Sweet science: An easy rock candy project for kids
Deanna Clemmer was attracted to science as a child. She loved attending science fairs. “I was always a really big fan of bottle rockets, or the volcanic things with baking soda. As I got older, I just really held onto that childish love for all those things.”
Today, she is a doctoral student in the Upstate laboratory of virologist/immunologist Harry E. Taylor, PhD.
Clemmer shares her love of science with her nephews, with at-home experiments such as making rock candy. (Hear her talk about this and her lifelong love of science in this interview.) This experiment shows how a supersaturated sugar solution creates crystals.
Here’s how:
Ingredients you’ll need
2-3 cups of sugar (1 for each stick) plus a few extra tablespoons
2-3 cups of water
2-3 wooden kebab skewers, each about 6 inches in length
2-3 see-through canning jars, about 12- to 16-ounce size
Clothespins
Food coloring, various colors
Candy flavoring or extracts, optional
How to conduct the experiment
Combine equal parts sugar and water to heat in a saucepan on the stove. This cannot be done in a microwave. Warm the pan until the sugar is dissolved. If you add the sugar to the water slowly, you’ll see it turn cloudy as it dissolves.
Rock candy is easy to make at home.If you’re adding a candy flavor, now is the time to stir it in. Then, remove the saturated sugar solution from the heat and allow it to cool a little.
Next, submerge the skewers in plain water. Spread some sugar on a plate and roll the wet skewers in the sugar. Then set them aside to dry.
Once the skewers are dry, carefully place them in separate jars. Clip each skewer to a clothespin and lay each clothespin perpendicular across the mouth of a jar. Don’t let the skewers touch the jar’s edges or bottom. Let them hang to about an inch from the bottom of the jar.
“Make sure that the sticks are completely dry before you put them in the jar. That is really important,” Clemmer said. “If it’s wet, it’s not going to grow as well. It might not grow at all. Because the rock candy needs the sugar on the sticks to grow, if it’s not dry, it’s going to dissolve in the water.”
When the sugar solution from the stove has cooled, remove the clothespinned skewers from the jars momentarily. Divide the sugar solution among your jars, filling them to an inch or two below the lip of the jar. Stir your food coloring into each jar.
Choose a spot for your jars where you can watch them for the next week, and place them there before returning the clothespinned skewers to the jars.
You may see crystals form within the first 24 hours, but Clemmer encourages patience. “Some kids get a little antsy, and by day three, they’re like, ‘Oh, there’s enough candy on this; I’m just going to eat it.’ But I’ve found that once you leave it for a week, you get that whole skewer that’s in the jar. It’s full of candy crystals. It grows in every direction.”
She and her nephews photograph the rock candy progress each day. “They love to see their experiment working throughout time. And I think that’s very important for kids to be seeing that when you’re patient and you wait for things, amazing things can happen.”
Clemmer said she likes this experiment because it illustrates states of matter in a simple way that’s easy to follow. And, dissolving things in water is something she’s used throughout her scientific career.
“What’s cool about it is, we know that it is sugar water. That’s what we dissolved in the saucepan, right? Now that you’ve put the dry sugar in the sugar water, all of the sugar from the sugar water is going to connect to the skewer. It’s basically simple levels of attraction in just normal stuff that we use to cook and eat.
“Essentially, the dried-up sugar will basically draw all of the other sugar particles that are inside the water, that you dissolved, to the skewer. And that’s why it’s so important that the sugar on the skewer is dry. Because if it’s wet, then it’s just going to dissolve. But if it has something to draw it to, almost like a magnet, a sugar magnet, it’s going to draw all of that sugar to the skewer.”
This article appears in the 2024 Upstate Health magazine, Issue 1.
