Travis has seen stalactites and stalagmites in cartoons and real life, so he was intrigued when we set out to make our own. You’ll need about a week for this project from start to finish, so it’s also a good lesson in patience!
For set up, add 1/4 cup Epsom salts to each of two paper or plastic cups. Fill with water and stir for 1 minute. There should still be some Epsom salts undissolved in the bottom, making this a supersaturated solution.
Add food coloring in your child’s colors of choice. Travis stirred in blue and green.
Tie a piece of yarn around two paper clips (or safety pins), and dangle the ends in the cups. Now set the whole contraption some place where it can sit undisturbed with the yarn dangling over an old jar lid between the two cups.
Alas, we didn’t have great results with this. Either something is wrong with Epsom salts in our apartment these days, or we’re making a mistake! But we could see crystals growing lightly along the string.
Interestingly, there was a leak in one cup and the best crystals formed around the base. So Travis declared these our stalagmites.
As a side note, we could also see the blue food coloring creeping up the yarn: capillary action in action!