Roberta A. Mazzucco
Rock candy is on if the oldest and purest forms of candy. When you make rock candy you can see the shape of sugar crystals on a larger scale. The string provides a place for the sugar crystals to latch onto. As the water evaporates tiny the sugar crystals will encrust the string. Two processes are happening: saturation and evaporation. The string is supersaturated with sugar so it cannot stay in liquid form so it will come out and form crystals. Through evaporation more and more water will be removed from the solution so the crystals will continue to grow until the water is removed. The rock candy grows molecule by molecule.
Materials: 4 cups of sugar, 2 cups of water, a small saucepan, wooden spoon, candy thermometer, small, clean glass jar, measuring cup. Cotton string, a weight to hang on the string (such as a screw or galvanized washer), wax paper, a pencil or dowel (to suspend the string in the jar)
Process:
1.
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Heat the water in the saucepan until it comes to a boil
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2.
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Completely dissolve the sugar in the boiling water, stirring continuously with the wooden spoon until the solution grows clear and reaches a rolling boil.
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3.
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Remove the solution from the heat, and then carefully pour it into the jar. Cover the jar with a piece of wax paper.
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4.
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Tie the weight to one end of the string, and the other end to the pencil. The sting should be about 2/3 as long as the jar is deep. Dip the string into the solution and roll it into some sugar. Allow it to dry.
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5.
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Suspend the string into the solution and let it sit at room temperature undisturbed for several days.
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6.
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At the end of the week the crystals should be growing with sharp right angles and smooth faces of various sizes. The shapes of the crystals will be determined by the way the individual sugar molecules fit together.
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The string is put into the solution and then rolled into sugar in order to give the crystals a place to latch onto. The sugar crystals grow because as the water evaporates over time the sugar will become more saturated and crystals will cling to the string. There are many different recipes for rock candy. This recipe came from the Science of Candy: Rock Candy Recipe (http://www.exploratorium.edu/cooking/candy/recipe-rockcandy.html#).