What is Rock Candy?

Mary McMahon
Mary McMahon

Rock candy is a candy made from large chunks of sugar which are grown on a string or stick. Because it is made from pure sugar, this candy will be naturally clear and extremely sweet. It may be eaten plain, dissolved in sweet drinks, or used as a garnish on desserts. Since the process for making rock candy is very straightforward, many people like to make it at home, and some teachers use it to illustrate crystal formation to young students.

Rock candy is made from pure sugar.
Rock candy is made from pure sugar.

To make rock candy, water and sugar are combined to make a supersaturated sugar solution. The solution is so high in sugar that no more sugar can be dissolved in it, causing added sugar to sink to the bottom. A substrate for crystal growth such as a stick or string is lowered into the solution and left undisturbed for a few days to a week, allowing crystals to form on the substrate as the water evaporates. When the substrate is removed, it is covered in very large, jagged sugar crystals.

Excessive consumption of sugary substances, such as rock cnady, may cause tooth decay.
Excessive consumption of sugary substances, such as rock cnady, may cause tooth decay.

Many people add food coloring to their rock candy to make it more visually interesting. Flavoring may be added as well, for people who want to taste something other than pure sugar. Sticks of this type of candy are often available in candy stores and along the seashore and similar vacation spots. The crystallized sugar is also sold in bulk for restaurant use as a decorative garnish.

To make rock candy, boil one cup of water and add two cups of sugar, stirring constantly and allowing the mixture to boil again. These amounts can easily be increased or decreased if desired, as long as you keep the ratio the same. Once the sugar has completely dissolved, pour the water into a jar and dip a string or stick into it. If you wish to add color or flavorings, do so after the sugar has dissolved, but before you pour it into a jar. Once the string is saturated, pull it out and allow it to dry. This will create seed crystals, which will allow the sugar crystals to be larger and more even.

Once the stick or string has dried, dip it back into the jar of dissolved sugar and allow it to sit until large crystals form. Try to avoid moving or jostling the jar, as this can disrupt the formation of the crystals. Once big, even crystals have formed, the rock candy can be removed from the jar and served or wrapped in wax paper for later consumption.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


It is what I'm doing for my science project, but I am seeing how the presence of seed crystals affects how fast it grows.


Could anybody tell me how much sugar syrup I need to make 30 pieces of rock candy?


What is a natural dye alternative for making blue rock candy? My daughter has to make rock candy swizzle sticks for her science class, but I hate to let her eat anything with synthetic dyes in it, and I know the chances of her not eating it after we make it are nil.

What would some good alternatives be?


If I were going to make rock candy crystals as part of an experiment for my fourth graders, how would you present the rock candy/science connection?

I mean, I can obviously connect it to the formation of crystals, but do you think that I should include any of the chemistry that goes on in the rock candy making?

Also, what are some good rock candy experiments that you can do with the candy after you make it?

I have never taught a science module before, so I would appreciate any and all input.



I absolutely love rock candy. When I was young, I used had read about Laura Ingalls Wilder eating rock candy strings and thinking it was so great.

So my mom (in one of her highlights, I feel) actually taught us how to make rock candy sticks. She even taught us about the rock candy chemistry connections, which was pretty cool.

I still to this day do this with my kids too -- it's a great little project, and the results of the experiment are literally sweet!


Would this a be a good science project for me to do this year?

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