How to Make Sugar Crystals in a Jar

Make your own sugar-crystal candy.

Growing large sugar crystals in a jar is a science project that creates a sweet candy. Sugar is already made up of many small crystal structures. When dissolved in water and left alone, these crystals bond to each other to form even larger crystal structures. A supersaturated sugar mixture is added to a jar then left to slowly evaporate. This mirrors the process by which other mineral crystals are formed in nature. The more slowly the water evaporates, the large the crystals grow.

Things You'll Need

• Hot water
• Bowl
• Sugar
• Measuring cups
• Food coloring
• Jar
• Cheesecloth
• Rubber band

Instructions

1. Pour 2 cups of hot tap water into a bowl. Slowly stir in 1 cup sugar until it is completely dissolved.

2. Add one or two drops of liquid food coloring to the sugar mixture, if desired. Pour the mixture into a clean glass jar.

3. Place a square of cheesecloth over the top of the jar and secure with a rubber band. This prevents dust from settling on the forming crystals.

4. Set the jar in an area where it won't be disturbed. Leave it alone for at least a week, or until all the water has evaporated out of the jar.

5. Remove the cheesecloth once the crystals are fully formed along the sides and bottom of the jar. Break them off and eat them if desired.

Tips & Warnings

• Tie a cotton string to a pencil and lay the pencil over the jar so the string dangles in the sugar water. The crystals grow along the string, making rock candy.

• Grow non-edible crystals by substituting Epsom salt or alum for the sugar.

• The crystals only grow correctly if as much sugar as possible is dissolved in the water, a process known as supersaturating. Do not try to use less sugar or the experiment will not work.

References

• Bellevue College: Growing Crystals for Fun

Resources

• Read this Article in Spanish