Science for Kids: Overnight Crystal

Science for Kids: Overnight Crystal Garden
Any exploration of science for kids is not complete without growing some crystals….am I right? In fact, at the science fair this past year crystal growing projects were the project de jour, and I can understand why, growing a Crystal Garden has ranked pretty high up there on my list of fun science experiments since I myself was a kid!
Now one of the big drawbacks to many crystal growing projects is the time involved. I’ll be honest, I am not a patient woman and though I proselytize patience to my kids, I’m not a very good example of this virtue! So days of waiting for a crystal garden to grow pretty much sent this idea to the “someday” list. That is until I discovered Epsom salt crystals….leave them overnight and wake up to magic! Oh how much do I love thee Epsom Salt!
To be fair, growing crystals using Epsom salt will not yield giant geodes bursting with color; Epsom salt crystals are small, delicate, and slivery. Instead of one or two mega crystals this science experiment for kids will give you hundreds of miniature crystals, they look a little bit like shards of glass and if you’re lucky you may get a few that look like snowflakes…We experimented quite a bit with this project to get good results and despite repeating the process exactly the same we had about a 70% success rate with crystal growth each batch we made. So plan on making 3-4 crystal gardens in case 1 or 2 don’t grow. Another upside to making a few gardens at once is seeing how differently they grow, some crystal gardens were delicate and lacy, other were more rocky and gem like. Be sure to make a bunch to delight you and the kids!
Materials
Epsom Salt
Clean Glass jars or round glass votives like these
Liquid Watercolors (optional) Note: these are concentrated so a little goes a long way; these are one of the best art supplies you can invest in!
Water
Bowl or glass measuring cup
Fork
Microwave (optional)
Step One | Measure You will be using a ratio of 1:1 water to Epsom Salt for this project. Add 1 cup of Epsom salt to your jar/votive. If you are working with larger jars feel free to add more salt but be sure to make a note of how much so you can add the same amount of water.
Step Two | Heat the Water Add 1 cup of water to a microwave safe bowl. Heat the water in the microwave for 45 seconds. Alternatively use very hot tap water and skip the microwave.
Step Three | Add Color If you are using color, add a dash of liquid watercolor to the water. Stir.
Step Four | Combine Pour the water into the jar with the salt. Do this quickly so that the water is warm. Stir the salt and water for 1-2 minutes to dissolve the salt. We stirred for 2 minutes on most of our experiments. Don’t worry if some of the salt remains undissolved at the bottom of the jar
Step Five | Cool Place the jar in the back of your refrigerator. Alternatively, quick cool the mixture for 10 minutes in the freezer and then move it to the refrigerator. Cooling in the freezer first yielded crystal growth in 90% of our experiments. We had just a slightly lower success rate going straight from mixing to the fridge.
Step Six | Let ’em Grow Leave the mixture overnight in the fridge. Crystals may start forming in as little as 3 hours but we got the best results when we made the gardens in the evening and left them to sit undisturbed overnight Bonus: My daughter was excited to wake up and see how they had grown!
Step Seven | Result Time Carefully pour out the extra liquid. It’s okay to leave a little liquid at the bottom of the jar. If you colored your water it will be hard to see if any crystals have grown until the excess liquid is removed. Clear water is easy to check.
Step Eight | Clean Use a wet paper towel to gently wipe away excess salt and color that may be on the upper portion of the jar. This will help you see the lovely crystal garden through the glass. Be careful not to damage any of your crystals!
You’re done! Hand the kids a magnifying glass for additional exploration. My kids really wanted to touch the crystals. That’s okay but let them know they are delicate and break easily.
Tips
Science for kids is not without trial and error! Here are some tips I learned after repeating this experiment over 20 times…

There will be duds. I did this experiment many, many times, mixing up some of the variables, but the only constant was that I always had a few instances where the crystal would not grow. I’m not a chemist and I’m sure there is a reason why one mixture grew and another did not despite me thinking I had done the exact same experiment….So hedge your bets and make a few of these at one time. UPDATE: A few scientists have replied to this post and recommend dropping a grain of sand in each batch. Crystals need something to grow on and one little impurity in the water like grain of sand will should help ensure they have a place to nucleate.
Don’t overheat the water! I know it’s tempting to really heat that water