When non-Newtonian fluid meets a 60 Hz sine wave pumped through a 15-inch speaker, colorful monsters come to life.
Halloween is our favorite time of year! Being the mad scientists that we are, we couldn’t pass up the opportunity to bring some colorful monsters to life with a little bit of science. This is a fun DIY experiment that you can do at home! If you’re looking for an amazing Halloween science demonstration, or simply want to experiment in your own secret laboratory, we highly recommend using a black light. Steve Spangler’s Oobleck will create the most colorful monsters that appear to emit a spooky radioactive glow under black light.
- Sound Source (audio device, or tone generator)
- Shower Curtain (plastic bag or sheet)
- Steve Spangler's Oobleck powder
- Black Light
- Mixing bowl or container
Find a speaker.
Our speaker came out squeaky-clean and without any damage at all. However, it’s possible that your speaker could wind up a bit messy and possibly damaged. Select a speaker that is easy to clean up, and/or an old speaker that you are not afraid of damaging. Any size speaker will work. In our example, we used a self-powered 15-inch speaker.
Remove the grill or screen.
In order for this experiment to work, you will need direct access to the speaker cone. Depending on the speaker, you may need to unscrew a metal grill or remove a cloth screen from the face of the speaker.
Lay the speaker on its back and cover with plastic.
In the past, we have found great success with a double layer of plastic wrap. Plastic wrap will work great for smaller profile speakers. In our example, we needed to cover more surface area than plastic wrap could cover. We opted to use a clear shower curtain that was trimmed down to size with scissors.
Make sure speaker ports have room to breathe.
Some speakers have one or more ports located on the front, sides, or back of the speaker cabinet. These ports allow air to move in and out of the speaker cabinet. The airflow is restricted when these ports are blocked–limiting the distance the speaker cone can travel while vibrating. In other words, you need air movement to have speaker movement–especially with lower frequencies.
In this example, we added a block under the shower curtain to create space for air to flow in and out of those ports underneath the curtain.
Select your favorite color of Steve Spangler’s Oobleck powder.
Steve Spangler created a special mixture of powders that replicate quicksand. The texture will blow your mind. Simply adding water turns the powder into a goo that can be both a liquid and a solid. Scientists call this type of substance “non-Newtonian” because it doesn’t follow Newton’s laws. Sir Isaac Newton would have been so confused. Due to an exclusive pigment used in Steve Spangler’s Oobleck, it even glows under black light.
*Note: You can substitute Oobleck powder with cornstarch powder. Be advised that cornstarch powder will not react with the same glowing effect under black light.
Add water and mix.
Pour the 16 oz bag of Oobleck into a large mixing bowl or container. Add 1.5 cups of water. For the full sensory experience, we recommend using your hands to mix–the feeling is incredible. You have reached the desired consistency when you can roll the fluid into a ball in your hands, and watch it turn back into a liquid that drips through your fingers when you stop applying force.
Pour Oobleck into the center of the speaker cone.
You will need to experiment in order to find the ideal volume of Oobleck that is right for your speaker. Generally, larger speakers can handle larger amounts of Oobleck. In our example, we noticed the best response when using 8 oz to 10 oz.
Though it is possible to create Oobleck Monsters with any bass heavy music track, we recommend using a tone generator for more control over the consistency and intensity of your Oobleck Monsters. There are many free apps available for your smartphone or tablet. Look for a tone generator app that allows you to select frequency and volume.
You will need to experiment with different frequencies and volume levels to create the best monster performance from your speaker. In our example, we used a smartphone app dialed in at 60 Hz and at varying volume levels for effect.
Note: For your comfort and hearing protection throughout this experiment, we recommend using earplugs or the good old-fashioned fingers in your ears technique.
Troubleshooting: If the pool of Oobleck only appears to ripple and will not come to life, you may need to remove some of the Oobleck from the speaker cone, turn up the volume, or select a different frequency.
Turn on your black light.
Oobleck offers an incredible radioactive-like experience under black light.
Add multiple colors.
Oobleck comes in varying colors. Experiment with different colors and watch them blend with each other under black light.
How Does It Work
Oobleck is a non-Newtonian fluid. This means it doesn’t necessarily follow Sir Isaac Newton’s law of viscosity. When force is applied to the fluid, it behaves like a solid. When little or no force is applied to the fluid, it behaves like a liquid. You can experience these differences in states of matter in a few different ways. Here are some of our favorites:
- Fill a mixing bowl with Oobleck and punch the fluid. Did it appear to behave like a solid? What happens when you slowly push your hand into the mixing bowl? Does it behave like a liquid?
- Fill a cup with Oobleck and poke your finger quickly into the fluid. Were you able to reach the bottom? What happens when you poke your finger very slowly into the fluid? Can you reach the bottom now?
- Grab a handful of Oobleck and try to roll it into a solid ball in your hand. When you stop applying force, what happens? Does it drip through your fingers like a liquid?
When you apply force to the fluid, you force the long starch molecules of Oobleck closer together. The impact of this force traps the water between the starch chains to form a semirigid structure. When the pressure is released, the Oobleck flows again.
Is sound creating the monsters?
Though sound is involved in this experiment, it’s actually not the sound that animates the Oobleck fluid into monster-like shapes. In this case, the speaker itself creates the monsters as it forcefully pushes the fluid up as it vibrates. Just like the example above, when you hit the Oobleck with your fist, the fluid behaves like a solid when direct force is applied. In this case, the fluid moves outward and stacks upon itself in an ever-evolving fashion.
Why do lower sounds work better?
Lower sounds, or lower frequencies, produce longer waveforms. Higher sounds, or higher frequencies, produce shorter waveforms. This means that a single wave at a lower frequency travels a longer distance. As the speaker vibrates, it moves in and out (or up and down when laying on it’s back). The Oobleck Monsters experiment will work better at lower frequencies because the speaker can apply force across a longer distance as it moves up under the pool of Oobleck fluid. This allows for more of the Oobleck molecules to stack on each other before the speaker moves back down, and the cycle repeats.
In other words, the force is greater when the material of the speaker cone vibrates at lower frequencies because the force is applied over a longer period of time and over a longer distance. It’s like punching the Oobleck from underneath, over and over again.
Take It Further
Get it on video.
If you decide to film your experiment, you may find that your video footage looks out of focus once the sound kicks in. Believe it or not, there’s a scientific explanation for that.
If you’ve ever filmed a car and noticed the wheels on the car spinning backwards, then you may have an idea of what’s going on here. The vibration of the speaker is out of sync with the frame rate of your camera–that’s the amount of times the speaker moves up and down compared to the number of images captured per second by your camera.
In our example, we had to increase the frame rate of our camera from 30 fps to 60 fps, and it was still a little blurry. However, some smartphones can go up to 120 fps or 240 fps. A higher frame rate will allow you to capture more images per second, essentially capturing more snapshots of the motion of the speaker, resulting in smoother and clearer motion in your video footage.
Science Fair Connection
Follow your Science Fair Instruction Guide, and try experimenting with some of these variables:
- How do Oobleck Monsters react to different frequencies?
- Lows – 20 to 250 Hz
- Low-mids – 251 Hz to 500 Hz
- Mids – 500 to 4,000 Hz
- Highs – 4,001 Hz to 20,000 Hz
- How do Oobleck Monsters react to different volumes?
- How do the different colors of Oobleck react to black light?
- Some smartphone apps offer different types of sound waves. How do Oobleck Monsters react to Sine waves? What about Square and Saw waves?
- When filming your experiment, how do different frame rate settings on your camera impact the clarity of the footage? What happens when you change frame rate? What happens when you change audio frequency?
*Note: Remember, in order to gather accurate data, you only want to test one variable at a time.