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    Home / Science projects / Make Stalactites and Stalagmites
    • Make Stalactites and Stalagmites

      Make Stalactites and Stalagmites

      Caves are full of mineral deposits that form unique shapes, such as the icicle-like stalactites (which hang from the ceiling) and stalagmites (which rise up from the ground). (To learn more about cave rock formations, go to our Stalactites, Stalagmites, & Other Cave Formations Teaching Tip.) Make your own stalactites and stalagmites with this project! (Adult supervision recommended.)

      What You Need:

      What You Do:

      1. Cut two 24' pieces of cotton string or wool yarn, and tie one metal washer to each end to act as a weight.

      2. Fill four small glass jars or beakers 2/3 full with very warm (120-140 °F) water. Stir in as much baking soda into two of the jars as will dissolve; do the same with Epsom salt in the other two jars. Put the jars in a warm place where they can sit undisturbed for about a week.

      3. Next, place a small plate between each set of jars and put the ends of one string in the baking soda jars with the middle of the string draping in a 'u' shape just above the plate. Do the same with the Epsom salt.

      After a few days, check to see if any material has built up on the string. An icicle-like formation should form downward on the string and upward on the plate. Real stalagmites and stalactites are formed in almost the same way, by mineral-containing waters dripping in caves until a deposit of calcium carbonate builds up...or down, as the case may be.

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    By: Cathy Fasano
    Date: Mar 14, 2015

    Do you run a string from soda to soda as one set and salt to salt as the other, or do you run two sets of soda to salt?  The instructions seem to say the former, but the latter makes more sense.

    By: Warda farooq
    Date: Feb 18, 2015

    Very nice and attractive experiment
    I wanted to know if I can use only baking soda instead of Epsom salt
    Or it not could I know what is Epsom salt and from where to get it ???

    By: Tereza
    Date: Nov 04, 2014

    Thank you so much! I finally found a good science project experiment!