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.
somu sekhar says
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Bug's Mom says
What an awesome experiment/recipe to try with my kids! I'm curious... Has anyone tried flavoring their syrup with any sort of extracts? I would love to try it, just not sure how much to use. I guess that's why it's an "experiment"! 🙂
Brandy says
So many people have mentioned flavoring it, but haven't reported back to say if they've tried it or not! I don't see why it wouldn't work! Maybe try different amounts in each glass! Have a great week!
kprevite says
We used food flavoring that we bought from getsuckereddotcom and it tastes amazing! Our personal favorite was Blue Raspberry 😀
Brandy says
Great tip, thanks!!
PK Nugent says
What if I used way too much sugar and after a day it looks almost solid?
Brandy says
Hmm...I'm not sure. If after another day or two you don't see any growth, you might try pouring it back in a pan, add a bit if of water to dilute it and reheat it to make the syrup again. I'd just hate to see it go to waste! I would still wait at least a day though.
Orah says
I made these, they seem to have turned out fine- except for the fact they are completely stuck to the bottom on the jars! I atacked a couple with a knife and ate a small peice. Is there any way to get the lumps out without melting the whole lot?
Brandy says
Oh no! The sticks may have been a bit too close to the bottom of the jar, but it sounds like they grew a decent size for you! I'm not sure how to break them out without breaking the candy. Ours didn't hit the bottom. Crystals grew along the bottom, but they weren't attached to the wooden stick. I'm so sorry!
Orah says
It's not too terrible, two candies came out perfectly, another one fell apart and the last 2 are stuck. I'll try holding them over steaming water and hoping they come out all right. The broken pieces I managed to chip out are so pretty and sparkly, I love looking at them in the light before eating them haha
Olgun sohbet Odaları says
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Br St says
Wow! A classic boiled sweets recipe!They look fabulous, good job!
Brandy says
Hi Aryn! I honestly have no clue since I have only made it in the summmer/early fall. Sorry I couldn't be of much help :/
snacks and pickles online says
Totally Awesome
Aryn says
I have a question! I would like to make these for my daughter's winter wonderland birthday party, but I'm worried it might be too cold now. We have only north-facing windows in our apartment with no direct sunlight. Would there be enough light that way, or would it be too cold for the crystals to grow in our window sill? We're in MN and temps have been between 20-40 most days.
Julie Baugh says
Brilliant idea - hoping to give this one a go this holiday.
Unknown says
I wonder how well it would work to use koolaid powder as flavoring& coloring
Our Pinteresting Family says
Love this! I remember doing this when I was a child. 🙂 Megan
Our Pinteresting Family says
Love this! I remember doing this when I was a child. 🙂 Megan
andrea says
Hello there, thanks for the post. Our family is doing this for our summer bucket list!
Just an observation: folks don't hold yourself to any particular timeline. We didn't start to see crystals forming until about day 7. Here we are at day 14 and we pulled one out and it is similar to the smaller one pictured. We have decided to wait another week to see what more we can get.
I knew we had something within the first three days though, because crystals started forming in the top water line and at the bottom of the glass. If you don't have these crystals within the first 4-5 days, you probably need more sugar.
I covered the tops loosely with cupcake liners. I just slipped them over the top through a small hole in the bottom. I too was worried about critters. It also stopped prying eyes from trying to touch.
The LemonDrop Tree says
I'm selling the ball end sticks that are used to make rock candy. They are SO HARD TO FIND!!!! Anyone needs them can contact me at [email protected]