How to Grow Alum Crystals

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How to Grow Alum Crystals

Ever thought of growing alum crystals at home? The following article provides information regarding the method of growing beautiful alum crystals.

Chemically, alum is a hydrated aluminum potassium sulfate that possesses a specific crystal shape. It is non-toxic, dissolves easily in water, and reacts with various acids. You can find several types of this salt in the market like potassium alum, soda alum, ammonium alum, and aluminum alum. It is mainly used in water treatment methods to reduce its turbidity. It is also used in culinary applications, medicinal field, and cosmetic products.


Purchase alum (2½ – 3 oz.) from your nearby grocery store. Other required supplies are ½ cup water, sewing thread or string (preferably nylon fishing line), shallow dish, clean glass jar, spoon, pencil, and absorbent paper towel. Once you are ready with these materials, refer to the following tips:

  • In a saucepan, pour water and put it over a furnace burner. Bring it to a boiling temperature; remove from the heat and carefully, pour it into a glass bowl.
  • In this bowl, add alum in small amounts, while stirring constantly. Continue to stir until it no longer dissolves in the solution.
  • You can stop adding alum, when it starts to settle at the bottom of the bowl. This is known as the saturation point.
  • To make a seed crystal, pour a small amount of this saturated solution in a shallow dish. Add the remaining solution to a clean glass jar, and keep it aside. You will use this jar to grow large alum crystals. When the solution in the dish cools down, you can notice the formation of small crystals.
  • Now, isolate an evenly shaped alum crystal from the dish, and allow it to dry completely. This crystal is referred to as a seed crystal, which you will be using as a base to grow a larger sized alum crystal.
  • After the seed crystal is dried properly, tie one end of the nylon fishing line around it, ensuring that the crystal will not fall down. Take the remaining end of the nylon line, and tie it on a pencil or a ruler, on the middle portion.
  • Hang the seed crystal in the jar containing alum solution, by placing the pencil on top of the jar. If necessary, adjust the length of the nylon line so that the crystal is suspended freely in the solution, without touching the sides and bottom of the jar.
  • Cover it with a paper towel, and keep it in a cool place. Do not disturb it for several days, and you will see large alum crystal growing in it.

The most amazing part is that, you can carry out this experiment by using easily available supplies, which is not the case for other science projects. You can add varying amounts of a specific food coloring agent to make beautiful colored crystals. Also, try growing them by using different colors like red, green violet, etc., and arrange them to create your own alum garden.

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