Growing crystals is such a magical experience but the long wait can be hard for younger kids. Fortunately, we've got a crystal garden that will grow overnight in your refrigerator so you can wake up to beautiful crystals tomorrow. Leave them clear or add a few drops of food coloring to make crystals in a rainbow of colors!
This project uses Epsom salts, which are safe to handle and available in almost any drugstore. (Just don't eat it, obviously!) Because these Epsom salt crystals grow so quickly and easily, this project invites experimentation. You can try using containers of different sizes and shapes, and test out how big the crystals get if you leave them to grow for longer or shorter periods of time.
How we did it:
- epsom salt
- glass cup or jar
- 1 cup hot/warm water
- mixing bowl
- food coloring or liquid watercolor
Pour 1 cup of hot tap water and 1 cup of epsom salt into a mixing bowl.
Stir well for 1-2 minutes. There will be some salt crystals left at the bottom of your bowl.
Pour the liquid into your jars or cups, making sure you get some of the undissolved crystals into every jar or cup. These will help to seed your garden, giving your crystals a place to start growing. If you'd like to color them, add a drop or two of food coloring or liquid watercolor to your jars and give them a stir. Place your jars of crystal liquid into the freezer for 10 minutes. Then move them to the refrigerator and leave them undisturbed overnight.
Check for crystals after they've spent the night in the refrigerator. Sometimes it helps to tip the liquid back and forth a bit to see the crystals. If you are happy with them, pour off all of the liquid and wipe the top of the glass above the crystals so the leftover liquid doesn't cloud the walls of the jar.
What's going on?
When you mixed up equal parts of Epsom salt and hot water, you made sure that the water was as full of as much salt as it could hold. That's why you ended up with little bits of salt at the bottom of the bowl—the water was so full of dissolved salt, no more could fit in.
Cooling the water in the freezer helps to kick off crystallization because cold water can hold less salt than hot water. As the water cooled down, the salt had less and less room to stay dissolved. Eventually, the salt started to get pushed out of the water—essentially, the salt un-mixed itself! The bits of salt falling out of the water grew together to form the crystals you saw. This is called crystallization.