How do I make large rock candy?

Updated April 08, 2017

Rock candy is one of the most popular in school and at home science experiments out there. Rock candy is formed when dissolved sugar crystallises into a solid crystal again but on a much larger scale. The event is simply the restructuring of sugar crystals to form one solid larger version. Rock candy is one of the oldest forms of candy as it is composed simply of sugar and water with optional flavouring and colouring. To make large rock candies, large jars, durable candy sticks and an extended crystallisation period are required.

Mix together 4 cups of sugar with 2 cups of water (or any 2:1 ratio of sugar to water depending on the amount of rock candy you wish to create) in a medium size saucepan. Bring the mixture to a boil over medium heat while stirring constantly until all of the sugar is dissolved. Remove from heat.

Add any colouring or flavouring to the mixture. If adding colouring, drop one to two droplets of liquid food dye to the mixture (adding more when needed) and stir. Add flavour extracts such as vanilla, mint, lemon, raspberry and any other bottled flavour 1 tsp at a time until the desired flavour concentration is reached.

Pour the liquid sugar mixture into pint-sized canning jars 3/4 of the way full. Dip each candy stick (available at craft and confectionery stores) into the jar. Remove and lay flat on a piece of waxed paper to dry. Cover each jar with plastic cling wrap or waxed paper. If using waxed paper you must tape or rubber band it so that it sits on the jar securely. The top of the jar must be covered to prevent dust, dirt and insects from entering the jar and contaminating the rock candy.

Insert one prepared stick into the top of the jar. The stick should not reach the bottom to allow for a rounded candy crystal tip. To keep the stick suspended, look for candy sticks with end beads or nobs so that it catches on the lid like a grappling hook. If such sticks are unavailable, clamp a large clothespin (the clothespin must exceed the diameter of the jar) on the stick to suspend it inside of the jar.

Place the jar in a clean, cool undisturbed area and allow to grow (without touching) for a maximum of two weeks for large rock candy wands. The longer you let the crystals grow, the larger the rock candy will become. Two weeks is the maximum growth period, any longer and your candy will be at risk for contamination, possible bacteria and loss of flavour.

Things You'll Need

  • 4 cups sugar
  • 2 cups water
  • Glass pint canning jars
  • Candy sticks or dowels
  • Food colouring and flavouring
  • Plastic cling wrap or waxed paper
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About the Author

Mallory Ferland has been writing professionally since her start in 2009 as an editorial assistant for Idaho-based Premier Publishing. Her writing and photography have appeared in "Idaho Cuisine" magazine, "Spokane Sizzle" and various online publications. She graduated from Gonzaga University in 2009 with Bachelor of Arts degrees in history and French language and now writes, photographs and teaches English in Sao Paulo, Brazil.