Growing Crystals

Grow your own sparkling crystals from simple ingredients!

About the experiment:

Discover the fascinating world of crystal formation. With patience and a few household ingredients, you can grow beautiful, glittering crystals. This experiment shows you how molecules combine into ordered structures under the right conditions.

Required materials:

• Hot water (distilled water works best)
• Alum powder (potassium aluminum sulfate, available at pharmacies or online) or alternatively sugar or salt
• A clean jar or glass
• A spoon for stirring
• A pencil or wooden stick
• A piece of string or pipe cleaner
• Optional: food coloring to grow colored crystals

Step-by-step instructions:

1. Heat the water (it should be hot but not boiling). Ask an adult for help.
2. Slowly add the alum powder (or sugar/salt) to the hot water and stir continuously until no more powder dissolves. You're creating a saturated solution.
3. If you want colored crystals, now add a few drops of food coloring and stir.
4. Let the solution cool down a bit.
5. Tie the string or pipe cleaner to the middle of the pencil. The pipe cleaner serves as a 'seed crystal' where crystals can grow.
6. Place the pencil across the opening of the jar so the string/pipe cleaner hangs into the solution without touching the bottom or sides of the jar.
7. Place the jar in a quiet place where it won't be disturbed. Avoid vibrations.
8. Observe over the next few days how crystals form and grow. It may take several days to a week before you see clear crystals.

The science behind it:

When you dissolve alum (or sugar/salt) in hot water, more particles of the substance can disperse in the water than would be the case with cold water. As the saturated solution cools, the water becomes 'supersaturated' – it contains more dissolved substance than it can hold at that temperature. The excess particles begin to attach to each other and to the seed crystal (string/pipe cleaner), forming regular, geometric structures – the crystals. This process is called crystallization.

Safety notes:

Wichtig: Hot water can cause burns; an adult should help with heating and pouring. Alum powder is generally safe but should not be swallowed. Wash your hands after the experiment.