This is a quick and easy science birthday party activity. Your birthday guests will be involved in the setup of the experiment which they’ll take home and enjoy for days as their “geodes” grow. This experiment can be tweaked to fit many birthday themes and the materials are reasonably inexpensive and readily available.

Naturally occurring geodes are hollow rock formations which contain deposits of crystals. Supposing you do not have a geological time frame at your disposal to acquire a geode and do not want to purchase some sort of geode kit, it's simple to create your own crystal geode utilizing alum, food coloring, an eggshell and a few other household items.

This experiment will involve eggs so be sure to inquire ahead of time if any guests have egg allergies. 


Treat your birthday guests to  fun activity they can take home and enjoy.



Food coloring - this is optional but the addition of color can be fun! I suggest having several colors available if possible.


Measuring cup

Pot in which to boil water

Mixing spoon


White Elmer’s glue

Paper towels

An egg (thoroughly washed) for each guest plus a few extras. The guests will be putting their mouths on the eggs so make sure they are clean!

Thumbtacks for each guest

Disposable paper bowls


Alum powder - this can be found in the spice section of most grocery stores.

Take home containers with lids. You can usually find inexpensive containers with lids that seal tightly at a local dollar store. The container should hold at least six ounces of liquid and be big enough for half an eggshell to rest inside.

Sharpie marker

Eggshells for making geodes. The birthday guests get excited when blowing the egg from the shell.



First you will want to prepare your solution. You may want to do this ahead of guests arriving as an exciting science themed birthday party can get quite rambunctious.

Fill a pot with six cups of water and heat it on high until it boils.

Remove from heat and mix in 2 ½ cups of alum powder until it is dissolved. There may be some undissolved crystals in the bottom of the pot but this is alright. You will want to allow for this solution to cool for at least thirty minutes before using it with the guests.

It’s time to get this science birthday party started!

Now, at this stage is up to the parent or host to determine what level of messiness they are willing to endure. I’ll give you the messy version here and you can adjust as needed by prepping ahead of time to have a cleaner experience.

Have all your guests seated at a table that is free of clutter.

Set a paper bowl, 2 paper towels, and thumbtack in front of each guest. Take a moment and highlight to your guests to be careful with the thumbtacks.

Now for the fun part! Have each guest poke a hole in the narrow end of the egg with the thumbtack. They will need to work the thumbtack around in the hole to make sure they punch through the membrane of the egg. Have plenty of paper towels ready for cleanup and some extra eggs.

Next, everyone will need to punch a hole through the opposite end of the egg.

The guests will now blow through that hole while leaning over their paper bowl. Inform the guests that it may take a little effort to get the egg to start flowing from the shell. The contents of the egg will eventually flow through into the bowl. The excitement level in the room will certainly escalate and erupt into lots of “Gross!” and “Disgusting!” exclamations.

Now we need to cut the eggshells in half. The host may want to do this individually or provide scissors so each guest can do so on their own.

Once the eggshells are cut in half, each guest will need to gently wipe out the inside of their egg. Instruct them to clean out any liquid and membrane. Hopefully by this stage of the activity, each guest has a half of an eggshell that is still in decent shape.

Have the guests choose their best eggshell half. Now go to each guest and put a dab of glue in their shell. Instruct them to spread the glue evenly with their finger. We told you science was messy! They can wipe their finger on the paper towel.

Quickly come around with the alum powder and sprinkle a dusting on each eggshell and allow the glue to dry for a few moments while you move on to the final stage of the activity.

Place a take home container and lid in front of each guest.

Have each guest place their prepared eggshell inside the container.

Now come around to each guest with the cooled alum solution you prepared earlier. Use the ladle to cover each eggshell with the solution ensuring the eggshells are fully covered.

Allow each guest to select the color they want for their geode. The guests often really enjoy being able to customize the color of their geode so try to have several color options of possible. One drop of coloring in each take home container is plenty. The food coloring isn't going to add coloration to the crystals, nevertheless it does add color to the eggshell which in turn causes the crystals to look colored.

Each guest will need to securely put the lid on their container. Pass the Sharpie marker around so each guest can write their name on the lid. The host will want to insure the lids are on correctly.

Collect the cups and make sure the guests take them home when they leave. Instruct them to place the cup containing the solution and eggshell someplace where it will not be disturbed. Allow the crystals to cultivate overnight. They can remove their geode from the solution the next day and permit it to dry out. The remaining solution can be safely poured down the drain. The alum is actually a pickling spice, so although it is not precisely good for you to eat, it is not harmful either.

Keep your geode looking good by safeguarding it from high humidity, dust, and dirt. It is possible to keep it stored a paper towel or tissue paper or within a display case. Your birthday party guests will have a great memento to enjoy that they helped create at your birthday party!

A science birthday party can be messy but are always enjoyed by the birthday party guests.



This is a great experiment for almost any science themed birthday party. Geode related activities are obviously great for rock themed parties. You can use the eggs to talk about dinosaur eggs for dino parties, or the look of the crystals can easily be spun to simulate some kind of space rock. Mad scientist party? Growing your own geode is a perfect fit! Have fun enjoying science and Happy Birthday!