a towel available for washing

In the U.K. I’ve heard that there’s no cornstarch but you can make this with cornflour based on this Wired U.K. article the ratios are switched around.

Making oobleck is simple. To make it even easier you can leave some excess cornstarch out in case you add too much water. It’s basically 1 part cornstarch to 1.5 to 2 parts water. For instance if you use one cup of cornstarch you’ll want to add 1 1/2 to 2 cups of water. Lately I have some extra cornstarch set aside so I dump the amount I want to use in the bowl, add some water, and stir it. I try to add too little water so I can always add more. If you still have cornstarch in the mixture you’ll need more. If I add too much water and it becomes too soupy I can always add more cornstarch and I just end up with more oobleck.

If you want to dye your oobleck I’ve used food dye. If you wait until the end to add the dye it can be hard to stir the color into the oobleck, but you’ll end up with a really cool marbled look. If you want a solid color the best option is to add it to the water before adding it to the cornstarch so it get stirred equally throughout the oobleck.

If you’re allergic or don’t have any cornstarch you could use another starch. I haven’t tried anything other than cornstarch, but Create in the Chaos created a corn-free oobleck with arrowroot starch flour so it would be interesting to see what other cornstarch substitutes (epicurious link) might work.

Play

Basically fill a large container with oobleck and let them play. I supplied a couple cheap spoons for mixing and dribbling while Ada was quick to grab the dinosaurs.

Cleaning

Any oobleck left out for too long will basically turn back into cornstarch. Since it’s just starch and water you can easily add more water to your bin of oobleck turning it into a slurry that can be washed away. Ada’s favorite activity is playing with it and then peeling off all the dried oobleck on her hands and arms so I normally have the kids play with oobleck outside on the deck or (mostly) contained in their sensory bins at the kitchen table.

Here the kids added a lot of water to the container of oobleck which created a slurry. If they had mixed it together it might have emptied the container quicker when Zoey dumped it. As it was if you were cleaning this in the kitchen just add water, mix, dump, and repeat until cleaned out. In this case I ended up with white all over my deck after this activity (until more kid sensory play or rain happens to clean it off).

Inside Play

If you’d prefer to contain the play a bit more you can split it up amongst the kids and have them play at the table in their sensory bins. Cleaning is easy as it’s just a quick wipe or two of the floor or you can vacuum it up later after any leftovers are dried up.

I frequently extend the play and get them to clean up their toys themselves by switching out the oobleck for water. They can decide if they want bubbles (dish soap) or not. If they spill enough water it’s a simple towel wipe of the table and then the floor. Part of the play can also include drying their toys off afterwards. If they’re not interested you could always tell them they’re doctoring their toys (Ada has come up with cleaning her toys’ dusty musties before).

Extending the play some more

If you want to extend this even further, oobleck is really cool when placed over a subwoofer. I’ve never tried this but have watched videos before. If you want to see more you can start with The Kid Should See This: Oobleck (non-Newtonian fluid) on a subwoofer or Fatherly: Blow Their Minds With Just Cornstarch, Water And A Speaker.

If you had enough cornstarch and water you could even walk on it. There’s a lot of videos floating around of people walking on it, but I’ll link to IFLScience’s post. I’m just glad I don’t have to clean up a pool of oobleck.

I hope this helps you create a fun and simple sensory activity for your child. This is cool enough to keep them occupied on their own, make you want to play with it, and is perfect for a larger gathering too. I love how this simple and quick to prepare activity can entertain and all I need to keep on hand is an extra container or two of cornstarch in my pantry.

I’d love to hear whether you made up a batch of oobleck and how you customized it. Feel free to reach out through the comments below, on my Facebook page, or through Instagram. Hope you have a great day!