Growing crystals is easy. Learning chemistry becomes easy and fun when you allow children to make crystals with sugar, salt, and alum at home. Rock candy crystals are more popular among children. Before we dwell into the subject let's make the basics of crystals clear.

What are Crystals?

A crystal can be defined as a substance that has a distinct internal structure. The atoms of a crystal are arranged in a lattice pattern. The most common crystals available in every home are salt and sugar. The precious gemstones such as diamonds, rubies, and emeralds are also crystals. An interesting feature of crystals is they can be shaped and polished. Nucleation is the process by which a crystal grows.

Recipes for Homemade Crystals

Crystals can be grown at home using the chemicals available in any departmental store. Try the following instructions to grow crystals.
  • Sugar Crystals
To make sugar crystals you would need 3 cups of sugar, 1 cup of water and food color (optional).

Boil 1 cup water with 3 cups of sugar. Stir continuously till the sugar has dissolved.
Add food color and mix well.
Sieve the sugar solution into a clean container. (The reason is undissolved sugar provides a surface for the crystals to grow and the crystals will grow in the container)
Suspend a wooden spoon or a skewer into the solution.
The solution should not be disturbed for a few hours.

On cooling, the solution will harden to form sugar crystals or rock candy. It is commonly known as rock candy because it resembles the rock crystals and the children would love to eat them.
  • Alum Crystals
You require ½ cup water, 2-1/2 tbsp alum, 2 jars, nylon threads.

Boil ½ cup water and pour it into a clean jar.
Add alum and stir well until no more will dissolve.
Cover the jar with paper towel and leave it undisturbed overnight.
Next day, pour the liquid from the original jar into another clean jar. Be careful not to allow any crystals into the new jar.
Select a good crystal from the original jar and tie it with a nylon thread.
Hang this crystal in the second jar without touching the bottom or the sides of the container. However, the liquid must cover the crystal.
You can see the crystal growing in the second jar. Allow it to grow till it stops growing.
Once the crystal stops growing, remove it from the jar and allow it to dry.

Seed crystals are grown if you are planning to grow a large single crystal. There are two methods to obtain seed crystals. In the first method, you can pour a small amount of the saturated solution, of any chemical, onto a plate and allow it to evaporate. The crystals that are formed can be scraped from the plate and used as seeds. In the second method, the saturated solution, of any chemical, is poured into a clean and smooth jar, probably a glass jar. Suspend a wooden skewer or a nylon thread into the solution. When the solution is left un-disturbed, small crystals can be seen growing on the string. These can be used as seed crystals. If a saturated solution of any chemical is poured on top of a rock, sponge or a brick, it crystallizes to form a crystal garden.

There are times when crystals do not form. The three main reasons are the impurity, unsaturated solution and undissolved chemical materials. Some of the remedies are to use clean containers, pure water and also use less impure chemicals. If the solution is unsaturated you can try crystallizing the solution by refrigerating it and reducing the temperature of the solution. The only way to remove the undissolved chemical materials is by filtering the solution to another clean jar.

The school children can try out the recipes of growing crystals at home with the help of the elders.The sugar or alum can be substituted with salt or copper sulfate. Allowing children to experiment at home would make learning science fun and easy.