Alum can be found in the spice aisle at the grocery store. It is generally used for pickling vegetables. [2] X Research source Alum is nontoxic, but can cause irritation to the eyes. Avoid touching your eyes or wear protective glasses. [3] X Research source Glass jars are recommended because you will be using hot water. Also, it is easier to see the crystals form. The pencil needs to be long enough to sit on top of the jar.
Add a cup of hot water to one jar. Stir in a tablespoon of alum until it dissolves. Keep adding alum and stirring until the alum no longer dissolves. You may see a small amount of alum powder at the bottom of the jar. Add food coloring at this stage to color the water.
In order to grow good crystals, you don’t want any particles in the solution. Wash the original jar, you will use it again later for the second stage of growing.
For a strong seal, wrap a rubber band around the plastic wrap or foil.
You can leave the jar for longer, but if you have crystals at the bottom, you can use these as seeds to grow larger crystals.
You can also add another spoonful of alum to the jar to replace the alum that formed into crystals.
You may notice that some of the crystals are overlapping. These will not work well to grow larger crystals. Choose a single crystal to use as a seed.
Clear string is recommended because the crystal will grow around it. Darker colors will be seen in the crystal. Tie the other end of the string around a pencil or popsicle stick. Use caution if you choose to use superglue to attach the string.
If you didn’t already, you can add more alum to the solution to replace what formed into crystals during the seed formation stage. Make sure the solution is cooled to room temperature before placing the seed crystal into it. If the water is warm, it will dissolve. [9] X Research source
You can make a tighter seal by placing a rubber band around the plastic wrap or foil.
Keep the crystal in a cool place so it doesn’t dissolve. After a few days, check on the crystal. You can tell how much it has grown by the location of the clear string within the crystal.
Remove the crystal, add a spoonful of alum and stir until dissolved. Replace the crystal and let it grow for a few more days. You can repeat this process until your crystal is at the desired size.
Try making crystals of different sizes and colors. If you do accidentally get your finished crystal wet, quickly take a paper towel or a cloth and pat dry until the water is mostly dry. It might dissolve, but it won’t dissolve as much.
The eggshells need to be cut in half widthwise, washed out, and dried before use. The food coloring is optional, but it allows you to color the crystals of the geode. The glass container needs to be large enough for the eggshell to be completely immersed in water.
Don’t let the glue dry between this step and the next.
If you want larger crystals, lightly sprinkle the alum making sure there is some space between the powder granules. Leave the eggshell to dry overnight.
Add food coloring to change the color of the geode. Cool the solution to room temperature.
Cover the top of the container with plastic wrap or foil to keep dust out.
Store the experiment in a place where it will not be bumped. If it gets bumped or moved around, the crystals will not form properly. Once you remove the eggshell from the solution, you will have made an alum crystal geode!
