How to make rock sugar crystals

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How to make rock sugar crystals
Rock is popular particularly at British seaside resorts. (Anmfoto/iStock/Getty Images)

Making rock - which is actually just sugar crystals on a string - can be a remarkably enjoyable and edible science project, as well as a tasty treat. Follow these simple steps to have a batch ready in no time.

Skill level:

Things you need

  • 240 ml (1 cup) water
  • 450 g (2 cups) sugar
  • Food colouring
  • Cotton strings
  • Ice cream sticks
  • A glass
  • Pencils
  • Paper and binder clips

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  1. 1

    Sterilise the glass jar and paper clip by boiling both in water for a few minutes.

  2. 2

    Tie a short piece of kitchen string to the middle of a pencil or ice lolly stick.

  3. 3

    Attach the paper clip to the end of string. (The clip will weigh the string down - this is important later).

  4. 4

    Moisten string lightly and roll in sugar (this helps the crystals form on the string).

  5. 5

    Place the pencil or stick over top of a jar. Make sure clip is in the bottom of jar and the string hangs straight down into jar.

  6. 6

    Heat 1 cup water to boil.

  7. 7

    Dissolve 2 cups sugar in boiling water.

  8. 8

    Add a few drops food colouring if you like.

  9. 9

    Pour sugar syrup into jar and leave for 2 to 3 days or until crystals form on the string.

Tips and warnings

  • Crystals should start to grow in 2 to 4 hours and continue to grow for a couple of days. For big crystals - fast - heat the sugar-water solution a second time and dissolve extra sugar in it.
  • The sugar mixture is very hot and children will need adult supervision.

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