With summer here and knowing that moms are looking for fun activities for kids, I decided to share how we make rock candy! This is an oldie but goodie post here on Gluesticks (originally posted in 2011).
Homemade Rock Candy is incredibly easy to make, it just takes patience. There are so many variations using string, sticks, etc. We’ve taken bits and pieces of what we found online (and our own trial and error) and here is how we successfully made rock candy at home. My son has some growing in our window sill right now as a little project for Cub Scouts. He used a string and didn’t color his sugar water, but the result is the same as the rock candy we made before. For us, it is more fun to watch the crystals grow than to actually eat it. It’s a beautiful science project and treat all in one. To make rock candy on a stick, follow the directions below!
You will need:
Sugar (lots of sugar)
Food Coloring (concentrated for brighter colors)
Wooden Candy Sticks or Bamboo 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 dry completely and set aside. This gives the sugar a base. Something to stick to when it starts to crystallize.
Mix equal parts of water and sugar in a pot on med-high heat until dissolved. Then continue to add sugar until you have 2:1 – 3:1 ratio. It will get to a point where it won’t dissolve anymore.
The first time I attempted homemade rock candy I used a 2:1 ratio and after 3 days of ZERO growth, I poured it all back and heated each individual glass of syrup over the stove again and added more sugar. I wouldn’t recommend doing that, it was a pain, but I didn’t want it to go to waste! I added a bit more sugar to it and it worked. So that’s why I would suggest definitely a 2:1 ratio and then adding a little sugar at a time until it starts to look a little cloudy. That is the point that it has reached saturation.
We used 8 cups of water and 18-20 cups of sugar and it made a lot. So you can definitely half the recipe or create as little as you like as long as you keep within the same sugar/water ratio. You are making a nice, sticky, sugary syrup. Mix until mixture starts to simmer. You do not need it to a rolling boil or bring it to a certain temperature with a candy thermometer. Easy.
Allow your syrup to cool for a few minutes and ladle into your jars using a funnel to catch spills. It is still very hot at this point. We used the tips that we trimmed off of our skewers and dipped them into concentrated food coloring paste, then swirled the skewer into our hot syrup mixture. You can use liquid food coloring, but I like the paste better. If you’d like to add flavoring, now would be the time to do it. Just a few drops in each glass. We did not flavor ours.
Then attach a clothespin to each skewer (the ones you dipped in sugar and let dry) and place in cup. Make sure the skewer isn’t touching the bottom or sides of jar/glass. They need room to grow. Since our glasses were narrow, one skewer seemed to work out best, but we added two in a few of the colors.
Place your jars in a warm location with lots of natural light. Here they are on day one…you can see that there is a bit of sugar build up from when we dipped them in water and then let them dry in sugar as well as on the bottom of the glass. I had no fear of insects or little fingers messing with them so I did not cover mine. I do not know if covering them would alter the process at all.
Day 3. More crystallization.
Day 5. The syrup is crystallizing on the bottom of the glasses as well.
7 days—DONE! We had a great time watching them grow and sampling the finished product.
In the end, the glasses with 1 skewer did better as they had more room to grow.
If you attempt to do more than one skewer/jar, use a wide mouth jar. The orange glass had two skewers and both turned out GREAT, but a couple of the other glasses with 2 were a bit smaller than the rest of the single skewered glasses.
I held the lollipop over the jar to let most of it drip off and then set it on a cookie sheet to dry. You can also leave the clothespin on and just transfer it to an empty jar to let the excess drip off and let the lollipop dry.
And as you can see in the photo, they didn’t all grow at the same rate. The purple one was the biggest we had. So there are obviously many variables to doing this.
*There will be crystallized sugar in the bottom of your jars/glasses. Just run them in hot water and chip it out with a butter knife. It comes out pretty easily.
It’s been almost two years since I originally posted this method/recipe and I’ve received many positive emails, but a couple of ones that were failures from readers. So I thought I would post a troubleshooting section with tips that I have for success as well as some that I found when I “Googled” it. I know how frustrating it can be when it doesn’t work out (It’s happened to me too) and I always hear, “I tried making that as a child, but it never worked), so there must be a large variance in things that affect the outcome. So here goes…
Make sure your glass/jars are clear and CLEAN.
Make sure your sugar ratio is AT LEAST 2:1-3:1 You may need more depending on how quickly it reaches saturation…
“Mix equal parts of water and sugar in a pot on med-high heat until dissolved. Then continue to add sugar until you have AT LEAST a 2:1 ratio. You can also do a 3:1 ratio. It will get to a point where it won’t dissolve anymore……”
When I said it will get to a point where it will not dissolve anymore, that does not mean that it will be gritty and super thick. It will still look like a clear syrup, but a little cloudy. That is when you will know that it is a saturated ratio. Just make sure you bought extra sugar so that if you get to a 2:1 or 3:1 ratio and it is still dissolving super quickly that you can add a little more.
Place in a WARM, SUNNY location. I made this last batch in September when it was still 80+ degrees. I’m not sure if the time of year has anything to do with it or not.
If after a couple of days you don’t see any sugar settling on the bottom of the glass, it means that there most likely wasn’t enough sugar when you started. Just reheat your syrup to a simmer and add a bit more. Pull your skewers out and just roll the sticky skewers in more sugar and let it sit while you reheat your syrup. Is this frustrating to do? Yep. I know, because I’ve done it before!
I have not tried the following, but I thought if what I’ve shared that worked for me hasn’t worked for you, that maybe something here will help.
No crystal growth
This is usually caused by using a solution that isn’t saturated. The cure is to dissolve more solute into the liquid. Stirring and applying heat can help to get solute into solution. Keep adding solute until you start to see some accumulate at the bottom of your container. Let it settle out of solution, then pour or siphon the solution off, being careful not to pick up undissolved solute. If you don’t have any more solute to use, you can take some comfort in knowing that the solution will become more concentrated over time, as evaporation removes some of the solvent. You can speed this process by increasing the temperature where your crystals are growing or by increasing air circulation. Remember, your solution should be loosely covered with a cloth or paper to prevent contamination, not sealed.
If you are sure your solution is saturated, try to eliminate these other common reasons for lack of crystal growth:
Too much vibration Keep your crystal setup in a quiet, undisturbed location.
Contaminant in the solution The fix is to re-make your solution. The fix only works if you can avoid contamination (won’t work if your starting solute is the problem). Common contaminants include oxides from paper clips or pipe cleaners (if you’re using them), detergent residue on the container, dust or something else falling into the container.
Here are more fun and easy science experiments for kids!