Have you ever tried growing borax crystals? This lovely fall activity combines borax crystal science with art, and the results are beautiful. Plus, the process is simple and the crystals grow quickly. Not a lot of waiting involved with these crystals, and kids will say WOW!

Fall Leaf Borax Crystal Science

Borax Crystal Science

Borax (sodium tetraborate) is a naturally-occurring mineral. Like all minerals, sodium tetraborate molecules arrange themselves into a repeating pattern, which creates the crystal shape. Each mineral has its own crystal structure, which depends on the size and shape of the molecules.

In this science project, we’re going to make a saturated borax solution. Water can hold more of a solvent when hot. Then as the water and dissolved borax cool, the water will have to let go of some of the borax molecules that had been dissolved. The borax molecules will then cling to the pipe cleaners and form crystal shapes.

How to Grow Borax Crystals

Growing borax crystals is SO easy! You’ll need a surface to grow the crystals on, and pipe cleaners shaped into fall leaves make the perfect seasonal project.

Supplies Needed:

  • Borax – found in the laundry/cleaning supplies aisle at the grocery store
  • Pipe cleaners – in fall colors
  • Popsicle sticks
  • String
  • Glass jars

First, bend your pipe cleaners into fall leaves. You’ll want a place to attach the string, so make sure each leaf has a short stem. Also, you’ll want the leaves to fit in your jars without touching the sides or the bottom, so keep that in mind when creating your designs.

You’ll need to hang your leaves so that they are suspended in the borax solution. Tie a piece of string to each leaf, and then tie the other end to a popsicle stick.

Once you’ve made your leaves, it’s time to make your borax solution.

I wanted to make a lot of borax solution, so I doubled my friend Sarah’s recipe over at Little Bins for Little Hands and used 3.5 cups of borax and 8 cups of water.

The regular recipe of 1.75 cups of borax and 4 cups of water should be plenty to make 4 or so leaves.

Bring the water to a boil. Then stir in the borax. It’s okay if it doesn’t all dissolve. Just stir until you’ve dissolved as much as you can. You want the solution to be completely saturated, so it’s okay if there’s a little borax left at the bottom of the pan.

Note: I used a regular stainless steel pot, and it was not harmed at all by this experiment! In fact, I think it came out cleaner…

Pour some borax solution into a jar. Then suspend the leaf in the jar. Make sure that the leaf is not touching the sides of bottom of the jar!

In fact, this leaf was a little too big for the jar, and I had to get my teen son to break the jar in order to get the leaf out without damaging the crystals! Oops.

Some of the jars that I had planned to use for this project did not end up being the right shape (too big and would have used up a lot of the solution), so we used some insulated paper cups as well. They worked great!

How fast do borax crystals grow?

This is a great project for kids who don’t like to wait! We were expecting to wait overnight for our crystals to start forming, but we started seeing crystals within 2 hours of setting up our jars!

The little finger in this picture is Janie saying, “Look! I see crystals!”

We took our crystals out of the jar after about 5 hours. Leaving them overnight is totally fine, and might be necessary.

Aren’t they gorgeous?

This one might be my favorite.

Is Borax Safe?

There has been a lot of confusion regarding borax, especially after the slime craze. I truly think that using borax to grow crystals is quite safe. Borax is harmful if you ingest large quantities of it, which won’t be happening here. You also won’t be doing much handling of the borax.

I would recommend not handling the finished crystals more than you need to. The crystals break easily, so you won’t want to allow kids to carry these around and play with them anyway. They are beautiful to make and display! Try making ornaments out of them by adding a piece of ribbon.

Need more Fall STEM Ideas?

Here’s a collection of 10 must-try Fall STEM Activities for Kids. Explore leaves, make pumpkin catapults, create fall leaf tessellations, and more!


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  1. Mr. R Sep 12, 2022

    I love your stuff, especially the lego activities. I actually was inspired to make lego matching cards for patterns and pics for my HS Life Skills class. I really what to do this one with Christmas Trees. I want to see if there is a way to color the crystals before they grow.

  2. Jamie PTO Aug 8, 2023

    What a fun idea! Do you know what happens if you leave leave them in the solution longer? Like over the weekend?
    I’m trying to plan Fall festival activities for STEM elementary school
    Thank you!

    1. Sarah Aug 31, 2023

      I think that would work! Make sure that your designs are smaller than the mouth of your jar. I haven't actually tried this, so you may want to test one out first. The crystals won't grow forever, but I'm not sure at what point they would stop. You'd want to be sure that you can get the leaves out of the jar without having to break it.

  3. Lewonna Sep 21, 2023

    I did this with my 4th graders. We bent the pipe cleaner around Christmas cookie cutters and left them over the weekend. They turned out beautiful and the kids loved them.


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