This homemade candy recipe is a great at home or in the classroom science experiment that kids will love because they can eat it too!
If you really want to capitalize on the learning opportunity here, follow the precooking steps. Otherwise, skip right to the candy recipe below.
- Write down predictions about what will happen to the sugar during the homemade candy recipe.
- Have a piece of paper with a line down the middle.
- On one side, the child should use a pencil to draw the sugar crystals as they appear through a magnifying glass.
- Leave the other side of the paper blank, the child can draw the rock candy once it is finished.
- Have the child write about how the two pictures look the same or different and why.
The Homemade Rock Candy Recipe
- 4 cups sugar
- 2 cups water
- Food Coloring
- Small saucepan
- Wooden spoon
- Candy thermometer
- Large clean glass jar
- Measuring cup
- Cotton string, screw & pencil – or – Wooden skewer & bulldog clip.
- If you are using cotton string, you will need a weight to hang on the string – such as a screw or a galvanized washer, plus a pencil or wooden dowel, to suspend the string in the jar.
Tie the weight to one end of the string, and then tie the other end to the middle of the pencil. The string should be about two-thirds as long as the jar is deep.
- If you are using a wooden skewer, you will need a large bulldog clip or two pegs. This is my preferred method, trim the skewer until it is just slightly taller than your jar. Attach the skewer to a couple of clothes pins and balance them across the top of the jar.
Or use a bull dog clip to hold the skewer in place (you will need a clip long enough to balance across the top of the jar).
- Wet the skewer or dampen the string and then roll it about in the sugar, then set aside to dry. This will give the sugar crystals something to catch hold of once the crystals begin to form.
- Heat the water in the saucepan over medium-high heat until it comes to a boil. Whilst boiling, add the sugar one cup at a time stirring each cupful until dissolved before adding the next one. Continue to stir the solution until it grows clear and it reaches a rolling boil.
- Remove the solution from the heat and add any flavoring or coloring that you may be using now.
- Allow to cool slightly then carefully pour it into the jar, you may find it easier to transfer the syrup into a jug first or to pour it through a funnel.
- Place the prepared skewer or string into the syrup making sure it doesn’t come into contact with the sides or bottom of the jar.
- Cover lightly with plastic wrap or paper towel and leave to sit in a cool place, where it can sit undisturbed, for several days. Be patient as this will take at least a week.
- You can check each day to see how much your crystals have grown. If you see a large amount of crystals forming on the bottom of the jar pour the solution into a clean jar. This will encourage the crystals to gravitate towards the skewer rather than the bottom of the jar.
- At the end of the week, the crystals on your string should be clearly defined, with sharp right angles and smooth faces of various sizes. If for any reason the experiment doesn’t work pour the syrup back into the pan and dissolve another cup of sugar into it.
Homemade candy recipe information for discussion and teaching
Why do the sugar crystals form into rock candy in this way? Two systems are at work here to cause the sugar crystals to form.
- First, you have created a supersaturated solution by first heating a saturated sugar solution (a solution in which no more sugar can dissolve at a particular temperature) and then allowing it to cool. A supersaturated solution is unstable – it contains more solute (in this case, sugar) than can stay in a liquid form – so the sugar will come out of solution, forming what’s called a precipitate. This method is called precipitation.
- The other is evaporation – as time passes, the water will evaporate slowly from the solution. As the water evaporates, the solution becomes more saturated and sugar molecules will continue to come out of the solution and collect on the seed crystals on the string. The rock candy crystals grow molecule by molecule. Your finished homemade rock candy will be made up of about a quadrillion (1,000,000,000,000,000) molecules attached to the string.
In most states, students are expected to have an understanding of these words and concepts by fourth grade.
Supersaturated, Solute. Evaporate, Evaporation, Precipitate, Precipitation.