You will need

• Short length of wool or string
• Warm water
• 2 Paperclips
• 1 Plate
• 1 Spoon
• 2 Glass jars
• Washing soda

What to do

1. Fill both jars with warm water. (From the tap is fine.)
2. Add washing soda to both jars and stir until no more washing soda dissolves.
3. Attach a paperclip to each end of the string or wool.
4. Place the ends of the string in the jars, so the string hangs between the jars.
5. Place a plate between the jars to catch the drips of the solution flowing along the string or wool.
6. Leave the jars for one to two weeks in a safe place and observe what happens.

Background

The washing soda solution slowly soaks the string or wool and flows along it. As the solution drips off some washing soda is deposited slowly forming a crystal.

Water flowing underground dissolves minerals when it seeps through rocks. The minerals are deposited when the water drips of a cave roof. A crystal is formed that hangs off the cave rood which we call “stalactite”. When the water drips to the floor it deposits minerals there forming a crystal growing up from the ground which we call “stalagmite”.

In your experiment a stalactite grows hanging from the string or wool.

You can watch a video of this experiment: