How To Grow A Geode In an Egg

Want to make some amazing looking geodes grow out of an egg, and teach your kids some science at the same time?  It’s actually pretty easy, and the whole process takes under two days, most of that which is just watching and waiting. My daughter used this idea for her science project, too!

This idea comes from Martha Stewart, whose guest on her show, Dr. Figgy, taught how to make geodes out of eggs.  His directions to make these use a decent of alum, and only make 1 egg, or two egg halves.  Which is fine if you’re Martha and have unlimited resources.  But for the average person, who wants to buy pounds and pounds of this stuff to grow a handful of eggs?  Not me!

So I’ve streamlined the process, and came up with a way to make 6 geode egg halves instead of just 2, and without buying more ingredients!  And I’ll show you the ingredients to use in order to successfully grow your own geodes.  Interested?  Here’s what I did…

  • Alum (see note below for more details on what to buy)
  • 3 eggs
  • White glue (Elmer’s works great, or any other white glue is fine)
  • Paintbrush
  • 6 small glass jars (I used small mason jelly jars)
  • Food coloring
  • Newspaper
** Note:  It is important to buy the right kind of alum for this project!  You must buy alum that is “potassium aluminum sulfate.” If it is not potassium aluminum sulfate, the crystals will NOT grow. Some alum from grocery stores includes fillers, and the crystals will not grow.  
I used McCormick alum from the grocery store (it took 4 of the small jars), and it worked great!  You can also buy alum from Amazon if you can’t find it locally, just make sure that it is potassium aluminum sulfate, not just aluminum sulfate.


1.  There are two ways to open up your eggs.  You can crack them like you usually do to make scrambled eggs (easy).  Or you can do what I did, which is still easy, but takes a few extra minutes.  I poked a hole in the top and bottom of each egg.  I used a scrap booking tool that I had to do this, but a small knife or scissors would also work.  I wiggled the long skinny tool inside to break up the yolk, but you can use anything skinny and long, like a paperclip that is pulled straight.  I used a baby aspirator to push out the insides of the eggs out the bottom of each egg, and then used some small scrapbook scissors to cut the eggs vertically.  Your choice as to which method you use!  Next time I would probably just do it the easy and quick way :)

2.  Rinse out your eggs with some warm water, and use your fingers to remove the inside membrane from the shell, and let dry.  Use a paintbrush to paint white glue all over the inside and top of the eggs.  Generously sprinkle alum all over the glue, and let the egg shells sit out overnight to dry.  I used one small jar of McCormick’s alum for this step. Make sure you wait til the next day to do the next step.

3.  This is where my directions differ from Martha’s.  You’ll need two cups of VERY hot water (almost boiling).  My tap water gets really hot, so I just used that, but you may need to heat yours up depending on the temperature your water is set to.  Add 3/4 cup of alum to the hot water, and continue stirring until the alum is completely dissolved.  For me, 3/4 cup of alum was exactly three small jars of McCormick’s alum- perfect!  It is important that the crystals are completely dissolved!  If they do not dissolve after stirring, then place in the microwave for a minute at a time, to dissolve the alum.

4.  Once the crystals are completely dissolved, pour the mixture evenly into six small jars (see my photo).  The small mason jelly jars I used were the perfect size!  Add about 20-30 drops of food coloring to each jar, and stir the color in with a plastic spoon.  Feel free to mix colors!

5.  Let the mixture cool in the jars for about 15 minutes, and then carefully add one egg half to each jar, making sure that the egg half is completely covered by the colored alum mixture.  Let the eggs sit untouched for 12-24 hours.  You can carefully check an egg after 12 hours, and if you want larger crystals, then place the egg back in the solution for longer.  When your crystals are your preferred size, then carefully pull the egg halves out of the jars, and let them dry.

Now you have your own beautiful geode eggs!  I love that this project is pretty easy to do, but you can get such amazing results!!  If you would like to read the scientific explanation of what is happening, then you can read more about it here, at the bottom of the post.

My kids were very impressed with our geodes, and are already wanting to make another set of them.  And I just so happened to have bought an extra set of alum, so next week we’re going to make these again, but with different colors.  These eggs would look really cool with the neon food coloring they have now too!  Hmmmm….. might need to try that now, too.

If you make these, let me know how they go!  It’s pretty exciting to watch a broken eggshell transform into something so beautiful!

Speaking of beautiful eggs, you can easily make beautiful marbled Easter eggs that can be kept from year to year.

I still have some from a set I made more than 10 years ago!  Here’s the tutorial with step by step photos to follow.  My kids love to help me make these!

If you happen to break some of your lovely marbled eggs (like my son did), then you can also make these pretty marbled Easter egg candles!

Another fun Easter craft to do with the kids are these fun Peeps pops, which come with free printable tags and are perfect for passing out to friends!

xo, Laura

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  1. says

    I am so going to try this!! Do the eggs keep forever or do you need to throw them out after a while. My daughter gets so attached to crafts so I like to be able to go into it telling her what to expect. I’ll let you know how mine turn out!

    • says

      This is my first year making these, so I’m not sure how long they will last. Alum is used to pickle vegetables, so I think that it helps to preserve them too, so I’m guessing these will last for a while, but I’m curious as to how long too! I’ll update the post once I figure it out :) Yes, be sure to come back and let me know how it goes, good luck!

    • says

      Good question… You would have to have a big enough hole at the top to have enough room to paint the glue on the entire inside surface of the egg, and then sprinkle the alum in. The geodes grow as the solution starts to evaporate, so I don’t know that the liquid would evaporate as well in a whole egg.

      You could always give it a try and see how it goes. If you try it, be sure to come back and let us know how it goes! I would still leave a decent enough hole, but just leave more shell on. Good luck!!


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