Rock candy

Large, clear sugar crystals grown slowly from a very concentrated syrup onto a string or stick.

Rock candy: Clear and colored rock candy crystal sticks standing in a glass
  • Chocolate, sugar and confectionery
  • Iran

Also called: candy sugar

Rock candy is made by dissolving as much sugar as possible in boiling water, letting the syrup cool slightly and hanging a string or wooden stick in it. Over about a week, sugar crystals form and grow on the surface. A stick lightly rolled in sugar first gives the crystals a place to start.

It can be colored and flavored, and it is used to sweeten tea and coffee in many countries. Growing rock candy is a popular kitchen science project, since it shows crystallization in a visible way.

Make it at VanillaGoods

Related entries

Sources

Written by VanillaGoods in our own words from these sources. Last reviewed October 15, 2026.

  1. Science of Candy: Rock Candy: What's Going On?, Exploratorium (science museum, San Francisco)
  2. Sweet Science: How Sugar Molecules Are Manipulated in Candy Making, Yale National Initiative / Yale-New Haven Teachers Institute