2 cups water
4 cups sugar
Optional: 1/2 to 1 teaspoon flavoring extract or oil
Optional: 2-3 drops food coloring
4 Mason Jars
Clean the glass jars thoroughly with hot water. For each jar, cut a length of a thick cotton thread a few inches longer than the height of the jar, and tape it to a pencil. Wet each thread with water, and roll it in sugar. This base layer gives the sugar crystals something to grab when they start forming. Set these aside to dry while you prepare the sugar syrup.
Place water in a medium pan and bring to a boil. Begin adding the sugar, one cup at a time, stirring after each addition. Continue to stir and boil the syrup until all of the sugar has been added and is completely dissolved. Remove the pan from the heat. If you are using colors or flavorings, add them at this point. When using an extract, add 1 teaspoon of extract; for flavoring oils, only add 1/2 teaspoon. Add 2 to 3 drops of food coloring and stir to ensure an even, smooth color.
Allow the sugar syrup to cool for approximately 10 minutes, then pour it into the prepared jars. Lower one sugared string into each jar until it hangs about 1 inch from the bottom. Carefully place your jar in a cool, dark place, where it can sit undisturbed. Cover the top loosely with plastic wrap or a paper towel. You should start to see sugar crystals forming within 2 to 4 hours. If you see no change after 24 hours, try boiling the sugar syrup again and dissolve another cup of sugar into it. Then pour it back into the jar and insert the string or skewer again.
Allow the rock candy to grow until it is the size you want. Don’t let it grow too large, otherwise it might start growing into the sides of your jar. Once it has reached the desired size, remove it and allow it to dry for a few minutes, then enjoy or wrap in plastic wrap to save for later.