Simple Crystal Gardens

The finished product .
One of the steps.

Everybody loves crystals. Growing crystals seems like a magical process. It is actually quite simple.

Materials needed: epsom salts, food colour, spoon, glass bowl or jar, hot water, small rocks (*sand or glitter works too), patience

Step 1    Add about 250 ml epsom salts to 250 ml hot water. Put in a few drops of food colour too. Stir. For a long time. Keep stirring until all the epsom salts have dissolved. If they dissolved easily into the water, add a little more and keep stirring. You want to dissolve as much epsom salts as possible into the mixture. Expect to stir for at least 5 minutes.

Step 2    Put the small rocks* into a glass bowl and pour the epsom salts mixture over the rocks.

Step 3    Put the glass bowl with the rocks and mixture in the freezer for ten minutes.

Step 4    Take it out of the freezer and put it in the fridge now. It will need to stay there at least until the next day.

Step 5    After waiting 24 hours, take it out of the fridge and check if crystals have formed. If they have not yet formed, repeat this step until they have. 

(Note: if crystals never form, the solution was not super-saturated meaning that not enough epsom salts were dissolved in the water.)

The science:    Epsom salts are magnesium sulfate. In this activity, you are "super-saturating" the mixture (solution). Super-saturation takes place when you dissolve a lot of something in hot water. Because the water is hot, more epsom salts can be dissolved into the water. When you cool the solution down, it has more magnesium sulfate than it can hold. That makes it a super-saturated solution. The extra magnesium sulfate molecules will come out of the liquid solution and stick to something. The rocks (or sand or glitter) will be what the molecules stick to. Where the magnesium sulfate molecules stick to is called a nucleation site. The magnesium sulfate forms crystals because the molecules line up in patterns.

Notes    If you have tried using small rocks and it worked, switch to sand or glitter. The results may be different. See what other materials work. And please email me your results or leave a comment.

The Results    So the crystals turned out great. I hope to try again soon with other materials for the nucleation site.

Once again, here is a closeup of the crystals.