Making rock candy – 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.

Things You'll Need

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

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

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

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

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.

Heat 1 cup water to boil.

Dissolve 2 cups sugar in boiling water.

Add a few drops food coloring if you like.

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


  • 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.