Try this fun and easy kids science activity! These borax crystal hearts quickly grow in just a few hours. Kids will be amazed to watch sparkling crystals form on their pipe cleaner hearts overnight, and they’ll learn some real chemistry about how crystals grow.
How to Make Borax Crystal Hearts
- 1 hr
- Print this
Ingredients
- 20 Mule Team powdered borax
- pot of boiling waterSupplies
- colored pipe cleaners
- string
- small sticks or skewers
- clean jars
- scissors
- medium pot
Directions
- Step 1
- Shape the hearts – Cut a pipe cleaner in half, twist the ends together to form a circle, then shape it into a heart with your fingers.
- Step 2
- Suspend each heart – Tie a short string to each heart and tie the other end to a stick or pencil resting across the jar, so the heart hangs in the middle without touching the sides or bottom.
- Step 3
- Prepare the borax solution – Boil water and have an adult stir in 4 tablespoons of powdered borax for every 1 cup of water until dissolved.
- Step 4
- Pour and wait – Fill each jar with enough borax solution to fully cover the suspended heart. Check every few hours as crystals form, over 12 hours.
- Step 5
- Dry and display – Remove the heart, pat it dry on a paper towel, and discard the remaining liquid down the drain with plenty of hot water.
The basic project idea is to create a pipe cleaner heart, which is suspended in a water and borax mixture in a jar. Crystals will form on the pipe cleaner within a few hours, and continue to grow if left overnight. Borax crystals are clear, hard, and shimmery. The pipe cleaner color shows through the clear crystals.
Safety note: This activity needs adult help! An adult should handle the boiling water and pour the borax solution. Borax is a cleaning product, so kids shouldn’t eat it or touch the powder with wet hands. Have everyone wash their hands after the project, and keep the jars out of reach of babies, toddlers, and pets. The finished crystal hearts are for decoration, not for little mouths!
How to Make Heart Crystals
1. Shape the hearts
Create heart shapes for the borax crystals to grow on by shaping colored pipe cleaners. Cut a full length pipe cleaner in half. Twist the ends of a half together to create a small circle. Use your fingers to form the pipe cleaner circle into a heart.
2. Suspend each heart
Once you have created some pipe cleaner hearts, tie a short string onto each heart. Tie the other end of the string to a stick, wooden skewer, or pencil. The sticks must be long enough to rest on the top of the jar and suspend the hearts in the liquid. The hearts should hang in the middle of the jar, without touching the bottom or sides. The crystals will “glue” the heart to anything it touches!
3. Prepare the borax solution
Bring a pot of water to a boil. With an adult doing the mixing, stir in 4 tablespoons of powdered borax for every 1 cup of water. Stir until fully dissolved. If a few specks of borax remain at the bottom, that’s okay. This means the water is fully saturated, which is exactly what you want.
4. Pour and wait!
Fill each jar with enough borax water to fully cover the suspended heart. The heart should not touch the bottom or show above the liquid. This will allow crystals to form on the entire shape of the pipe cleaner heart. Now all you have to do is wait! Check your crystals every few hours to see the progress.
5. Dry and display
When you are ready to remove the heart from the liquid, take it out of the jar and pat it dry on a paper towel. Discard the rest of the borax liquid down the drain with plenty of hot water, and wash out the jar.
Borax crystal hearts are colorful and shimmery, thanks to the bright pipe cleaner colors inside!
The Science: Why Do Borax Crystals Grow?
Here’s the fun teaching moment for curious kids. Growing borax crystals isn’t actually a chemical reaction, because nothing new is created. Instead, it’s a physical change called crystallization, which is all about temperature.
Hot water can dissolve much more borax than cold water can. When you stir borax into boiling water, you create a supersaturated solution, water holding more dissolved borax than it normally could. As the water slowly cools overnight, it can’t hold onto all that borax anymore. The borax particles come out of the solution and attach themselves to the pipe cleaner, stacking together in neat, repeating patterns. That orderly stacking is what makes crystals look like tiny gems!
Homeschool extension ideas: Have kids predict which will grow bigger crystals: a jar that cools slowly (wrapped in a towel) or one that cools fast (near a cold window), then test it. Slower cooling usually grows larger crystals. You can also compare borax crystals to salt or sugar crystals under a magnifying glass and spot the different shapes.
Troubleshooting Tips
- No crystals after several hours? The solution probably wasn’t saturated. Solve this by reheating the solution and stirring in more borax, then try again.
- Crust forming on top of the water? That’s normal! Crystals form fastest where the water cools first. Gently break the surface crust so the heart below keeps growing.
- Heart stuck to the jar? Next time, center the heart so it hangs freely. If the crystal heart is stuck, you can loosen it with a little warm water.
Find more creative activities for kids on our Kids Activities page!
Hi, I’m Katie! I’m a homeschool mom who’s traveling the world with my husband and 4 kids. We raised our family in North Idaho and currently live in Mérida, Mexico. I love Jesus, coffee, creative projects, photography, and traveling. I hope you enjoy our creative ideas and family adventures!
