How can you keep paper towel dry under water? It seems impossible to keep a piece of paper towel from getting wet when submerged in water, but that’s why this science experiment is so great to do with your kids.
This amazing kids science trick looks like magic, but it’s actually based on a scientific concept called air pressure. It’s thrilling science experiments like these that make my kids super excited whenever they hear that it’s experiment time!
Plus, this dry paper towel experiment is simple to set up and uses materials you probably already have at home. Your kids will want to do it over and over, and you can repeat this experiment with different containers and cups.
Read on to learn how to perform this STEM experiment and keep your paper towel dry underwater with atmospheric pressure.
Keep Paper Dry In Water Science Experiment
- Paper towel
- Clear cup or glass
- Clear container (it needs to be bigger and ideally, deeper than the cup)
- Optional: food coloring
1. Stuff some paper, tissue, or paper towel into the bottom of the cup. You may need to rip the paper towel if you are using a smaller cup. Make sure that there is enough paper towel and that you wedge the paper towel in the cup tight enough so that when you flip the cup over, the paper towel wont’ fall out.
2. Fill the container with water. The water level should be higher than the height of the cup. The experiment will still work if you don’t have a container taller than the cup, but it won’t be as impressive.
Squeeze a couple of drops of food coloring in the water and stir. This is an optional step, but it does make the water and cup (once submerged in water) easier to see for the kids.
3. With a steady hand, flip the cup upside-down and lower the cup straight down into the water. Note: The cup needs to be perfectly straight when you place it into the water. If you tilt the cup even just a little bit, you will see air escape the cup and the paper towel will get wet.
4. Pull the cup straight out of the water. Hold the cup in mid-air above the container for a few seconds to let the water drip off the cup.
5. Flip the cup back over and check the inside of the cup. Did the paper towel stay dry? Remove the paper towel from the cup for closer observations.
Did your paper towel stay dry after being underwater?
When I was setting up the experiment, my kids did not believe me when I told them that the paper towel would not get wet even after being submerged in water. Imagine their surprise when I pulled the cup out and the paper towel was completely dry!
This science experiment is easy enough for even preschoolers and kindergarteners to try. After you show them how to hold the cup steady and insert it straight into the water, they should be able to repeat this experiment over and over again.
You may want to keep extra paper towels around to wipe off the cup after your kids take it out of the water. They may not have the patience to wait for the liquid to drip off the cup to see if the paper towel got wet!
As you may see in the picture, my fingers got a bit red from the red food coloring. You may want to wear gloves if you decide to mix food coloring with water.
Science Behind Why the Dry Underwater Paper Towel Experiment
This is an excellent experiment to show your kids that air does take up space. Even though we cannot see air with our naked eyes, the air is made of particles and it has mass and volume.
Atmospheric pressure is the force exerted by the weight of the atmosphere of the Earth. When you place the cup upside-down in the water, the atmospheric pressure pushes down on the water, preventing it from entering the glass. As a result, the water cannot get to the bottom of the cup and the paper towel remains dry.
However, if you tilt the cup just slightly, the air inside the cup will escape in the form of bubbles. In turn, there is no enough air pressure exerted on the water. As a result, water rushes into the cup and your paper towel is now wet.
You can have your kid try placing the cup into the water crooked just to demonstrate what happens when there is not enough air pressure inside the cup. You can also try with all sorts of cups to test if atmospheric pressure will always keep the water out when the cup is lowered straight into the water.