How to Make Egg Geodes

Today we’re experimenting with egg geodes and I’m going to share how to make egg geodes with borax.

This experiment is set up to engage children in the steps of the scientific method, which could easily make this a fun and successful science fair project (<–see this list for science fair project ideas)

Not only is the process of making these beautiful geodes engaging for kids, but the end-result has a huge wow-factor. Give yourself at least two-three days to achieve the greatest results.How to make egg geodes

Egg Geodes Inspiration

I was inspired by these egg geodes that I spotted on Martha Stewart and then followed this recipe by Melissa Howard who blogs at Those Northern Skies. If you enjoy this post, do click over and see what these two sites have to offer. The pictures alone are worth looking at.

How to make egg geodes.



  • Eggs
  • Rock Salt
  • Sea Salt
  • Borax*
  • Other substance that could be tested for crystallization such as sugar, epsom salts, cream of tartar, baking soda, or alum*
  • Mini-muffin pan
  • Food Coloring
* Borax and alum are not food products, and using these ingredients with small children should be closely monitored, as ingestion can be fatal. Please use common sense and close supervision with such substances. My children were watched at all times and did not come in direct contact with borax in the process of this experiment.

How to make egg geodes

I tapped a knife around the top of the eggs to remove a bit of shell, and then emptied the eggs and cleaned them with water. Using a finger, it’s important to gently rub around the inside of the egg to remove the membrane because the membrane can discolor crystals as the form.

If you happen to have a mini-cupcake pan, it’s like they were made for this job.

How to make egg geodes.

We heated a pot of water (not quite boiling) and then poured 1/2 cup into a mug. We added 1/4 cup of kosher salt into the first mug and mixed it until it dissolved.

The kosher salt was stubborn and wouldn’t dissolve, so Nutmeg handed the mug to me for some rigorous mixing. Sill no luck.

We moved on to the next mug: 1/2 cup hot water + 1/4 cup sea salt. The sea salt dissolved quickly and then we added a bit more. The idea is to saturate the solution without putting in too much of the dry ingredient.

And then the final mug: 1/2 cup hot water + 1/4 cup borax. Dissolved.

How to make egg geodes.

We added a coup;le drops of food coloring to each mug and then made a chart so we wouldn’t lose track.

Then we poured the liquid into our eggs. Each solution made just enough to pour into two eggs. Perfect!

And then you wait. 5  days for the liquid to mostly evaporate.

We couldn’t that long, but after 1 day salt crystals evaporated through the egg shell, and after 2 days our eggs looked like this…

How to make egg geodes.

How to make egg geodes with borax and salt.

Kosher Salt 

Through the process of diffusion, the salt actually passed through the permeable shell. Gorgeous, isn’t it?

How to make egg geodes.

Sea Salt

How to make egg geodes with borax.

With opposite results of the salt-solutions, borax created the most sparkly, crystal-looking egg with crystals inside the egg and nothing on the outside.

And of course, things like this are irresistible to little hands. My toddler wanted to pick all the crystals off the shells, and I had to pull them away because not only will she break them into a gazillion pieces, but substances like borax are safe for looking, not for touching.

So, if this strikes your fancy, have fun testing some of the different soluble solids mentioned in the list above.

How to make an egg geode with salt and borax.


    • Love that you’re doing it! Yay! Please report back and send me a photo! radoorley at gmail.com

  1. This looks like a great idea and I will definitely be trying this, thank you. I am concerned with your little girl touching the borax crystals though.
    Everyone should be aware that borax is toxic and can result in adverse symptoms. Some of the symptoms of Borax ingestion include headache, fever, nausea, vomiting, and red eyes. People should be very careful about their small children handling water soluble borax by making sure that they wash it off quickly .

    Symptoms may appear 2 to 4 hours after ingesting Borax.

    The best way is to never eat Borax and never use it in food.

    • Thanks for the shout out for caution, Sue! Because we use these substances with close supervision I sometimes forget that other people may not know about these things. In the photo above, my little one is handling the kosher salt crystals. I made a correction to the post that I hope clears this up for concerned readers. Cheers!

    • Thanks for the shout out for caution, Sue! Because we use these substances with close supervision I sometimes forget that other people may not know about these things. In the photo above, my little one is handling the kosher salt crystals. I made a correction to the post that I hope clears this up for concerned readers. Cheers!

        • Thanks for the nice comment, Daina 😉

  2. These are really beautiful! I know my daughter would love this. Thanks for the great tutorial.

    • Thanks, Melissa. You’re a great partner-in-crime.

  3. These are really beautiful! I know my daughter would love this. Thanks for the great tutorial.

  4. How am I only now hearing about this fun with eggs?!? My kiddos love anything that involves eggs! I have used them for quite a few different “experiments”, who knew you could so much with them?! I will definitely be doing this one.. and now I’m off to read about all of the other ‘eggtivities’ you’ve done so I can do those too! Thanks 🙂

    • Who knew? And to think that we had to stop ourselves with just 10 egg projects! But guess what, I’ve been collecting egg ideas from my blogging friends, and will have even more for you next week 🙂

    • This is right up your alley, Amy!

  5. So cool!  I am just loving all the ideas you and Melissa are sharing this week!

    • We’re having a lot of fun, that’s for sure!

  6. I love visiting both of your blogs to look for great ideas. Thanks!

    • Thanks so much, Natalie! So glad that you’re here.

  7. Now, where to find Borax?  But not sure yet if we’ll do this!  My little one is a riot and I doubt I can control his excitement and NOT let him get his hands on the finished product!

    from LPN Programs

    • Hee hee. I found it in the laundry aisle at Target. It comes in a powder form, and looks kind of like a box of Tide or similar laundry soap. 

  8. We tried this experiment with salt, borax, sugar and Washing Soda on our blog http://raisingourfamily.blogspot.ca/2012/04/egg-experiments.html the Washing soda had the best results for us.  Thank you so much for the awesome experiments.  We are off to go do more!

  9. I am doing the experiment for school and I how much alum would I use. Also what is the topic of this project like what are we trying to find out?

    • Hi David, We didn’t run the experiment with alum or epsom salt (per your question below), but if you do a search on alum/epsom salt + egg +geodes, I bet something will come up. You could run the experiment with different amounts of each substance and compare the results. Good luck!!

  10. Oh and how much epson salt do I use?

  11. i’m useing this for my sci. project. i hope it works!!

    • Hi Anna,
      I’m sure you’ll love it. It’s such an interesting process and you’ll learn a lot, first hand, about diffusion. Not to mention, the results can be stunning.

      • i used sugar, water(control), and sea salt. The results are quite cool. i hope i get an a on it.

  12. Hi! My daughter was considering doing this as her science fair experiment but we are having a hard time coming up with the actual question. Any suggestions? Thanks!

    • Are Egg Shells permeable? (These could lead to a discussion on Salmonella and if it is on the surface of eggs or also on the inside.)

  13. My son and I found this experiment just two days before Easter and are so excited about it. We used kosher salt, sea salt and sugar. So far the kosher salt is doing well I am excited to see how the sugar turns out but those crystals usually take longer. Thanks so much for this fun activity!

  14. Looks like a fun take on the Geode. Great science fun for the kiddies.

  15. Hi, thanks for the really cool idea! You discussed what happens after 5 days, but I wonder what happens if they are left undisturbed for weeks? Do they mold or continue to crystalize? We are planning to use this as a science experiment for my daughter and we are just trying to figure out the timing of it!

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  18. This is SO. COOL.! I would love to link to your project in my next Kids Craft Roundup if you didn’t mind.

    • ours was a fail for the scinece faie0

  19. […] My youngest daughter was intrigued with the idea of creating egg geodes by growing crystals inside of clean-out egg shells. She experimented with solutions made from borax, sea salt, and kosher salt, and each one produced a unique result. Inspiration found at: Egg Geodes at Tinkerlab […]

  20. thank you for the tips i really needed it for my science fair project. 🙂 🙂 🙂 🙂

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