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How to Make Rock Candy

Learning about chemistry and crystals can be fun – and tasty – with this simple recipe.


  • Step 1: Prepare your string for seeding Cut your string so it is shorter than your jar. Tie one end to a weight, such as a paper clip or galvanized washer.
  • Step 2: Set your seeding string atop the jar Tie the other end of your string to a pencil or stick. Place it atop the jar so that the string hangs straight down without touching the bottom.
  • Step 3: Heat the water Heat water in a sauce pan until it boils.
  • Step 4: Stir in the sugar Add sugar ¼ cup at a time; stir it until it is completely dissolved and the solution is clear. This may take a while, so be patient!
  • TIP: If you have a candy thermometer, place it in the sugar solution; it should be ready at 240 degrees Fahrenheit.
  • Step 5: Remove from heat and pour Remove your pan from the heat and carefully pour the sugar solution into the glass jar. Fill it close to the top and let it cool.
  • TIP: If you want to add candy flavoring or food coloring, stir in a couple drops after removing the solution from the stove; then pour it into the jar.
  • Step 6: Store the jar and watch crystals grow Put your jar in a cool, quiet area. It will take a week to ten days for crystals to form on your string.
  • Step 7: Remove rock candy from jar Remove your string from the jar when it is covered with sugar crystals. Now you can taste the chemical principles of precipitation and evaporation for yourself.
  • FACT: In 2008, scientists discovered the first sugar molecule in space, 26,000 light years away, supporting the idea that life could develop on other planets.

You Will Need

  • A clean piece of cotton string or twine
  • A clean glass jar
  • A paper clip or galvanized washer
  • A pencil
  • Popsicle stick
  • or skewer
  • 1 c. water (optional) (optional)
  • 2 c. granulated sugar
  • Patience
  • A candy thermometer (optional) (optional)
  • Candy flavoring (optional) (optional)
  • Food coloring (optional) (optional)

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