overnight crystals

Overnight Crystal Garden

Despite the wait time, my boys love experiments where they can anxiously wait to see what happens when something is left to grow. Crystals are neat – they look like little tiny snowflakes or fragile glass. We colored ours so it had a neat effect. We were also curious to see these crystals form from just using Epsom salt! That was an ingredient we had never used before in a science experiment. I would recommend using a few jars to be able to see any differences in crystals!


overnight crystal garden ingredients

  • Epsom salt
  • Clean glass jars
  • Food coloring (optional)
  • Bowl or glass measuring cup
  • Spoon
  • Pebble or Sand
  • Microwave (optional)


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.

making overnight crystals

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.

Notes: Don’t overheat the water! Ones heated more than 45 seconds may not develop. Do try to stir for 1-2 minutes to get as much salt dissolved as possible. DO NOT let them sit in room temperature. Crystals will deteriorate.

overnight crystals in a jar


If you are using color, as we did, add a dash of food coloring to the water. Stir.

overnight crystal garden in progress

Pour the water into the jar with the salt. Stir the salt and water for 1-2 minutes to dissolve the salt. Don’t worry if some of the salt remains undissolved at the bottom of the jar.

differently colored overnight crystal gardens

Drop a pebble or a few grains of sand. Crystals need something to grow on and one little impurity in the water like grain of sand should help ensure they have a place to nucleate.

Place the jar in the back of the refrigerator. Alternatively, quick cool the mixture for 10 minutes in the freezer and then move it to the refrigerator. There is a slightly less success rate going straight from mixing to the fridge.

overnight crystals in the fridge

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.

overnight crystals freezing

Carefully pour out the extra liquid. It’s okay to leave a little liquid at the bottom. 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.

blue overnight crystals red overnight crystals green overnight crystals

Use a wet paper towel to gently wipe away excess salt and water that may be on the upper portion of the jar. Be careful not to damage any of your crystals! Touching them may easily damage them.

As I mentioned at the beginning, it was neat to see what the Epsom salt and water could form! We didn’t know that the two together would form these beautiful crystals. My kids were amazed!

closeup of overnight crystals child looking at overnight crystal garden chilled overnight crystals

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