A stalagmite (from Greekσταλάσσω — „to drip“ or “that which drips”)…. or a lesson in the origins of cave formations.

You will need:

2 glass jars

baking soda

a string of thick yarn (we made ours thicker by braiding several strings together)

hot water

a plate

Fill up the jars with hot water. Add 6 full tbsp of baking soda and stir well. Put the jars in a warm place where you wouldn’t have to move them. Place the plate between them. Soak the ends of the yarn string in the two jars so that the middle hangs over the plate.

Our experiment took 5 days… and it keeps covering with more crystals with each passing day. We stir the solutions from time to time. 


The solution from the jars soaks up the yarn string and starts dripping on the plate. The water gradually evaporates and the baking soda turns into crystals. 

Cave columns, called stalactites and stalagmites, are made in the same manner. Rainwater seeps through the ceiling, bringing along dissoved minerals from the rocks it has passed through. The water evaporates, the minerals remain. They accumulate in the course of thousands of years, making beautiful rock formations.


experimentsfor kids