Summertime, soaking up the … water!

Seen as it’s now officially summer, we’ve been soaking up the sun when we can, and this gave us some inspiration for science experiments. However, instead of the sun we’ve been soaking up water, using water beads.

This blog is brought to you by our guest contributor, Toby.

What are water beads?

Water beads, also known as water crystal gel, are composed of a polymer that can absorb large amounts of water. A polymer is a very long molecule, and the polymers in water beads can typically absorb up to 200 times their weight in water. Water beads are usually made from a polyacrylamide such as sodium polyacrylate, which is commonly known as a superabsorbent polymer or slush powder in dry form. Water beads are readily available from gardening stores, florists and online sources such as Crystal Water Beads.

Plants growing in water beads

Plants growing in water beads. Photo: Crystal Water Beads (All Rights Reserved)

Water beads are most often used for watering plants, especially potted plants. They conserve water because the beads release the water slowly over time. This property is also helpful for providing water to small animals, which can drown in an open container of water. Water beads are also used to make artificial snow and colorful decorations. Slush powder has an absorbent filler for disposable diapers and controlling floods.

However, we’ve been using them to demonstrate some interesting science!


Invisible Marbles

This experiment shows how to make the marbles almost invisible!

You will need:

  • Water beads
  • Tall, clear container
  • Water

Soak the water beads in water until they’re the size of a small marble. Fill the container with water and place the hydrated beads into the container. The beads will sink to the bottom of the container and become nearly invisible. Reach your hand into the container and try to pull the hidden beads out of the water.

What’s going on?

The water beads are more than 99% water when they are completely hydrated. Different materials bend light waves by different amounts when the light waves pass through the material, a property which is known as the material’s refractive index. The water beads have the same refractive index as water, which is why you can’t see them when they’re in the water. Air and water have different refractive indices, which is why you can see the beads when you take them out of the water.

Want to see our director Wendy Sadler trying this out on television? She was on ITV’s Alan Titchmarsh show doing just that, as well as other science experiements:



Hidden Picture

This experiment also uses water beads to demonstrate the property of refraction.

You will need:

  • Color photograph
  • Table
  • Clear glass tray
  • Water
  • Water beads

Place a photograph on top of a table with the image facing up, and put the tray on top of the photograph. Put enough hydrated water beads in the glass tray to fill the tray with several layers of beads. The image will appear to be blurry blobs of color. Fill the tray with water to see the picture come into clear focus.

What’s going on?

The light waves bend multiple times as they pass between the water beads and the air pockets between the beads, causing the image to appear distorted. These air pockets disappear when you fill the tray with water, which causes the light to pass through the water and beads without bending. This makes the picture become clear.


There are many similar effects you can achieve with water beads and light distortion, not to mention with absorption. Give it a go and see what you can do yourself.

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