How to make crystal egg geodes (or diamonds in a lid) - Magical Daydream: grow your own crystal egg geode in an eggshell with alum, fun DIY, craft or science project for children. Including a free printable checklist in blogpost

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You know what is even more exciting than colourful gemstones, sparkling diamonds and beautiful geodes? Making your own! I read a number of different tutorials on how to make a crystal egg geode before trying it myself. Today I will share with you what I’ve learned from the experience.

1. You need alum powder. Alum is a type of salt. I found a block of alum in the drugstore. One of the uses of alum is to stop shaving wounds from bleeding. Apparently you can also use sugar or normal salt for this project. However, these will make your crystals cube-shaped instead of hexagon-shaped.
2. Because I bought a block of alum, I needed to crush it to make a fine-grained powder.
3. You need an egg. Different tutorials advice you to blow your egg out first. I tend to want to do things the quick and dirty way. So I skipped this time-consuming step and simply crushed my egg, hoping it would break in half the way I wanted. It did. Clean it and let it dry. Now apply white glue on the inside of your egg.
4. Sprinkle some of your alum powder over the wet glue until you covered the inside thoroughly. Let it dry for a couple of hours.
5. I repeated the glue and alum powder process for a small lid. I was curious to see if it would work just as well on a different surface. (It did.) I imagine you can be creative with what you let your crystals grow on.
6. Take some very hot water from the tap. Now try to dissolve as much alum powder in it as possible. Stir well. You don’t want to leave small undissolved parts on the bottom of your cup, otherwise crystals will start to form on them as well. I found that heating the solution in the microwave helped to dissolve the last bit of alum powder.
7. Add food colouring. Note that the crystals won’t actually absorb the colour. They only look a certain colour because the surface they are attached to does take the colour (like the egg shell).
8. Add your egg to the cup and carefully let it sink to the bottom (alum side up). I used two cups with different food colouring: one for my egg and one for my lid. Put it on a safe place and don’t touch it for a day or so. The time you have to wait to get the result you want may vary. In my case, after a day I still wasn’t quite content with the result. So I added some extra alum (heating it up again to dissolve) to the solution and waited another day. When your egg geode is ready, simply take it out and let it dry. The wet crystals can still be somewhat fragile, so be careful.

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I think this would make a great science project for kids, or just a fun project to experiment with yourself. You could take it a step further and add a sprinkle of kindness to this project. You could give it to someone with for example a little note saying ‘you are a gem’ (alternatives ideas for texts: ‘diamond in the rough’, ‘shine bright like a diamond’, ‘a sparkle to make your day’). After all, who doesn’t like colourful sparkling things with kind messages?

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39 Comments

  • Reply

    RaChil Luke

    March 19, 2014 at 22:03

    I loved making these as a kid, mine never turned out as pretty as yours though! I think that is because of the alum, I’ll have to find some of that and get to playing! :) Thanks for sharing!

    • Reply

      magicaldaydream

      March 20, 2014 at 13:32

      Well, I am not sure how different the effect is with sugar/salt. I definitely think the fact that I kept it in for 2 days also helped.

      • Reply

        RaChil Luke

        June 11, 2014 at 14:04

        I got my hands on some Alum Salt and ended up making some crystal necklaces! Thank you for the inspiration :) I made a tutorial for them if you’d like to see :)

  • Reply

    Carly

    March 19, 2014 at 22:31

    I’ve always wanted to know how to do this, but I never got to looking it up. It sounds pretty easy after all! Thank you for the tutorial, and I’ll think I’ll have to try it soon!

    • Reply

      magicaldaydream

      March 20, 2014 at 13:31

      I never knew these excited until 2 weeks ago.. I feel like I missed something in my childhood ;) :p

  • Reply

    bekswhoknits

    March 20, 2014 at 01:26

    I’ve never seen these before but they’re awesome!!!!

  • Reply

    RaChil Luke

    April 3, 2014 at 17:34

    What kind of glue did you use? Just regular white glue?

    • Reply

      magicaldaydream

      April 14, 2014 at 14:03

      Yes! Just regular white glue. Most instructions said that, so I just followed the advice :)

  • Reply

    Moondragon007

    June 5, 2014 at 02:40

    I wonder what would happen if you mixed salt/sugar with the alum?

  • Reply

    louisiana

    June 6, 2014 at 07:27

    if i make them with salt, would it work properly?

    • Reply

      magicaldaydream

      June 10, 2014 at 17:35

      I believe that the main difference is that you will get ‘cubic shapes (4 corners)’ in stead of the ones with alum that have 6 corners. But I haven’t tried personally, so I would just give it a go and see what happens!

  • Reply

    Katie

    July 23, 2014 at 03:58

    Thanks for the tips and instructions! I am planning on doing this with some third graders. Which type/brand of alum powder did you use? Do you recommend a specific brand that worked best?

    • Reply

      magicaldaydream

      July 23, 2014 at 08:28

      I can’t remember the brand with certainty. I live in the Netherlands and I believe it was a brand from a local drugstore (and the only one I could find in the store). So I don’t think it really matters what type you use. Hope this helps. And good luck with the children, sounds like a great experiment to do with them :)

  • Reply

    RaspberryT

    July 25, 2014 at 05:56

    May I ask how much food coloring did you use? Have you tried any other types of dye? Would you know if they work better or not?

    To answer about the type of alum you should use, it is recommended that you use an alum that has “Potassium Aluminum Sulfate.”

    You have to make sure you get the right kind of alum powder, potassium aluminum sulfate. Some commercial alum contains potassium, and some don’t. If you get the kind without potassium, your crystals will not grow.

    • Reply

      magicaldaydream

      July 25, 2014 at 14:25

      I only used a few drops maximum. You don’t need that much. I haven’t tried any other dye but I think they should work as well. The main thing is that they should be able to somehow get ‘stuck’ to your egg shell, as they don’t merge with the crystals themselves. And thanks for the extra info, I didn’t know that. But I guess I got the right type because mine seemed to work ;)

  • Reply

    RaspberryT

    July 25, 2014 at 12:11

    Wow, your geodes came out really, really nice. The crystals are very clear, good color, and large. I haven’t seen large crystal results anywhere on the internet like yours. I’m glad I came across this site. Thanks for the instructions. It’ll really help when I do this experiment with my son & his nephews.

    • Reply

      magicaldaydream

      July 25, 2014 at 14:27

      Sounds fun! Let me know if everything worked out! I love seeing end results of people who try something using my DIY’s! :)

      • Reply

        RaspberryT

        August 13, 2014 at 15:19

        End Results:
        Our experiment turned out really well. Some of the crystal formed from our egg shells were really large, like yours, and others were really small. I believe the reason for this result is because of the cooling time & space. We dropped the egg shells in the mixing liquid when it was still very hot while others, we let it cool down before dropping the egg shells in. The hotter liquid mix resulted in larger crystals. Also I should note that I left a good amount of the mixing liquid in the original container with lots of space for crystals to grow & the crystals formed in that were very large half Octahedron crystals and just plain clear color. It was the coolest ones.

        Thanks again for the instructions. On another note, I don’t’ think the amount of any food coloring will effect the growth of the crystals. Just the amount of potassium alum sulfate you use.

        • Reply

          magicaldaydream

          August 20, 2014 at 20:19

          Awesome! And the hot/cold is a good tip. I didn’t know it made a difference, I just put it in there while the water was still hot. Did you make any pictures?

          • Dalia

            December 19, 2014 at 10:34

            How long did it take for Them to grow that much?

          • magicaldaydream

            December 25, 2014 at 12:48

            About 2 days (check out step 8)

  • Reply

    Aline - Inspiré et Créé

    November 15, 2014 at 21:12

    Waoh, the resultats are very wonderful, i totally love it!
    Thanks a lot for this tutorial, i will test it for sure!

  • Reply

    James

    February 28, 2015 at 18:25

    As stated, if dropped in warmer water, the crytals are larger… has anyone tried boiling the water, then dropping shell in? Would this increase the crystal size?

    • Reply

      magicaldaydream

      March 23, 2015 at 08:14

      Increasing the temperature has the main effect of being able to dissolve more salt in the water, so therefore boiled water would dissolve the most salt en will probably get you larger crystals/quicker.

  • Reply

    James

    February 28, 2015 at 18:33

    How much alum was added to water? And did you leave alum dust on shell, or removed excess?

    • Reply

      magicaldaydream

      March 23, 2015 at 08:15

      Can’t remember exactly, I think about 2 full spoons? I did leave the alum dust on the shell.

  • Reply

    Michelle

    April 29, 2015 at 05:46

    Hi thanks for the diy!! I was wondering if we could reuse the solutions and if you knew how to prevent from getting crystals at the bottom of my containers and floating above my solutions. I have made egg geodes 5 times now and every single one has came out like that. I make sure to dissolve all the alum powder by putting it in the microwave, but not only that, I also strain the water of any excess alum powder; yet, I’m still getting crystals forming at the bottom of my containers and floating above the water.

    • Reply

      magicaldaydream

      May 6, 2015 at 15:09

      I also got extra crystals in the bottom I don’t think you can really prevent that from happening. In essence you can reuse the solutions. But you need to remember thata lot of salt has already been used up from it, so you will probably need to add more alum again to get the same results.

  • Reply

    Lily

    July 22, 2015 at 08:12

    I was wondering, could you do this with epsom salts. I’ve read some sites saying that you could use those, and if you could use epsom salts would you do the same process or something different.
    Thanks for this cool post, it also really helped that you mentioned that you could grow crystals on lids because I have tons of spare ones!!!
    Thanks for your help ;) and the awesome diy.

    • Reply

      magicaldaydream

      July 22, 2015 at 10:54

      I’m sorry, but I have no idea. I never worked with epsom salts myself and can only talk about my experience.. But perhaps I can try it and blog about it in the future ;)

  • Reply

    tiff

    November 10, 2015 at 01:30

    wow! that is so cool. How did you get the red color on the lid?

    • Reply

      magicaldaydream

      November 11, 2015 at 14:25

      Like I say in step #7: Add red food colouring to the water.

  • Reply

    Cindy

    December 14, 2015 at 12:46

    I have one question. What happens to your crystals if they get wet? Do they dissolve?

    • Reply

      magicaldaydream

      December 14, 2015 at 14:25

      Well, they won’t dissolve with the first splash of water, but they’re made of salt so I’m pretty sure they will dissolve eventually, especially in warm water. I heard that water mainly makes them a bit more fragile. So I wouldn’t put them in a bowl of water. But I have dipped mine in water and directly out again to clean them and that was no problem.

  • Reply

    Lily Ardor

    June 23, 2017 at 20:27

    OH my Gosh.. this is so AWESOME. I had no Idea you can make these. They look so expensive. :D :D

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