Rock candy or sugar candy also called rock sugar, is a type of confection composed of relatively large sugar crystals. This candy is formed by allowing a supersaturated solution of sugar and water to crystallize onto a surface suitable for crystal ... Read More nucleation, such as a string, stick, or plain granulated sugar. Heating the water before adding the sugar allows more sugar to dissolve thus producing larger crystals. Crystals form after 6–7 days. Food coloring may be added to the mixture to produce colored candy.