Facts About Rock Candy Crystals

Written by nessa speirs | 13/05/2017
Facts About Rock Candy Crystals
Rock candy is made from crystallised table sugar, or sucrose. (Antique Cup image by Vanessa van Rensburg from Fotolia.com)

Rock candy is an appealing commodity not only because of its aesthetic beauty, but because of its easy production. The crystallisation of sugar molecules causes this candy to form.


The rock candy crystal is produced using sucrose, or table sugar. Sucrose is used to produce rock candy because fructose and glucose can prevent large crystals from forming. The colour of the crystals can easily be altered by adding food colouring, which does not affect their growth. Because it requires pure cane sugar, rock candy crystals cannot be produced in sugar-free alternatives.

Crystallisation Process

The rock candy crystals are formed through a process called "supersaturation"-- dissolving sugar in heated water until it has reached its saturation point. Then a string or wooden stick is placed in the water and left to cool. As it cools, the sucrose forms on the item in large crystals.

Heating the water increases its capacity for dissolving sugar. At higher temperatures, water evaporates away but the sucrose is able to remain in solution, leaving a higher ratio of sugar to water and making the production of crystals more successful.

The Rock Candy Industry

In the 1800s, rock candy was sold most often in saloons to ease patrons' cold symptoms. It could easily be made by dissolving the sugar into rye whiskey. The industry so depended on sales in saloons that it failed when the Prohibition Act took effect in the early 1900s.

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