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Fun With Kids: Make Your Own Rock Candy

May 5, 2010 | by Ed

Here’s a fun and educational way to help your kids learn a bit of chemistry. When I was a child, I remember making rock candy with my mother and childhood friends in the neighborhood. It was an easy (and affordable) way to make my own special treat, and stay out of the kitchen after the holidays!

rock candy

What you'll need:

1 one-quart glass jar with a wide mouth
1 clean string
1 clean paper clip
1 pencil


Fill the jar with sugar. Then add boiling water slowly, stirring with a long handled spoon until the sugar is entirely dissolved.

Tie the paper clip to the string. Measure out the string to be as long as the jar is tall, plus two inches. Tie the other end of the string to the pencil, and lower the end with the paper clip into the jar until it is just above the bottom.

Take the string out and put it on a piece of wax paper until it dries. (Usually about an hour or two.)

Now put the string back in the jar and let it stay there for several days.

Rock candy crystals will form on the string, and the longer the string is in the jar, the bigger the crystals will be.

The science behind the sweet treat:

There are two processes at work. The first is precipitation. The liquid in the jar has more dissolved sugar than it can hold, and the sugar crystals will precipitate out of the liquid and onto the string where the dried sugar crystals are. As they do, they form large crystal.

The other process is evaporation. Water is evaporating from the jar, and the sugar is growing more concentrated, making the crystals grow.

For fun, you can ad a few drops of food coloring to the sugar solution.


Topics: Recipes