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. [2] X Research source Make sure you handle the pot or microwave-safe glass with hot pads or oven mitts so you don’t burn yourself.
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. [4] X Research source 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. [5] X Trustworthy Source Science Buddies Expert-sourced database of science projects, explanations, and educational material Go to source
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. [7] X Research source
You only need a few drops of flavoring, but try to make the solution dark with color for the best results. [9] X Research source 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.
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. [10] X Research source Cover the glass with a piece of wax or parchment paper to prevent dust from settling on the top of the solution. [11] X Research source 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.
Use a string made from natural fiber, like twine or cotton. Fishing twine or nylon string are too smooth and it will be difficult for the sugar crystals to find crevices to cling to and grow. [13] X Research source You can also use a washer or screw to weight the string, or even another piece of rock candy, which may help your crystals grow faster. [14] X Research source The pencil should be long enough that it can rest on the top of the glass without falling in. You can also use a butter knife, skewer, or popsicle stick instead. A butter knife or popsicle stick may be more stable, as they can lay flat on top of the glass and won’t roll.
You must make sure the string is completely dry before you proceed to the next step and be very careful not to knock off any of the seed crystals when you place the string in the solution. [16] X Research source You can skip this step or try to speed it along by wetting the string and rolling it in granulated sugar (just make sure the string is completely dry before you put it in the glass and the sugar isn’t falling off), but making seed crystals will make your rock candy grow faster and increase your chances of success in growing crystals. [17] X Research source
As the water evaporates, the remaining solution becomes more saturated with sugar, and the water must force the sugar out. The sugar molecules will collect on the string, forming your rock candy crystals. [19] X Research source Tape the pencil to the jar to keep it from rolling or moving while your crystals form. [20] X Trustworthy Source Science Buddies Expert-sourced database of science projects, explanations, and educational material Go to source
If you want to grow crystals quickly, but don’t care if they get big, put the glass in a sunny spot so that the water evaporates quickly. [22] X Research source Vibrations can negatively affect your crystal growth. Keep your glass off the ground (and away form the vibrations of people walking on the floor) and away from sources of music or noise, like a stereo or television. [23] X Research source
If the rock candy is stuck to the glass, run some hot water on the bottom of the glass. This should loosen the sugar enough so that you can pull your candy out without damaging it. [25] X Research source
Allow the skewers to dry completely before proceeding to the next step. If the sugar isn’t firmly stuck to the wood, it may fall off in the glass and the crystallization will occur on the sugar on the bottom of the glass and not on your skewer. [27] X Research source
Try to keep the tip of the skewer about 1 inch (2. 5 cm) from the bottom of the glass. [29] X Research source
Your skewer should be held securely by the clothespin and still be in the very center of the glass. Cover the glass with a paper towel. You can tear a little hole for the skewer to poke through the towel.
If there is a crust on top of the surface of the water, use a butter knife to gently break through the crystals, avoiding the crystals near your skewer. [33] X Research source If the rock candy is stuck to the glass, run some hot water on the bottom of the glass. This should loosen the sugar enough so that you can pull your candy out safely without damaging it. [34] X Research source
