You will need:

  • Bicarbonate of soda
  • Two glasses or glass jars
  • Wool
  • Boiled water
  • Side plate
  • Spoon

What to do:

  • Make a solution of bicarb and boiled water (7tsp per 250ml of water). Add one teaspoon at a time, stirring to dissolve
  • Drape a piece of wool between the glasses, making sure the tail in each glass touches the bottom of the glass
  • Place a side plate beneath the lowest point of the wool to catch drips
  • Watch crystals grow along the wool