Quick Cups of Crystals

    Kids, this is a great way to quickly make a large amount of crystal needles!

    Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

    In a cup or a small, deep bowl, mix 1/2 cup of Epsom salts (magnesium sulfate) with 1/2 cup of hot tap water. Stir for about one minute to dissolve the Epsom salts. There will still be some undissolved crystals at the bottom. You have created a "saturated" solution, which means the liquid has dissolved all of the salts that it can hold.

    Place the cup or bowl into a refrigerator. The cup or bowl will fill with needle-like crystals within three hours.

    If you would like to grow colored crystals, you can color the hot water first with a drop of food coloring.


    • Epsom salts can be purchased in drugstores.
    • Don't use boiling water to prepare your solution. Just use water that is as hot as you can make it from a tap. If you use boiling water you will still get crystals, but they will be more threadlike and less interesting. The temperature of the water helps control the concentration of the solution.
    • You can place a small object at the bottom of the cup or bowl to make it easier to remove your crystals, such as a quarter or plastic bottle cap. Otherwise, carefully scoop the crystal needles from the solution if you wish to examine them or save them.
    • As always with science experiments, it's best to wear gloves and eye protection. Don't drink the crystal liquid. It's not dangerous but it's not good for you either. 


    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    October 2013



    Anne Marie Helmenstine at,