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Rock Sugar Research: History
Before beginning a science project on rock sugar, it's important to know the history, background and uses of the candy. Rock sugar's first known origins are in the Middle East in the ninth century. Scholars described how they made it by cooling supersaturated sugar solutions. In the West, rock sugar was used as a medicine until the 1700s, when it began being used as a sweet treat. In Shakespeare's play "Henry IV," written in 1596, rock sugar is humorously described as being a great throat lozenge for long-winded talkers. Today rock sugar is commonly used in many countries to sweeten tea.
Preparing the Rock Sugar Supplies
To make rock sugar, you will need a measuring cup, spoon, sauce pan, tall glass jar, a clean string, craft stick, pot holder and a candy thermometer. Tie the string to the middle of the craft stick, dip it in water and roll it in granulated sugar. Place the craft stick across the mouth of the tall glass jar so that the string hangs down into the jar. The string shouldn't touch the bottom. Pour one cup of water into a sauce pan and boil the water on your stove top. Add two cups of sugar to the boiling water and stir it until it dissolves. The sugar water should reach 240 degrees Fahrenheit. Take the pot off the burner. You are now ready to begin making rock sugar.
Making the Rock Sugar
Pour the hot sugar water into the tall glass jar. Let your sugar solution sit for several days until you start seeing large crystals forming on the hanging string. Let the crystals continue to grow for at least three more days. You could leave your solution sitting for 10 days if you want more crystals. The largest crystals grow in thicker sugar solutions and when sitting for a longer period of time. When the rock sugar is finished, pull the string out of the jar and let it dry. You can break it apart and eat it or store it in a covered container.
The Science Behind Rock Sugar Formation
When granulated sugar is heated up into a liquid solution and then begins to cool, it becomes a supersaturated solution. The cooling water can't hold as much sugar as it could when it was hot and so the solution becomes unstable. Because the solution can't hold any more sugar crystals, the crystals attach themselves to the sugary string. That's why it's important to wet the string and roll it in sugar before you start your project: the sugar on the string becomes a starting point for crystal formation. As time passes, water slowly evaporates from the solution, meaning less and less sugar crystals can be held by the solution and more and more stick onto the string.
Rock Sugar Science Project Ideas
One idea testing the science of rock sugar is to try making it with different amounts of sugar: one cup, two cups and three cups. Study which type of solution grows more crystals and the speeds of sugar crystal formation. You can then prove the science behind crystal formation: the more supersaturated a solution is, the more sugar crystals that form. Other science projects variations include growing the largest rock crystal you can, testing what happens when you rapidly cool your sugar solution by putting it in the freezer instead of letting it cool gradually, or testing if you can make salt crystals in the same way that you make sugar crystals.