Step 1

Heat 2 cups (473 ml) water in a microwave or a pot, bringing it to a boil. Get an adult to help you if you're not allowed to use the stove--boiling water can be extremely dangerous if you spill it on yourself.If you don't have access to a stove, you can use a microwave instead. Combine the sugar and water in a microwave-safe glass and heat it for two minutes on high. Stir the sugar water and microwave for another 2 minutes. Stir the mixture a third time and the sugar should dissolve almost entirely into the water.Use purified water if possible. The sugar can attach to impurities in the tap water and create a crust that will prevent water from evaporating and prevent the crystals from growing on your string instead.Make sure you handle the pot or microwave-safe glass with hot pads or oven mitts so you don't burn yourself.

Step 2

Stir in the 4 cups (946 g) of sugar in 1/2 cup (118 g) increments. Stir with a spoon after each addition until the sugar is dissolved into the water. As the water becomes more saturated with sugar, it will take longer for it to dissolve in the water. It may take as long as two minutes for the sugar to dissolve.Stir the solution until the water is clear. If the solution is cloudy or you find the sugar stops dissolving, turn the heat up so the water reaches a vigorous boil. Hot water has a higher saturation point than cool water, so turning up the heat should allow you to mix in the rest of the sugar.

Step 3

Remove the solution from the heat and allow it to cool for 15-20 minutes. You don't want any undissolved sugar to remain on the bottom of the pot. If undissolved sugar ends up in the jar or glass where you grow the rock candy, crystals will attach to the undissolved sugar and not to your string or stick.If you have undissolved sugar that didn't mix with the boiling water, you may want to pour the solution through a strainer and only retain the liquid.The solution you have made is a super-saturated solution, meaning the water has absorbed more sugar than it would have absorbed at room temperature. As the solution cools, the water saturation point of the water will become lower, and it will no longer be able to hold the amount of sugar. The dissolved sugar will be unable to stay in liquid form, and will instead crystallize on the string or stick you provide.

Step 4

Add food coloring and/or flavoring if you don't want plain rock candy. Try to coordinate the color to the flavor--blue with blueberry, red with strawberry, purple with grape--so the flavor is clear. Make sure you stir the solution thoroughly so the flavor and color is evenly distributed.You only need a few drops of flavoring, but try to make the solution dark with color for the best results.Try mixing in drink mix, like Kool-Aid, for color and flavor.Try adding a splash of fruit juice for lemon, lime, orange, or other fruity flavored candy.Try different extracts like peppermint, strawberry, vanilla, or even banana.

Step 5

Pour the solution into a large glass or jar where you plan to grow your rock candy crystals. The glass or jar should be tall and cylindrical and made of glass--plastic may melt when you pour in the hot solution. Fill the glass almost to the top.Make sure the glass is clean and contains no dust particles. Even dust can give the sugar crystals something to cling to, and you only want them to settle and grow on your string or stick.Cover the glass with a piece of wax or parchment paper to prevent dust from settling on the top of the solution.This recipe, since it uses only one large jar of glass, yields one candy. If you want to make multiple small candies or do not have a large jar, you can divide the solution into smaller jars. The yield would then be as many as your jars.