Making homemade rock candy is a fun science experiment and a delicious treat all in one! Watching sugar crystals slowly grow over several days is fascinating for both kids and adults, making this an excellent STEM activity for classrooms, homeschool lessons, rainy days, or summer break.
Looking for more science experiments for kids? Check out our collection of easy science experiments using household ingredients!
Although rock candy takes about 5–7 days to fully grow, the process is simple, inexpensive, and well worth the wait. All you need are a few pantry staples, glass jars, wooden skewers, and a little patience.
What Is Rock Candy?
Rock candy is made by allowing sugar crystals to slowly grow from a supersaturated sugar solution. As the syrup cools and the water gradually evaporates, sugar molecules attach to the wooden stick or string, forming the large sparkling crystals that make rock candy so unique. Because you can actually watch the crystals form over time, this project doubles as both a homemade candy recipe and a fun science experiment.
We've made homemade rock candy several times over the years and recently updated this post with new photos and a step-by-step video. Every batch turns out a little differently, but that's part of the fun!
We made a huge batch using 8 cups of water and 20 cups of sugar, which filled about 12 small jars. You definitely don't need to make that much! As long as you keep the same water-to-sugar ratio, you can easily make a smaller batch with great results.
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Why You'll Love Making Homemade Rock Candy
- A fun science experiment kids can watch day by day.
- Only a handful of inexpensive pantry ingredients.
- Perfect for STEM lessons, homeschool, and science fairs.
- Customize every jar with different colors and flavors.
- Makes fun party favors and homemade gifts.
What Others Are Saying
We put our skewers through unbleached coffee filters to keep the dust and pet hair out of our jars but allow for evaporation. It seemed to work well.---Julie
I love this activity. I have 3 daughters and we made this one of the nights events during a 12 girl sleep over. I used the smaller mason jars and labeled each jar with the girls names. I did a test 2 weeks before and found that you really need to have a very good sugar base started on each stick to get the best results. We used the solid food coloring and hard candy flavoring. To help with keeping the bugs away I used some of those outdoor pop up nets you use for outdoor dinners over your plates. The girls loved that they got to see a progress report every evening on their Instagrams. Day seven they were all over after school to collect their rock candy. Thank you---Robert
The Science Behind Rock Candy
Rock candy forms because you're creating a supersaturated sugar solution, meaning the hot water contains more dissolved sugar than it can normally hold at room temperature. As the solution cools, the extra sugar has nowhere to stay dissolved, so it begins attaching to the sugar-coated skewer. Over several days, those tiny crystals continue growing until you've created edible rock candy.
Ingredients
- Granulated Sugar: Sugar is the star of this project. As it crystallizes, it forms the beautiful rock candy crystals.
- Water: Hot water dissolves the sugar, creating the supersaturated solution needed for crystal growth.
- Food Coloring: Food coloring gives each batch its fun appearance. Use one color per jar or experiment with different colors.
- Flavoring (Optional): Add a few drops of candy flavoring or extracts after removing the syrup from the heat.
- Wooden Skewers or Rock Candy Sticks: The rough surface gives sugar crystals something to attach to while they grow.
See the recipe card for full information on ingredients and quantities.
How To Make Rock Candy
Step 1: Prepare the Skewers
Trim down your skewers to a reasonable size to fit in whatever jars or cups that you will be using. You'll also want to get rid of the point. Dip them in water, then roll in sugar.
Let the sticks dry completely and set aside. This will give the sugar a base (something to stick to when it starts to crystallize).
Step 2: Make the Sugar Syrup
Heat water on medium-high heat in. a saucepan or large pot (depending on how much syrup you want to make) When it starts to simmer/boil begin adding sugar until you reach a 1:2 to just shy of a 1:3 water-sugar ratio. The mixture will take longer to dissolve the more sugar you add (totally normal). Keep stirring with a wooden spoon until completely dissolved. Remove from heat. CAUTION: it is very HOT!
Step 3: Fill the Jars
Ladle the syrup into your jars using a funnel to catch spills. Add food coloring and, if desired, a few drops of candy flavoring to each jar. Grape, cherry, orange, and lemon are all delicious choices!
Allow the liquid in the mason jars to cool down a bit. Warm or room temperature. Attach a clothespin to each skewer (the ones you dipped in sugar and let dry) and place in the jar.
Step 4: Let the Crystals Grow
Place the jars in a location where they won't be bumped or disturbed. Over the next several days, you'll begin to see tiny sugar crystals form and gradually grow larger. Resist the temptation to move the jars too often—the less they're disturbed, the better your crystals will develop.
Step 5: Remove and Dry the Rock Candy
Carefully lift the rock candy out of the jar and allow the excess syrup to drip back into the jar. Place the rock candy on a parchment-lined baking sheet or wire rack and let it dry for 1–2 hours before serving or wrapping for gifts.
Don't worry about any hardened sugar left behind in the jars—it's easy to remove! Simply fill each jar with very hot water and let it soak for 15–30 minutes. The sugar will dissolve on its own, and any stubborn pieces can be gently loosened with a butter knife or silicone spatula before washing the jar as usual.
How to Store Rock Candy
Once completely dry, wrap each stick in plastic wrap or store it in an airtight container in a cool, dry place. Homemade rock candy will keep for up to one year if protected from moisture.
Tips & Tricks
- Make sure your jars are perfectly clean.
- Use plenty of sugar. A supersaturated syrup is the key to crystal growth.
- Allow the syrup to cool slightly before adding the sugar-coated skewers.
- Don't bump or move the jars while crystals are growing.
- Keep the sticks from touching the sides or bottom of the jar.
- For larger crystals, store the jars away from direct sunlight. Our crystals are small because we grow ours on a windowsill. We like seeing the light shine through the glass and watching the crystals grow.
- For faster growth, place them in a warm location.
- Be patient! Every batch grows a little differently.
What to Expect Each Day
Day 1: The sugar syrup is clear and fully dissolved. Everything looks pretty quiet.
Day 2: Tiny sugar crystals may begin forming on the skewer and around the edges of the jar.
Day 3–4: Crystal clusters become much more noticeable as they continue to grow.
Day 5–7: Most batches are ready to remove and enjoy.
1–2 Weeks: Leave the sticks longer if you'd like larger crystals, provided they aren't attached to the bottom or sides of the jar.
Rock Candy FAQs
The most common cause is not enough sugar in the syrup. The solution must be fully saturated for crystals to form.
This usually means the stick was touching the bottom of the jar or undissolved sugar settled there.
Yes! Stir candy flavoring or extracts into the syrup after removing it from the heat.
The sugar crystals act as "seed crystals," giving new crystals something to grow on.
Absolutely. The crystals will simply be clear.
Cloudiness usually happens when undissolved sugar remains in the syrup or the solution was disturbed while crystals were forming.
Yes. They're simply hardened sugar.
Yes. In fact, many people find wooden skewers produce larger crystals because the rough surface gives the sugar more places to attach.
Freshly removed rock candy is coated in sugar syrup. Let it air dry on a wire rack or parchment-lined baking sheet for 1–2 hours so the excess syrup hardens before serving or wrapping.
Glass jars work best because they can safely hold the hot sugar syrup and allow you to watch the crystals grow. Plastic or foam cups may warp or melt when filled with the hot syrup.
If your family enjoyed making homemade rock candy, be sure to try more of my kid-friendly science experiments and easy homemade treats.
More Kitchen Science For Kids
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Homemade Rock Candy Recipe
Equipment
- funnel
- glass jars
- clothespins
- large pot
Ingredients
- Granulated sugar lots of sugar
- Water
- Food Coloring concentrated for brighter colors
- Wooden Candy Sticks or Bamboo Skewers
- flavoring optional, Lorann is my favorite brand
Instructions
- Trim down your skewers to a reasonable size to fit in whatever jars or cups that you will be using. You'll also want to get rid of the point. Dip them in water, then roll in sugar.
- Let the sticks dry completely and set aside. This will give the sugar a base (something to stick to when it starts to crystallize).
- Heat water on medium-high heat in. a saucepan or large pot (depending on how much syrup you want to make) When it starts to simmer/boil begin adding sugar until you reach a 1:2 to just shy of a 1:3 water-sugar ratio. The mixture will take longer to dissolve the more sugar you add (totally normal). Keep stirring with a wooden spoon until completely dissolved. Remove from heat. CAUTION: it is very HOT!
- Ladle the syrup into your jars using a funnel to catch spills. Add food coloring and flavorings to each jar, if you’d like wouldn't grape, cherry, orange or lemon flavoring be delicious?).
- Allow the liquid in the mason jars to cool down a bit. Warm or room temperature. Attach a clothespin to each skewer (the ones you dipped in sugar and let dry) and place in the jar.
- Place your jars in a safe location and watch the crystals grow!After 5–7 days, or once the sugar crystals have reached your desired size, carefully lift the rock candy out of the jar. Hold it over the jar for 30–60 seconds to allow any excess sugar syrup to drip off.Place the rock candy on a parchment-lined baking sheet or wire rack and let it air dry for 1–2 hours. This allows the sticky syrup on the surface to harden into a crisp sugar coating, making the rock candy easier to handle and enjoy.
Notes
- You can create as much or as little syrup as you'd like as long as you keep the same sugar/water ratio. You are making a nice, sticky, sugary syrup.
- If after 24 hours you don't see any crystal growth, pour each jar of syrup back into the pan (separately) and add more sugar. ¼ c. or so and heat once more until it is a syrup consistency. Roll the sticky skewers in sugar and add them to the jar once more after the syrup has cooled down to be warm (not hot) or room temperature.
- Make sure the skewer isn't touching the bottom or sides of jar/glass. They need room to grow. One skewer per jar works best for regular-sized jars.
Multishopbd.com says
We tried several years ago to make rock candy without success. We’ll give it a try with your recipe.
Suzy Greenwell says
I remember doing this in science class when i was a kid and the ratio was 500 ml of water to 5 lbs of sugar.. This is crazy that i remember this cause im 48 yrs old.. wow how the mind works..LOL
Brandy says
Haha, we remember what is important, right? I never made it as a kid, but had a great time making it as an adult...I just didn't care to eat it. It was fun to watch grow 🙂
Eryn says
After going back and rereading through the process and materials, I wonder if we shouldn't have used the sticks we did. It looks like you guys used wood instead of the candy sticks (like the type you would use for cake pops). I wonder if that makes any difference. Maybe if we don't see any growth after three days we will start over using kabob skewers in hopes it will work better.
Eryn says
Just curious but....my daughter and I are using this as her science project and after one day the glasses looked a little odd. We did three glasses and the surface all have the crystals on top but none on the actual candy sticks. Is that normal? Are we doing this right? We made sure to saturate and roll them in sugar but the sugar base has come off in the water. Please help!
Brandy says
Ours did that too! I don't think we noticed crystals until growing until day 3 or so. By day 7 we almost had to chip the top layer a bit to pull the sticks out. We've made this and had it fail too. If by day 3 (4 at the latest) you don't see any growth, go ahead and heat the syrup up and try again. The fact that your syrup is hardening a bit is a good sign that you used enough sugar. I know you can make it with string too instead of wooden skewers. I'm not sure about the lollipop sticks. Good luck! 🙂
Julie W says
We put our skewers through unbleached coffee filters to keep the dust and pet hair out of our jars but allow for evaporation. It seemed to work well. Also, when we made this during a high humidity period it was a complete failure (but still fun.)
Lindsay McClanahan Jackson says
We used to do this when I was a kid, but instead of skewers we used string.
Brandy says
My son is making some for cubscouts right now with string! Works the same! 🙂
alyssa says
smart idea and im sure it tastes good imma do it in class for an expirement!!!!!!!!!!!!! XP
alyssa says
😛
mamajamie says
We tried several years ago to make rock candy without success. We'll give it a try with your recipe.
mamajamie says
We tried several years ago to make rock candy without success. We'll give it a try with your recipe.
Kierst says
oh my goodness. It's like you were reading my mind! I came to your blog today, specifically looking for this exact post! I'm totally weirded out.
Brandy says
That's funny! Stacy and I do things like this all the time. It must be the Whitaker genes 🙂
ba78370e-ebee-11e2-87d5-000bcdcb471e says
adult candy
Wilma Flintstone says
How would you go about adding flavor please?
Brandy says
Wilma,
I would just add a few drops of flavoring to each jar/glass before putting in your stick.
jamix3fiasco says
Just a thought, it seems like the darker colors did better. Maybe attracted more sunlight. Yellow and pink seem to be smallest and are also the most translucent.
Brandy says
That is interesting and did seem to be the case with ours!
Robert Braun says
This comment has been removed by the author.
Robert Braun says
This comment has been removed by the author.
Robert Braun says
I love this activity. I have 3 daughters and we made this one of the nights events during a 12 girl sleep over. I used the smaller mason jars and labeled each jar with the girls names. I did a test 2 weeks before and found that you really need to have a very good sugar base started on each stick to get the best results. We used the solid food coloring and hard candy flavoring. To help with keeping the bugs away I used some of those outdoor pop up nets you use for outdoor dinners over your plates. The girls loved that they got to see a progress report every evening on their Instagrams. Day seven they were all over after school to collect their rock candy. Thank you
Robert Braun says
3 drops of flavoring is perfect for each jar.
Brandy says
Wonderful! Thank you so much for sharing your experience with making rock candy! And THANK YOU for giving us the right ratio for flavorings. I've had several readers ask about flavoring the candy, but I've only made it with straight sugar for my kids.
Robert Braun says
Your welcome. 🙂