Cotton Crystals




Introduction: Cotton Crystals

About: Currently a Master of Architecture graduate student. But above all, I am a maker.

I originally made these crystals for an experimental architecture project that stemmed from a curiosity in growing rigid structures around a soft substrate scaffolding. (Graduate school drives you to question all sorts of things!)

Typically Borax crystals are grown on something like pipe cleaners where the scaffolding is left inside and is a direct reflection of the resulting growth. I found this method of formwork too predictable. I thought, is there another material Borax would crystalize on that would produce a new form?

The resulting project is quick and incredibly satisfying! The prep work takes about an hour, followed by a wait time of about eight hours (or overnight), and then an hour of finishing touches!

This is a great project to learn all about crystals! What are crystals? How are they formed? What sort of scaffolding produces the best crystals?

Make sure to share your projects! I'm curious to see how these Cotton Crystals turn out!

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Gather Supplies

Gather a couple simple supplies to grow your own Cotton Crystals!

1. Borax (20 Mule Team Borax Laundry Booster) This is the main ingredient in growing your crystal. I purchased this box from Lucky's grocery, but you can find it at most big-box groceries, some hardware stores and even on Amazon.

2. Cotton balls

2. Chopsticks (or fork) and a stirring spoon

3. Water

4. Heat safe bowl (> 2in deep) You want something deep enough to submerge the cotton balls. I picked up this Pyrex bowl at Goodwill for a couple bucks because I didn't have a clear container. I was able to watch the growth through the glass and satisfy my curiosities without agitating it.

Step 2: Boil Water and Add Borax

In a separate pot on a cook surface or a kettle, heat water to a rolling boil. I pre-measured the water needed to fill my bowl and boiled it on the stove. Once the water is boiling, pour it into your bowl.

At this point, stir in about 1-1/2 cups of Borax. Add about half and stir until dissolved. Continue adding powder until the water becomes so saturated it stops dissolving and starts to accumulate at the bottom. The key to large, strong crystals is a super saturated solution. I'm probably not going to be using Borax anywhere besides this project, so I went fairly heavy handed on my solution.

Step 3: Cotton and Position

Take a handful of cotton balls, compress them into a matted clump, and place clump into hot solution. The cotton balls may want separate, but just use the chopsticks or a fork to reposition into a fixed cluster. It's good to go ahead and submerge the clump with the utensils and position it within the bowl.

Step 4: Cover and Wait

Go ahead and cover the bowl with something to trap the heat. I used a piece of foam I had lying around, but I have also used cardboard.

Next, we wait at least eight hours! Through the glass, I was able to see growth after just four hours! Then I let it sit overnight; totaling about 14 hours of soaking.

At this point it is good to mention the importance of a clean work area. The solution will crystalize wherever it lands. That includes, but is not limited to, the splashes that land on the table/countertop and under the bowl. While the crystals are not hard to remove (just water and abrasion) I would not want to risk scrubbing down the varnish of your work surface.

Step 5: Drain and Remove

After sitting overnight, you're almost finished!

Go ahead and drain the solution from the bowl. The hardest part of this project is removing your final product. The crystals will have formed in and around the cotton as well as along the bowl. Because the cotton is sitting on the bottom of the bowl it has probably crystalized to the surrounding bowl structure too. For my use, it was important to keep this bowl structure attached so I was being very careful in removing it as one piece. Grabbing the Cotton Crystal, gently twist to the left and right and soon the entire crystalized bowl will lift! If you're unconcerned with the bowl crystals, just break the cotton crystal away from the surrounding structure! And voila!

It is important to drain and thoroughly dry your Cotton Crystals on a rack before handing because the crystals will disintegrate with additional moisture.

If you want even more Cotton Crystals, pour your solution and any leftover crystals (minus the cotton) into a pot, bring to boil, and re-saturate the solution with more Borax for another round!

Step 6: Explore and Make!

Your Cotton Crystals are the physical product of a material phase change. When Borax is dissolved into boiling water, an abundance of crystal molecules are dispersed about the fast moving water molecules. By bringing the solution to its saturation point while it is hot, there will be an excess of solute (Borax) when the solvent (water) cools. As the solution cools, the water molecules slow down creating less room for the over-abundance of Borax molecules. The release of the excess solute results in the collection previously dissolved crystal molecules on surfaces -- in this case, cotton. If you're interested in knowing more about crystals and how they work, and both have great information!

Explore More!

This phase change happens with other crystal molecules too! Check out this great project on how to grow your own Salt Crystals!

Scaffolding - This project works great using pipe cleaners! Check out these other projects on how to make snowflakes or add lights to your Borax crystals! I'm going to try and find more ways of attaching to fluffy, furry, and fuzzy things! Let me know if you find anything else that works well!

Color - As you can see in my final closeup shots, I attempted to added some color! If you're wanting to add a subtle hue to your Cotton Crystals, just stir in food coloring to the hot solution. The color comes out very faint so add a lot for a brighter result. I mistakenly added my favorite Mixol #27 which is meant for resin and not water, so it did not dissolve into the solution.

More Borax - All that leftover Borax is good for cleaning, but also for other fun projects like slime! If you're concerned or just curious about Borax, here is a great op-ed thoroughly looking into the wonder cleaner.

Make sure to comment and share your projects! I am excited to see how all the Cotton Crystals turn out!

Be the First to Share


    • Tiny Speed Challenge

      Tiny Speed Challenge
    • Woodworking Contest

      Woodworking Contest
    • Trash to Treasure Contest

      Trash to Treasure Contest

    4 Discussions


    3 years ago

    it looked like rock candy at first. I probably should not try this one. My son eats everything. I even have a jar of glitter that is labeled "not food"


    Reply 3 years ago

    I'd argue glitter should be edible too! But as for the Cotton Crystals, Borax is not safe to consume. So maybe stick to crystalizing sugar!


    Reply 3 years ago

    I have edible glitter but my son was walking through the kitchen, found the glitter container, thought it was sanding sugar so the figured he could have a pinch. He then went yelling through the house about this being the worst stuff ever and did I know that it was not sugar. I pointed to the label. That was the beginning of him labeling things--usually by telling you what the thing is not.


    3 years ago

    That's neat :) I've only done this with sugar crystals before.