Doktor Kaboom: fun science with Easter leftovers!


by New Day Producers

Posted on April 1, 2013 at 11:00 AM

Updated Monday, Apr 1 at 12:13 PM

Doktor Kaboom's website:

Doktor Kaboom's Easter Geodes

Here's a fun project to do with hard boiled eggs leftover from Easter, or your Passover Seder!



Leftover hard boiled eggs.

sharp knife and small spoon

all purpose white glue

small paint brush

¾ cup of alum, found in the spice section of your local grocery

2 cups very hot water

plastic or glass beaker, or jar



1. Carefully cut a leftover, hard boiled, egg in half, using a sharp knife. A steak knife works well. Use a small spoon to carefully scoop the egg out of the shell. Set aside to eat, yum! Then make sure the inside of the eggshell is clean and dry.

2. Using a small paintbrush, apply white glue (NOT washable glue) to the inside of the eggshell and sprinkle with alum powder until completely coated. Pour off the excess alum, and save. Set eggshell halves aside to dry overnight.

3. The next day, prepare your growing solution in a glass or plastic container by using a craft stick or spoon to mix 2 cups of very hot water (almost boiling). Add 3/4 cup of alum powder to the water, and stir until completely dissolved. If there are remaining crystals in the bottom of the container, place the solution in the microwave for a few minutes to dissolve them. This will prevent alum from being drawn away from the geode.

5. Add about 30 drops of food coloring to the solution. Once the alum is completely dissolved, let the solution cool slightly (for about 30 minutes) and then submerge one of the dried, alum-coated eggshells in the growing solution, allowing it to rest on the bottom of the container with the inside of the shell facing up.

6. Set the container aside in a safe place overnight to allow the crystals to grow undisturbed. (Tip: The longer the eggshell is in the solution, the larger the crystals in the geode will be. Twelve to 15 hours will usually result in a perfect geode.)

7. The next day, remove the geode from the growing solution very carefully (as wet crystals are quite fragile). (Tip: If you are not satisfied with the size of your geode crystals, return the geode to the growing solution and wait a day or two. As water evaporates from the solution, more alum will be deposited in your geode, increasing the size of the crystals.)

8. Place your geode on a drying rack or newspaper and allow to dry completely before handling.

9. To grow a second geode in the other half of the eggshell, simply re-dissolve the crystals remaining at the bottom of the growing solution in the microwave and start again.

Trying to make a lot of different colors can get pretty expensive, as you have to buy a lot of alum. You can get the same effect trying other ingredients, which can also be fun to experiment with. Try Borax, Cream of Tarter, or sugar, and see what kind of results you get!