How to Grow Beautiful Borax Crystal Hearts for Valentine’s Day

Grow your own Borax Crystal Hearts this Valentine’s Day as a fun holiday-themed science experiment. Your kids will be amazed at the crystal formation!

Borax Crystal Hearts

Growing borax crystals is always a fun science experiment you can do with your kids at home. It’s easy to set up and all you have to do is have patience and wait for the crystals to form.

For this Valentine’s Day, make borax crystal hearts with your kids to show them how much you love them. Your kids will love watching the crystals grow on the pipe-cleaner heart, and how they continue to grow bigger with time!

Is Borax Safe for Kids?

Before we move on to the science experiment, you are probably wondering if borax is safe for kids. I had the same concern and did some research. 

Borax, or sodium borate or sodium tetraborate, is a naturally occurring mineral. People have been using it as an ingredient in household cleaning products such as laundry detergent for years. 

Even though borax is natural, it doesn’t mean it’s completely safe for kids (or adults!). If you are doing the experiment with toddlers who likes to put everything in their mouths, you have to take extra caution to keep borax out of their reach. Ingesting borax may be harmful. 

Children also should not handle borax as it might cause skin irritation. 

Therefore, to safely use borax for this crystal hearts experiment, please:

  • Avoid inhaling borax powder by keeping it at a safe distance from your face.
  • Use gloves when handling borax.
  • Fully clean the surfaces that have come in touch with borax during the experiment.
  • Do not under any circumstances let your young kids handle borax.

Growing borax crystals is fun, but please use proper safety measures! Keeping the safety tips in mind, let’s move on to the experiment!

How to Grow Valentine Heart Borax Crystals


  • 2 cups of water
  • ¼ cup borax powder
  • Pipe cleaners, 1 for each crystal
  • Scissors
  • Wide mouth jar or glass
  • Thread or thin string
  • Popsicle sticks or pencils
Supplies to grow borax crystals

Step-by-Step Instructions:

1. Make the Heart Structure

Twist one red or pink pipe cleaner into a heart shape. Twist the two ends together to make sure the heart does not fall apart.

Make the Heart Structure

Attach a string to the pipe cleaner heart to hang it in the jar.

pipe cleaner heart

2. Prepare Borax Solution to Make Crystals

Carefully pour the borax powder into the wide mouth jar.

Bring water to a boil using a saucepan or electric kettle. Slowly pour the water into the jar (fill the jar about 3/4 full), stirring as you pour. Continue stirring until all of the borax powder is dissolved.

3. Suspend the Heart Structure

Attach the end of the string to a popsicle stick or pencil. Gently drop the pipe cleaner heart into the borax solution so that the pipe cleaner heart hangs in the middle of the jar. The heart should not touch the sides or the bottom of the jar. 

Suspend the Heart Structure

4. Let the Borax Solution Cool (for 24 Hours)

Leave the borax solution to cool overnight. Crystals will start forming as the mixture cools to room temperature. You may be able to see crystals appearing in as little as 2 hours, but it’s best to leave it for 24 hours for more crystals to form.

5. Remove and Dry the Crystal Hearts

Carefully remove the crystal heart from the solution and allow it to dry completely.

6. Enjoy Your Borax Crystal Heart

Once the borax crystal is dry, you can use the thread and hang it up as an ornament. You can also hang them up in the window as suncatchers! Or take the string off and place them in a bowl so your kids can study them.

Borax Crystal Heart

If you have a magnifying glass around, make sure to check out the crystals up close! Your kids will be amazed at the crystal structures that had formed around the pipe cleaner. 

The Science Behind Borax Crystals

How do borax crystals form on the pipe cleaners? 

Borax is a tiny crystal. A crystal is a solid whose molecules are arranged in a repeating pattern. Crystals can form if liquids containing molecules are cooled to a solid structure.

Have you ever made a paper snowflake? Your paper snowflake is an example of what a crystal looks like. Real snowflakes are crystals. The other big word that is important evaporate. Evaporating is when water seems to disappear like a puddle seems to vanish in the summer. Water evaporates as it cools.

We start with hot water because when water is hot, the particles spread out and let lots of borax crystals fit in. They dissolve but they are still there. Think about this like when you put salt on top of buttered popcorn, you can’t see it, but it still tastes salty because the salt is there. The salt crystals dissolved into the butter. In our experiment, the borax dissolved into the hot water.

The ratio of borax powder and hot water recommended above creates a supersaturated solution. That means the solution contains more molecules of borax than the water can hold. 

borax powder into Jar

When we cool the water down, some of the water evaporates, which lowers the amount of water in the jar. This causes more extra borax molecules with no water to attach to. These extra molecules try to go somewhere and stick together to form the pretty crystals that you can see.

Final Thoughts on Borax Crystal Hearts

If your kids like this borax crystal experiment, you can do one for all the holidays! Simply twist the pipe cleaners to whatever shape that fits the holiday (shamrock for St. Patty’s Day, for example). Then follow the same procedures and grow borax crystals for every holiday!

If you have decided that you don’t want to handle borax around your kids, that’s completely understandable. But wait! You can still grow beautiful crystals with salt! Check out how you can grow crystals without borax here.

For more fun Valentine’s Day STEM activities, make sure you check out the fizzing hearts experiment and fishing for hearts activity!

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