Grow your own crystals in a cup

See them sparkle! See them shine!

Growing your own crystals can be a laborious and delicate process, occupying several days. This super-easy recipe requires just two household ingredients, and will yield a whole cup of needle-like crystals in just a few hours. Get to work. Your child’s face will light up as they watch their creation grow!



  1. Grab your beaker, and help your child to stir half a cup of epsom salts with half a cup of hot (but not boiling) tap water. They should stir as much as they can, for at least a minute. This process will create a saturated solution, meaning no more salt can dissolve, though some undissolved crystals might still remain at the bottom of the glass.
  2. If you’d like your crystals to be colourful, add a few drops of food colouring.
  3. Put the beaker in the fridge.
  4. Check on the beaker in a few hours. It should be full of dazzling, delicate, needle-like crystals! Pour off any excess mixture to examine them up close.
  5. Explain why this has happened* to your child, if they are unsure of how it works.

*Epsom salt is another name for the chemical magnesium sulfate. The temperature of the water determines how much magnesium sulfate it can hold; it will dissolve more when it’s hotter.

Cooling the solution rapidly encourages fast crystal growth, since there is less room for the dissolved salt in the cooler, denser solution. As the solution cools, the magnesium sulfate atoms run into each other and join together in a crystal structure. Crystals grown this way will be small, thin, and numerous. Larger crystals will take longer to yield.