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Experiments with Sugar Crystals

Sugar has a crystalline structure, which makes it a suitable and readily available medium for crystal experiments. When a large amount of sugar is dissolved in water, it forms even larger crystals as the water evaporates away. Unlike some other items used for crystal making, sugar is safe to handle and so works well for experiments involving children.

Rock Candy
- Rock candy is an edible sugar crystal experiment, making it popular with kids and adults alike. Dissolve 2 tbsp. of sugar into 4 tsp. of hot water then pour the mixture into a glass jar. Insert a small stick or a string into the sugar water so the crystals have something to grow on. To help the crystals adhere to the stick or string, roll it first in sugar to create a thin coating of seed crystals. As the water evaporates, the dissolved sugar crystal molecules reform on the string or stick, making large, block-shaped crystals. Once the water is completely evaporated, you can study the crystal formations then enjoy eating the candy.
Controlling Crystal Growth
- The more slowly a sugar solution cools down and evaporates, the larger the crystals grow. Try slowing down the cooling and evaporating process by placing a jar of sugar solution in an insulated bag or ice chest. Make a second batch of sugar solution but allow it to evaporate at room temperature. Compare the rate of evaporation between the two jars each day. At the end of the experiment, check to see which jar grew the largest crystals.
Surface Growing
- Crystals naturally grow upon rock surfaces. Experiment to find out which kind of surface is best for crystal growth. Make a sugar solution as you would for rock candy and pour it into two jars. In the bottom of one jar, place a porous stone such as a lava rock. In the second jar, place a smooth river stone. Check the jars each day as the water evaporates. Compare the amount and size of crystals on each stone.

Rocks & Minerals