How to Grow Crystals

Some of the largest natural crystals ever found are in the Cueva de los Cristales (Cave of Crystals) in Mexico. Some of these fabulous crystals are 36 feet long and can weigh as much as 55 tons. Formed from gypsum, they are transparent and glitter like a cave full of massive diamonds. Although you probably will not be able to grow crystals as large as those found in the Cave of Crystals, it is easy to grow a variety of crystals gardens at home with common household ingredients. Parental supervision is recommended since some ingredients are toxic.

 One favorite recipe is made with salt and ammonia. Here’s how.


Charcoal Briquettes (or pieces of sponge or brick or porous rock, this will be your substrate)

Distilled Water

Uniodized Salt


Mrs. Stewart Bluing (find it in the laundry isle at the grocery store or you can order it online at

Food Coloring (one or more colors of your choice)

Non-Metal Pie Plate (glass is great)

Measuring Spoons

Empty Jar

A plastic disposable spoon

Break or cut up your substrate into pieces about 1-inch in diameter. If your substrate is a porous rock, you will need to carefully break it up with a hammer.

Spread the broken pieces in an even layer in the pie plate.

Sprinkle the distilled water over the substrate so that it is thoroughly damp, pour off any excess water.

In the empty jar, mix 3 tablespoons uniodized salt, 3 tablespoons ammonia, and 6 tablespoons bluing. Stir well with the disposable spoon until the salt is dissolved.

Pour the water mixture over the substrate. You may need to add a bit of water to the jar and swirl it around to pick up the residual chemicals and then pour it over the substrate.

Sprinkle drops of food coloring, whatever colors you choose, here and there across the substrate. Where you don’t sprinkle food coloring the crystals will be white.

Sprinkle about 2 more tablespoons of uniodized salt across the substrate and set it in an area where it will not be disturbed for two days.

On the second and third day carefully pour a mixture of 2 tablespoons each of water, ammonia and bluing into the bottom of the pan, being careful not to pour it over the substrate which will disturb the crystals that are growing.

Leave it in the place where it will not be disturbed and watch it grow.

When you take it to your science fair, move it carefully, the crystals are very fragile. You can experiment with different ingredients and grow crystals that resemble priceless gems.

Another crystal garden is edible and one that you can grow to sell at your science fair. A rock candy garden is a great fund raiser to help support your school. It’s quick to make, it takes only about 10 minutes, easy and fun. Younger children will need adult supervision since you need to use a stove. Here’s how.


4 cups sugar

1 cup water

Food coloring

Clean glass jar

String, cut into 6-inch lengths


In a medium saucepan, heat 2 cups of the sugar and the water. Do not boil! Stir until the sugar is completely dissolved.

Gradually add a few drops of the food coloring of your choice and the additional sugar, stirring continuously until all the sugar is dissolved.

Pour the solution into a clean glass jar and tie the pieces of string to the pencil and suspend them across the mouth of the jar so that the ends hang into the sugar water.

Crystals suitable to eat will form in an hour and continue for several days to a week.

Although you may see quick results in small measure, the larger rock candy crystals you’re accustomed to seeing in the candy store will take some time to form. Pieces can be broken off and eaten after the first hour but the longer they remain the bigger they will become.

Yield: 12 ounces