Crystal Cubes and Needles

    Kids, did you ever want to grow your own crystals? This experiment will show you how to make crytals with different shapes.  

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

    You will need 2 saucers, 2 sheets of dark construction paper, 2 baby food jars with lids, epsom salt, and ordinary table salt. Fill the jars half-full with water. Add 2 tablespoons of epsom salts to one jar, and 1-1/2 tablespoons table salt to the other jar. Secure the lids, shake vigorously 60 times each, and then let them settle for several minutes. Cut circles from the paper to fit inside the saucers. Separately, pour thin layers of the salt solutions over the separate pieces of paper; try not to pour out any of the undissolved salts. Place them in a warm place and wait several days, observing daily.

    On the paper wet with the table salt (sodium chloride) solution, you should see small, white, cubic crystals that increase in size each day. Sodium chloride salt crystals have a cubic shape. You should see long, slender, needle-shaped crystals on the paper wet with the epsom salt solution. "Epsom salts" is the common name for this chemical, but it is also called magnesium sulfate. When epsom salts are packaged, the needles of magnesium sulfate are first crushed. By dissolving in water and then allowing for slow evaporation, the needles and cubes are given the chance to build in size.   


    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    May 1993


    Reference: "Chemistry for Every Kid" by Janice VanCleave, Wiley: NY, 1989.