Vanishing Jelly Marbles
Clear, polymer-based water marbles that vanish like magic in a glass of water
It looks like an ordinary glass of water, but hiding just below the surface of the water is an amazing collection of large, jelly-like marbles that become invisible when submerged in water. The Jelly Marbles become invisible due to an identical index of refraction with the liquid. In other words, they vanish like magic! As you’ll see, there’s more to this experiment than meets the eye.
- Jelly Marbles
- Clear dish
- White plastic scoop
- 9 oz plastic cup
- Adult supervision
- Use the white scoop to pour one teaspoon’s worth of dry Jelly Marbles into the 9 oz plastic cup.
- Fill the cup with water. Good quality water that does not contain high levels of iron or minerals is best. If you’re uncertain as to the quality of your tap water, invest a small amount in distilled water at the grocery store. You’ll see a difference! Set the cup aside in a warm location for several hours. It’s OK to check on their growth now and then but be sure to wash your hands before touching them so you keep the water and the marbles clean. Dirty water and grubby mitts are not their friends. To be safe, you might want to use a spoon.
- After about five hours, the Jelly Marbles should be fully grown. Clean hands? Great! Reach into the cup and gently scoop up a handful of Jelly Marbles. You’ll be amazed at their final size! Look at one closely and then drop it back into the water. It vanishes! You’ll have to grab it again to make sure it’s really there. Add these Jelly Marbles to the clear dish. Grow and add more to the dish until you have completely covered the bottom of it.
- Write a message or place a picture under the clear dish. Challenge someone to read the message or describe the picture. When they give up, fill the dish with water and watch them gasp as the message becomes crystal clear.
How Does It Work?
Jelly Marbles start out as tiny, hard spheres but, add water and the super absorbent polymer they are made from absorbs 300 times its weight in water. These hydrophilic (water loving) spheres are approximately 99% water when fully hydrated. If you look closely at a sphere in a bowl of water, you can barely see its outline. That’s because light passing through the sphere is refracted (or bent) only a tiny bit along the edge of the sphere. Without this refraction along their edges, Jelly Marbles would totally vanish altogether.
The water-filled spheres become invisible due to having an identical index of refraction with the water in the bowl. The secret to keeping them this way is to keep the Marbles clean and free of dirt and oil from your skin. The more the spheres are handled, the more visible they become because dirt and oils on your skin are transferred to the surface of the spheres. This increases the amount of light reflected from the spheres and reveals them.
In the hidden message demonstration, the message looks scrambled under the hydrated spheres because the light reflected off of the message is scattered in every direction by the water-filled Jelly Marbles. It’s like trying to read through broken glass; in other words, impossible! When water is added to the dish, the light rays pass straight through the water and the spheres into your eyes without being scattered. This is due to theJelly Marbles’ identical index of refraction with the water. So, it seems like you’re looking through a dish of plain water and can easily read the message. It’s as close as you’ll get to solid water at room temperature.
A Fun Twist – Ghost Eggs
Now that you know the science behind these vanishing marbles of water, you can make the experience even more fun with a Halloween spin. The application is up to you but we think that Jelly Marbles, and their amazing ability to vanish under water, is the perfect way to teach the properties of light during the Halloween season. What other fun twists can you think of?
Vanishing Jelly Marbles Secret Science Fair Connections
Making Jelly Marbles “vanish” is a pretty cool trick but it’s not a science fair project. You create a science fair project by identifying and testing variables. A variable is something that might change the outcome. Let’s take a look at some of the variable options you might test and write up for a science fair.
- Test liquids other than water. What’s different about a Jelly Marble reaction in orange juice, milk, soda, vinegar, bleach, coffee, tea, ketchup, etc? In which of these liquids do they grow the fastest? slowest? not at all? What’s the same about each test? What’s different? How long does the reaction take in each one?
- There are many different kinds of water to test, e.g. tap, bottled, sparkling, distilled, spring, rain, different concentrations of salt water and/or sugar water, etc.
- What changes do you detect in the reaction using colored water? Why might that happen?
- What happens to the reaction time if you raise or lower the temperature of a test liquid?
- Get seeds for a fast-sprouting plant such as grass, radish, or beans. Use three clear cups and fill one cup with just potting soil, another with a half-and-half mixture of potting soil and hydrated Jelly Marbles, and fill the last cup with all Jelly Marbles. Plant the same kind of seed in each cup and find out which potting material helps the plants sprout fastest and grow the most. Check the progress of your plants every day or two. The results may surprise you.
These are just a couple of ideas and you certainly aren’t limited to them! Come up with your own variable to test. Remember, you can change only one variable for each test while making sure that all the other factors in your test remain the same!