Rock candy has been around for many years and has been loved by children and adults the world over. Plain rock candy is just a mix of water and a large quantity of dissolved sugar. Rock candy can be made quickly while you enjoy watching these edible crystals grow. Kids can make rock candy themselves--with some adult supervision--to be used as a science project or just to be eaten and enjoyed as a tasty treat.
Boil water. Add 240 ml (1 cup) of water into a medium saucepan. Turn the burner on high and let heat until boiling. Remove from heat. Water can also be heated in the microwave in a microwaveable bowl.
Pour in sugar. Measure out 240 ml (1 cup) of sugar and pour into hot water. Stir until the sugar is dissolved and then add the other 720 ml (3 cups) of sugar. Perform this step quickly because the more the water cools, the less the sugar will dissolve. When the sugar will dissolve no further and starts building up on the bottom of the pan, it means your sugar is saturated. The sugar solution is almost ready to be put in the jar.
Add colouring. Decide which colour you want and get it ready. Add a few drops of food colouring to the pan and stir. If you want a darker colour, add more food colouring. Now is also the time to add flavouring to the sugar solution. This can be any mint or fruit flavouring that you want. You can also decide to not use any food colour or flavouring.
Fill the jar. A mason jar is better than a small relish jar because the bigger the jar, the bigger in size the crystals can grow. Pour the sugar solution into the mason jar. If there is a lot of undissolved sugar in the bottom of the pan, try not to get it into the jar. The crystals will form on the sugar instead of the wooden skewers.
Put in the skewers. Place one or two of the wooden skewers in the jar of sugar solution. You can also use yarn or twine for the crystals to grow on. Don't use a nylon string, as it will be too slick for the crystals to form on. If using yarn or twine, tie several lengths to a pencil or skewer and set over the mouth of the jar so the threads will hang into the mixture.
Wait for crystal formation. Small crystals can start forming after 1 hour. You can then eat them, but if you want larger sugar crystals, give the rock candy a few days to a week to form.