How to Make Rock Candy or Sugar Crystals 22


Rock Candy or Sugar Crystals

Sugar crystals are one of the few types of crystals you can grow that you can eat. (Anne Helmenstine)

Sugar crystals are called rock candy because these hard crystals are edible. Sugar (sucrose) crystals are one of the few types of crystals you can grow and eat. You can eat the natural clear crystals or you can color and flavor them.

Rock Candy Materials

You only need a few common kitchen materials for this crystal project:

  • 3 cups sugar (sucrose)
  • 1 cup boiling water
  • food coloring (optional)
  • flavoring (optional — good choices include cherry, peppermint, and cinnamon)
  • clean glass or plastic jar
  • wooden skewer or cotton string

Grow Sugar Crystals

The procedure is really easy.

  1. Dissolve the sugar in the boiling water. You can heat the sugar solution on the stove or in the microwave if you have trouble getting the sugar to dissolve.
  2. Add a few drops of food coloring and flavor, if desired.
  3. Allow the solution to cool a bit before pouring it into your jar. You don’t want to get burned!
  4. Pour the sugar solution into a jar. Place a wooden skewer into the jar or else hang a string into the middle of the jar, tied to a pencil or butter knife.
  5. Place the container somewhere it won’t be disturbed. You may wish to cover the jar with a paper towel or coffee filter to allow evaporation while keeping the crystal solution clean.
  6. It may take a few days to get good crystal growth. If you see crystals forming on the top of the jar, you can remove them and eat them. If you leave them, these crystals will compete with your stick or string for sugar and will reduce the size of your crystals.
  7. Remove the crystals and enjoy them! If you want to store the crystals before eating them, keep them in an airtight container so humidity in the air won’t make the rock candy sticky.

If you enjoyed growing sugar crystals, how about trying another easy crystal-growing project?


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22 thoughts on “How to Make Rock Candy or Sugar Crystals

    • Anne Helmenstine Post author

      You can add it afterward, but the solution thickens quickly, so it’s a bit easier to mix in flavor and color when it’s hot. It’s up to you. If you want to use one solution to make multiple colors and flavors, by all means, add it later 🙂

    • Anne Helmenstine Post author

      You can. It’s easy to grow the crystals on a pipecleaner, but I’m not sure the plastic and metal in them would be good for making an edible treat.

    • Anne Helmenstine Post author

      Samantha, how long it takes depends on humidity and temperature. So, the time required varies according to conditions.

  • Jen

    Does one recipe make just one stick of rock candy or can you divide the recipe into several glass jars with sticks? Just wondering if I would need to double the recipe or if it will make smaller sticks of rock candy divided?

    • Anne Helmenstine Post author

      It depends on how big you want the sticks of rock candy to be. You can divide the recipe into jars with separate sticks or you can double/triple the recipe to use multiple larger jars. Or, you can even use one large container with multiple sticks, if you can figure out a way to keep them from touching each other and the side/bottom of the container. Hope this helps 🙂

  • Kimba Lee

    Will a “convection oven” help speed the process? I was thinking of putting the jar in the convection oven at the lowest temperature .. the circulating air would speed evaporation (?)

    • Anne Helmenstine Post author

      Increasing the temperature increases the solubility of sugar, so in that respect a convection oven (or even higher room temperature) slows the rate of crystal growth. On the other hand, the circulating air increases the rate of evaporation, so eventually the solution saturation will increase. You could try placing the solution in a convection oven for a while and then removing it to room temperature. But, I wouldn’t keep the solution in the oven forever.

  • Camila

    I divided into 3 smaller jars, then added food coloring. But i think it was a mistake to use edible “extracts” they are part oil and part alcohol. Because it’s been 2 days, going on 3 and i have NOTHING 🙁
    Maybe a couple of tiny crystals in the surface.

    • Anne Helmenstine Post author

      Hi Camila,
      Extracts work, but they might reduce the saturation of the solution. You can stimulate crystal growth by refrigerating the solution or by increasing evaporation of water.

  • Camila

    I refrigerated one and left 2 room temp (it’s been hot lately) but i only got a few crystals near the surface around the stick and near surface un the walls.
    I don’t want to throw it out bc i wasted 3 cups of sugar x_x

    • Anne Helmenstine Post author

      Another thing you can try is putting it in the freezer. All that sugar should keep the liquid from freezing but may knock the crystals out of solution.