How to Grow Rock Candy
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As a kid, I had several crystal growing kits that I just loved. I’ve always been fascinated by rocks and crystals and how they form. It’s easy for me to get excited about any similar project even as an adult. We’ve already made Borax crystals, and those are certainly beautiful, but what about crystals you can eat? My kids had been asking me about rock candy for a long time, and we finally decided to try our hand at making some. We decided to get a little fancy with our candy sticks and flavorings, but all you really need to have for this is sugar, water, and some kind of stick or string for the sugar crystals to grow on. Just like the Borax crystals, it’s all about creating a supersaturated solution. This one just happens to be edible.
Supplies:
Wooden sticks/skewers
Sugar
Water
Glass jars/containers
Plastic wrap/paper towels
Optional:
Food coloring
About the supplies…
I nearly drove myself crazy trying to decide which jars to use and what size. Few posts I read gave specifics about theirs, and I wanted to use jars that held enough but not too much. I actually have quite the collection of jars because we wash them and use them for projects or storage all the time. I knew I wanted to use six of them, though, and I couldn’t find six matching jars. So I ordered some 16oz jars from Target. They are so pretty that I will definitely find a use for them when we’re done making rock candy. I wanted matching jars for easy math, but really I could have used whatever I had. I could even have used drinking glasses or stemware!
I found actual rock candy sticks, but you could also use any kind of wooden skewer. Some people even just suspend string in the jar. I like the idea of sticks because it just seems like it would be easier to eat the candy that way.
I already had some gel food colorings on hand, so that’s what we used to color our candy, and I found a set of flavorings that the kids got really excited about. I just saw this flavor set, though, and I have a coconut-loving kid who might have been even more excited.
The process…
The first thing we needed to do is form a base layer for the crystals to form on. To do this, we took our sticks and wet the bottom 2/3 or so. Then we rolled them around in some sugar on a little plate. I used a spoon to better cover them, and then just left them to dry. It’s important that they dry completely so that the sugar doesn’t just wash off when you suspend the sticks in the solution. I only intended to let them dry while I prepared the sugar solution, but when I realized I wasn’t going to be able to do that until the next day, I put a paper towel over them and left them overnight.
I read conflicting accounts of how much sugar to use—anywhere from a 2:1 to 4:1 sugar to water ratio. I decided to aim for 3 and see how it went. Since I was filling 6 jars, I used 4 cups of water, which meant I needed at least 12 cups of sugar. A 4 lb bag of sugar holds about 9 cups of sugar, so I made sure to have two bags on hand.
I boiled my 4 cups of water in a large pot to allow plenty of room for the sugar.
I kept the water boiling as I started adding the sugar a cup at a time, stirring to make sure it all dissolved. The kids helped a little with the stirring, but they generally do not enjoy the heat. I really don’t blame them.
I added 12 full cups plus a little extra. It was getting a little harder to tell if the sugar was still dissolving completely, but I decided to stop there. I turned off the heat and let the solution sit for almost 30 minutes to cool down.
Next I lined up the jars and carefully started pouring the solution into them. I started out using a little funnel, but I thought it was easier without. I poured a little at a time into each jar and kept going back and forth until the solution was gone and the jars had close to an equal amount. I would have preferred to fill up the jars even more, but this worked just fine.
This is where the kids really got involved. Since there are three of them, they each claimed two sugar sticks (I guess I’ll have to make my own), and since we were doing a rainbow, they chose their colors and appropriate flavors. We only used about two drops of color per jar, and that was enough to get some intense colors. We did add a few more drops to the orange jar, because it looked very very close to the yellow, but there is definitely a difference in the final product. The purple seems extra dark, and that may be because the grape flavoring is also purple. The flavorings box says that a little goes a long way, so although we didn’t know how much to add, we just poured a very little bit and hoped for the best. I was actually afraid we added too much, but as it turns out we probably could have added even more.
I took over again when it was time to suspend the sticks in the jars. The openings of our jars are the perfect size for a clothespin to lay across. I stuck the stick in the middle of the clothespin and arranged it so that it hung about an inch above the bottom of the jar. Then I pushed them up against the wall and draped a some plastic wrap across them (you could use paper towels if you’d prefer). I actually knocked some of the clothespins crooked in the process, but I was able to straighten them and still get everything covered. The kids thought it was hilarious, and it showed them why we needed to be extra careful not to mess with the jars.
Then it was time to wait.
And wait.
Still more waiting.
I actually didn’t mind this part. Since I didn’t get to eat this batch of candy (ahem), my favorite part was watching the crystals develop every day. It was really, really cool to see. We started ours on a Tuesday and took them out the following Wednesday, so they had over a week to grow. We got some pretty large crystals there at the end!
When I pulled the candies out of the jar, I first had to use a knife to break up the layer of crystals that had formed across the top of the solution. It wasn’t very thick, and this was very easy to do. I had to give the sticks a good tug to break them loose from the bottom of the jar. In the future I might give myself even more room at the bottom of the jar and/or pull the candy out sooner, but the kids didn’t see anything wrong with them the way they turned out, so I’m happy with them.
Once I actually got them out of the jar, I let the excess syrup drip into the jar, and then put them on paper towels while I pulled out the rest. It only took a few minutes for them to dry, and then I was able to annoy the kids by taking lots of pictures before I’d let anyone else touch or eat the candy.
Just look at these beauties! The verdict on taste? According to the kids, not bad! We have a lot of all of our supplies, so we’ll keep experimenting with the flavorings. But I definitely count this first batch as a success.
To clean up, I rinsed out everything I could, and then poured a little water in the jar and put it in the microwave. After 40 seconds (the jar was hot!) I was able to break up the crystals at the bottom of the jar with a spoon. I rinsed those out, and the jar was ready to be washed.
Now I’m wishing I’d made a hot water bath to put the jars in before I pulled the candy sticks out. It might have helped loosen them without breaking the tips. Something else to try next time!
