This rainbow crystals science fair project idea is a fun and easy science experiment for kids,  perfect for home or school (see hints below).   Grow your own rainbow crystals with just a few simple ingredients and watch the AMAZING crystals grow overnight.

Who knew that it would be so simple to make rainbow crystals?   With just a few simple ingredients and some science exploration, this science experiment for kids is certain to be at the top of their favorites list.


Rainbow Crystal Science Fair Project for Growing Crystals


Growing your own crystals is a really cool science activity for kids. There’s not a lot of hands-on experimentation with this science activity, but it’s pretty neat to observe the changes taking place. Plus, you can hang the rainbow crystals in the window like a sun catcher when you are finished.

Who doesn’t love to see a rainbow crystal literally grow right before their eyes?

We love to grow crystals for all the holidays and seasons. Plus, you don’t have to use just pipe cleaners either. We have tried seashells, egg shells, and even evergreen branches!  Learn how to grow borax crystals with pipe cleaners too!

One of our favorite types of crystal are these CRYSTAL SEASHELLS.  They’re just gorgeous and such a fun science experiment for kids!



Let’s learn how to make borax crystals using pipe cleaners as the base! Just a few simple ingredients and you can grow your own crystals easily!

Looking for easy to print activities, and inexpensive problem-based challenges? 

We have you covered…

Click below to get your quick and easy STEM challenges. 

Free Rainbow STEM Challenge Cards



  • 9 TBL Borax (found with laundry detergent)
  • 3 Cups Water
  • Jars or vases
  • Popsicle sticks
  • Pipe cleaners in rainbow colors

 Rainbow Crystal Supplies with Borax and Pipe Cleaners


Let’s flex those STEAM skills. STEM plus Art = STEAM! Give the kids a handful of colorful pipe cleaners and let them come up with their own version of a rainbow. Include white pipe cleaners if they want to include clouds.

Note:  This is a variation of our original rainbow crystal project which did not have clouds!

Build a rainbow out of pipe cleaners to grow crystals

rainbow made from pipe cleaners

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 rainbow pipe cleaners in and out easily!

Use a Popsicle stick (or pencil) to tie the string around the pipe cleaners. I used a small piece of tape to keep it in place.


NOTE: Since you are dealing with hot water, adult assistance is highly suggested!

  1. Boil the water.
  2. Measure the Borax into a bowl.rainbow crystals
  3. Measure and pour boiling water into the bowl with the borax powder. Stir the solution.
  4. It will be very cloudy looking.
  5.  Carefully pour the liquid into a jar (or jars).making borax crystals step by step
  6. Add a pipe cleaner rainbow to each jar and make sure the rainbow is fully covered by the solution.
  7. Place the jar/s in a safe place where they won’t be disturbed.

growing crystals with borax and pipe cleaners final stage


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.

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.

fun crystal science fair project with crystal rainbow theme science

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

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

grow your own crystals


We made these crystal rainbows in my son’s 2nd-grade classroom. This can be done! We used hot water but not boiling and plastic party cups. The rainbow pipe cleaners 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 the 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 as 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 store the number of cups you have!



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.

rainbow crystals

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.

Let your rainbow crystals work their magic overnight. We were all impressed by what we saw when we woke up in the morning!  Go ahead and hang them in the window like a suncatcher!




Rainbow In A Jar

How To Make Rainbow Slime

Rainbow Activities

Make A Walking Rainbow

Rainbow Science Fair Projects 


Looking for easy to print activities, and inexpensive problem-based challenges? 

We have you covered…

Click below to get your quick and easy STEM challenges. 

Free Rainbow STEM Challenge Cards



  1. Wow, I am so thrilled with the science projects – I’m on my way to get liquid starch as soon as I finish commenting! I can’t wait to try the rainbow slime as well as the crystals. I have a question about ages – what’s the youngest child you’ve successfully done these projects with? As a family based preschool and child care, I have a mixed age group – from 8 months to twin 5 year olds who come 2 afternoons a week.

    One of the many challenges is to find something everyone can do, to some degree or another.

    And thank you so very much for the pictures – as clear as your explanations are, seeing the actual thing is definitely worth a thousand words! I’m on the board of the county wide association for licensed providers – you can be sure that I’ll pass on your site to all of our members, and other groups, such as the local Association for the Education of Young Children and the National Association for Family Child Care. Absolutely great job!

  2. For slime, the youngest I have done it with is 4 and everyone usually has an adult with them. We had a slime party. My son at 5 would do fine watching me and copying my instructions. Many of my other science activities go back to when my son was 3. He does not try to put things in his mouth though. You could definitely make baby safe sensory play ike cloud dough with flour and oil too. Making plastic discovery bottles would be awesome for all the ages!

  3. I was wondering how much of the mixture do you pour into a quart size jar? I mixed up the 9 TBLspoons and poured the 3 cups of hot water in the jar and then put thepipe cleaners in it. I am wondering if that is too much?

  4. You just need to fill the jar enough to cover your pipe cleaners completely.

  5. Hi! Question: can you premake the water borax solution? For example could I prepare the hot water and mix the borax a couple hours before I was to put in the pipe cleaners? Or do the pipe cleaners have to go in while the water is hot?

    Thank you !

  6. Unfortunately, you need to add to the pipe cleaners when the water is hot as the hot water is part of the chemical reaction!

  7. Fill with hot water and it will loosen the hardened material. Wash down drain and put glass jars in dishwasher!

  8. after its all done is it stafe to touch and play with the crystals from pipe cleaner and the shells

  9. I am mother of two and i was finding some science experiment which i can use in my homeschooling and i came across to your blog.This is awesome i will definitely try the Rainbow crystal experiment with my children.

  10. Do you keep the pipe cleaner creation submerged overnight or dunk, remove and let dry?

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