How to Grow a Crystal Rainbow

Learn how to grow a crystal rainbow. This is such a fun STEM experiment for the kids. Perfect for rainbow fun paired with learning, too.

Now that spring is here, it’s time to start thinking about sunshine and all things rainbow. This is why we love this simple crystal rainbow activity. It’s a fun way to let the kids create an experiment that also looks really fun and cool as well.

If you’re looking for a super fun science activity for the kids, don’t miss out on this one! It’s a super exciting way to grow your very own rainbow! We always do this activity during the spring months and it’s just so much fun to do!

The kids look forward to this every single year and they really never get tired of this activity! It’s one that you can easily do in a short amount of time as well.

Do you want more activities? See our list of Colorful Rainbow Activities for Kids.

How to Grow a Crystal Rainbow

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How to Grow a Crystal Rainbow

The really great thing about growing crystals is that it’s an engaging activity for the kids. They’ll love seeing the science behind it to create a really great rainbow as well. The more that they are interested in projects like this, the more that they’re going to want to learn more!

You can easily use this as a fun homeschooling activity or as a fun weekend science project, too. This simple rainbow activity is a great way to try something new and fun.

Who says you have to wait until the rainbows happen outside when you can easily make your own rainbow at home.

If you love this activity, be certain to check out our Rainbow Foam Dough as well.

What is the purpose of growing crystals?

This activity is for fun! It’s also a great way to introduce a simple science experiment to the kids. This will show them that hands-on learning is so much fun to do!

Make certain to have the kids document what they think is going to happen. This can be as simple as documenting what steps they feel is going to happen.

Have them develop a simple thought process of what they think will happen as each hour passes so that they can see how it changes over time.

Do crystals continue to grow?

They won’t but it’s fun to try out that theory with the kids! Have them make notes of what it looks like and then compare it again the next day. This is a simple activity for them to take notes and pay attention to.

Supplies needed for this Rainbow Crystal

how to grow a crystal rainbow

How to grow a crystal rainbow

Make certain to let the kids help out with this. Be there for parental supervision but have them help out with the steps.

Most of these steps are super simple and are great for the kids. They’ll start by twisting together the different colored stems so make certain that they do that to start the project.

how to grow a crystal rainbow

If they’re having a hard time with this step, show them the visual below. Some kids are visual learners and this might be just what they need!

Part of this activity will have to be done on the stove so this is where you come in as the parent. Boil the water and be careful around the kids. You’ll also have to pour this into a jar so be very careful with this as well.

Be certain that you pour in the mixture slowly so it doesn’t break or crack the glass.

how to grow a crystal rainbow

How long does it take to grow a crystal rainbow?

This is actually a quick process. They’ll start making crystals almost immediately but you’ll want to give them at least 24 hours to do their thing fully.

You’ll notice that once that timeframe is up, the growing of the crystals is done.

how to grow a crystal rainbow

Are borax crystals safe?

While this is a great learning project, make certain that the kids don’t try to put this in their mouths. It’s not safe for them to eat or ingest.

Why didn’t my borax crystals work?

If the activity didn’t work, there’s a good chance that the water mixture wasn’t hot enough, to begin with. You want to be really certain that your water is hot so that the borax gets dissolved into it.

What would happen if you put borax crystals back in hot water?

This could be a super fun experiment. Find out what would happen if you put the crystal rainbow back into the hot water.

Would more crystal rainbows start to grow? Or would it wash away the current rainbow cystals? You’ll have to see to find out!

Be careful and do this part of the experiment since you’ll be messing with hot water again.

how to grow a crystal rainbow

How to Grow a Crystal Rainbow

The kids are going to love making this crystal rainbow!


  • 4 cups of water
  • ½ cup of Borax detergent booster
  • Chenille Stems
  • Scissors
  • Deep, wide-mouth jar or glass
  • Thread/thin string
  • Popsicle sticks


Twist the stems into a rainbow shape.

Attach a string.

Put the borax into the jar.

In a medium pan, bring the water to a boil and then pour the water into the jar. Do this slowly so you don't crack the jar. Stir until borax is dissolved.

Put the stem into the solution and put the string onto a popsicle stick. You want the stem to hand in the middle of the jar and not touch the bottom or sides.

The crystals will start to form in about 2 hours. Leave for 24 hours for best results.

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