If your kids are like mine, their favourite cooking endeavours probably involve sweet stuff. At our house, cookies came before casseroles, cakes before cauliflower. As they got older, they became quite intrigued with aspects of food science, especially the chemical reactions involved in baking. This tasty experiment requires just a little prep time followed by a lot of patience but kids will have a great time watching the crystals grow and, of course, sampling the finished product. It would be a great project for a school break or for homeschoolers. Kids can do most of this on their own but adults should help with creating the super hot sugar syrup and pouring it into the jars.
2 cups water
4 1/2 – 5 cups granulated sugar
Food colouring (optional but fun)
Clip wooden skewers into the clothes pegs and adjust as needed so that the pegs will rest across the top of the jars and a portion of the skewer will hang down inside. You can have two pegs / skewers per jar. You want the skewers to stay away from the sides of the jar and each other, and there should be about 1 inch of clearance between the skewer and the bottom of the jar.
Keep adding sugar, 1/2 cup at a time, stirring after each addition until it dissolves. After 4 cups, make remaining additions by tablespoonsful rather than half cups. Stop adding sugar when no more will dissolve (my batch took 4 1/2 cups plus a tablespoon). This will take time and patience as it takes longer for the sugar to dissolve each time. Once no more sugar will dissolve, remove the pot from the heat and allow it to cool for at least 20 minutes.
While the mixture is cooling, tilt the pot and dip the bottom portion of the skewers in the syrup then roll them in granulated sugar to put some ‘seeds’ on the sticks. This will help kick-start the sugar crystal growth.
Carefully add two skewers, coated ends down, to each jar, resting the clothes pegs across the mouth of the jars. Be sure they are hanging straight down the middle without touching the sides or each other.
Crystals will also form on the bottom, sides and even the surface of the jars; this is normal. You will be able to easily shatter (and eat!) the solidified sugar layer on the top of the jar to extract the skewers when you are ready.
What’s the science?
The solution you have made is a super-saturated solution, meaning the boiling 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, so the liquid will no longer be able to hold the amount of sugar. The dissolved sugar will be therefore be unable to stay in liquid form, and will instead crystalize on the skewer. If you have a magnifying glass or microscope, take a look at the crystals you’ve grown before you eat them!
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