Crystal Hearts Valentines Science Experiment for Valentines Chemistry

Growing crystals is actually pretty easy to do at home and makes a great science and chemistry experiment for kids. This Crystal hearts Valentines Science Experiment makes a great science craft and decoration to try with kids. We love holiday themed science and STEM activities, and I think it really helps his love of science to come out!


This crystal hearts Valentines science experiment is a set it up and forget about it kind of experiment like our crystal snowflakes! Growing crystals is definitely a classic science experiment that you must try with your kids! Or check out all the great science ideas you can try for Valentine’s Day this year.


This is a fun to observe chemical reaction for kids! Since you are dealing with hot water, my son watched the process while I measured the solution and stirred. Borax is also a chemical powder and is best used by an adult for safety. An older child might be able to help a little more!


If you want a more hands-on on type of crystal chemistry experiment, try our salt crystal hearts


—-> CHECK OUT: 14  of the Best Valentines Day Science Experiments

  • Borax 
  • Jars or vases (glass jars are preferred over plastic cups)
  • Popsicle sticks
  • String and tape
  • Pipe cleaners

To get started with your crystal hearts, take your pipe cleaners and form them into hearts! Twist two different colors together! Or you can entwine two hearts!

making hearts with pipe cleaners to add to mason jar

Hint: Double check the opening of the jar with the size of your shape! It’s easy to push the pipe cleaner in to start but difficult to pull it out once all the crystals have formed! Make sure you can get your heart in and out easily!

 Use the popsicle stick (or pencil) to tie the string around. I used a small piece of tape to keep it in place. You can do two hearts in one jar but make sure they are small and have room! They would also look pretty if they grew together!

tying pipe cleaner hearts to craft sticks for putting into borax solution


We made these crystal hearts in my son’s 2nd-grade classroom. This can be done! We used hot water but not boiling and plastic party cups. The hearts either needed to be smaller or fatter to fit in the cup.

Plastic cups are generally not recommended for growing the best crystals but the kids still were fascinated by crystal growth. When you use plastic cups, the saturated solution can cool too quickly leaving impurities to form in the crystals. The crystals will not be a sturdy or perfectly shaped.

Also, you need to make sure the kids really don’t touch the cups once they have gotten everything together! The crystals need to remain very still to form properly. Once set up, I recommend making sure you have space away from everything to fit the number of cups you have!


The ratio of borax powder to boiling water is 1:1. You want to dissolve one tablespoon of borax powder for each cup of boiling water. This will make a saturated solution which is a great chemistry concept.

Since you need to use boiling hot water, adult supervision and assistance is highly recommended.

making borax solution for growing crystal hearts

Make sure the heart is fully submerged!

borax solution being added to mason jars for growing crystals on pipe cleaners


The crystals are growing!

You want to set the jars in a quiet place where they won’t be disturbed. No tugging on the string, stirring the solution, or moving the jar around! They need to sit still to work their magic.

pipe cleaner hearts in masons jars filled with borax solution

After a couple of hours, you will see some changes. Later on that night, you will see more crystals growing! You want to leave the solution alone for 24 hours.

Make sure to keep checking to see the stage of growth the crystals are in!

crystals forming on purple pipe cleaner heart

The next day, gently lift out your crystal heart ornaments and let them dry on paper towels for an hour or so…

still wet crystal hearts drying on a paper towel after forming in jars

completely dried and formed crystal hearts


Crystal growing is a neat chemistry project that is a quick set up involving liquids, solids, and soluble solutions. Because there are still solid particles within the liquid mixture, if left untouched, the particles will settle to form crystals.

Water is made up of molecules. When you boil the water, the molecules move away from one another.

When you freeze water, they move closer to one another. Boiling hot water allows for more borax powder to dissolve to create the desired saturated solution.

You are making a saturated solution with more powder than the liquid can hold. The hotter the liquid, the more saturated the solution can become. This is because the molecules in the water move farther apart allowing more of the powder to be dissolved. If the water is colder, the molecules in it will be closer together.


finished crystal hearts with two hearts intertwined together


As the solution cools down there is all of a sudden going to be more particles in the water as the molecules move back together. Some of these particles will start to fall out of the suspended state they were once in, and the particles will start to settle on the pipe cleaners as well as the container and form crystals. Once a tiny seed crystal is started, more of the falling material bonds with it to form bigger crystals.

Crystals are solid with flat sides and symmetrical shape and will always be that way (unless impurities get in the way). They are made up of molecules and have a perfectly arranged and repeating pattern. Some might be bigger or smaller though.

crystal hearts hanging in window like suncatcher

Let your crystal hearts work their magic overnight. We were all impressed by what we saw when we woke up in the morning! We had quite the pretty crystal hearts Valentine’s science experiment!

Go ahead and hang them in the window like a suncatcher!


Make sure to check out these awesome Valentine’s Day science and STEM ideas too. Click on photos.


Leave a comment

Your email address will not be published.