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How to Make Rock Candy

Updated on May 6, 2011

Rock Candy or Sugar Crystals

Rock candy is made from sucrose, which is table sugar. Usually you use granulated sugar, but you can experiment with brown sugar or specialty sugars. Making your own rock candy is a great way to grow your own crystals, plus you get to eat what you make. You can add colors and flavors or make crystals of pure sugar.


Photo: Douglas Whitaker

What Is Rock Candy?

In its simplest form, rock candy is crystalline sucrose, or sugar crystals. It is one of the first candies ever made. If you look closely at granulated table sugar you can see that each crystal is a tiny rectangular box. This is the shape taken by the monoclinic crystal structure of the sucrose. When you make rock candy, you are making giant sugar crystals, with boxes stacked on top of each other.

Make Rock Candy

Let's Grow Sugar Crystals!

Rock candy isn't difficult to make, but the sugar solution will be heated, so adult supervision is recommended.


Materials for Rock Candy

  • 2-4 cups sugar

  • 1 cup water

  • food coloring (optional)

  • flavoring (optional)

  • rough cotton string

  • clean jar or glass

  • pencil or butter knife

  • saucepan and stove

Instructions

  1. Pour the sugar and water into the saucepan. Start with 2 cups of sugar. Add food coloring if you want colored rock candy.

  2. Heat the mixture over medium heat, while stirring, until it just comes to a boil. Add more sugar until it stops dissolving.

  3. Try to avoid letting the mixture (called syrup) get hotter. Keep it near-boiling and stir until the sugar dissolves. This is when mixture becomes clear, without crystals floating in the liquid.
  4. Remove the pan from the heat. Stir in a few drops of flavoring, if desired. Set the pan in the refrigerator to cool for about 15 minutes. You want the mixture to be room temperature or cooler before pouring it in the jar.
  5. Dampen the cotton string with the syrup mixture. Roll the string in dry sugar. Shake off any excess sugar.
  6. Tie the string to a pencil or knife so that you can rest the pencil on top of a clean jar with the string not touching the sides or bottom of the container.
  7. Pour the cooled syrup into the jar and add the string. You can cover the top with a paper towel, coffee filter, or piece of waxed paper.
  8. Allow the jar to sit undisturbed for 3-7 days. Remove (and eat) any crust of sugar that forms on the top of the liquid.
  9. If you see a lot of crystals start to form on the sides and bottom of the jar, carefully remove the string and set it aside. Reheat the syrup to dissolve the sugar. Cool the sugar syrup below room temperature and then pour it into a clean jar (cool it to prevent it from dissolving crystals already on your string). Hang the string in the liquid.
  10. Remove the crystals when you are satisfied with their size.
  11. You can eat the rock candy immediately or you can hang the string and allow it to dry.
  12. Store rock candy in a dry, sealed container. The candy will stick to itself, so you may wish to wrap it in waxed paper or coat it with confectioner's (powdered) sugar.

See How to Make Rock Candy

Troubleshooting Common Rock Candy Problems

What to Do When Crystals Won't Grow

The most common reason why rock candy crystals won't grow is not having enough sugar in your solution. If you don't get crystal growth within a week, reheat the solution to boiling. Add more sugar until no more will dissolve, then try again.

Certain flavorings will inhibit crystal growth. Fruit juice and sweetened flavorings will inhibit crystal formation. The acid and other sugars in these flavors breaks apart the sucrose (sugar) molecule. The best flavorings for rock candy are oil of peppermint, oil of cinnamon, and concentrated fruit flavors (sold with spices).

If you can, try to grow your crystals in a cool, dry location. A warm spot will speed evaporation of the solution, but it prevents crystals from growing because warm water won't give up dissolved sugar.

You Can Color Rock Candy (Andreas Praefcke)

You Can Color Rock Candy (Andreas Praefcke)
You Can Color Rock Candy (Andreas Praefcke)

Cinnamon or Peppermint Rock Candy Recipe

This recipe takes 1-2 hours to make and yield 2 lbs of candy. This type of rock candy doesn't form sugar crystals, but if you want rock candy quicker than a week or you are having trouble with the traditional recipe, this might be a good option for you.

Ingredients

1 cup water

3-3/4 cups sugar

1-1/4 cup light corn syrup

1 teaspoon red food coloring (or green for mint)

1 teaspoon cinnamon oil (or use oil of peppermint or mint)

1/3 cup confectioner's sugar

Directions

  1. Line a 9" x 13" baking pan or a cookie sheet with foil or waxed paper. Butter the paper or foil.

  2. Mix the water, sugar, corn syrup and food coloring in a saucepan.

  3. Heat the mixture to boiling over medium heat.
  4. Cover and cook for 3 minutes to dissolve sugar crystals.

  5. Uncover the pan and continue cooking over medium heat, not stirring, until a candy thermometer reads 300°F (hard-crack stage). This wil take about 25 minutes.

  6. Remove the pan from the heat.

  7. Stir in the cinnamon or mint oil.

  8. Immediately pour the mixture onto the buttered pan.

  9. Allow the candy to cool completely, about 45 minutes.

  10. Break the candy into pieces.

  11. Coat the pieces with confectioner's sugar to prevent sticking.

  12. Store the rock candy in an airtight containter.

Why Do You Grow Rock Candy?

What is your main reason for making rock candy?

See results

Reader Feedback

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    • profile image

      anonymous 8 years ago

      that was sonme delicious rock candy!=)

    • profile image

      anonymous 8 years ago

      yum

    • profile image

      anonymous 8 years ago

      These directions are harder than others I've found. Why shouldn't I let it get hotter while dissolving and why does it have to cool before pouring into the jars?

    • profile image

      anonymous 8 years ago

      Sweet! Aww man, anyway thanks for the delecious help! Lol! ; )

    • Azareal profile image
      Author

      Azareal 8 years ago

      I added the extra information to help prevent potential problems. If you overheat the solution you risk making hard candy rather than growing crystals. You want to cool the solution before putting it in the jar for two reasons. The first is to minimize the chance of burning yourself. The second reason is because the solubility of sugar is dramatically affected by temperature. You have a much lower chance of dissolving any seed crystals or other pre-existing crystals you may have if you add a cooled solution.

      [in reply to Flint]

    • profile image

      anonymous 8 years ago

      hi I like crystal candy

    • profile image

      anonymous 8 years ago

      i <3 rock candy

    • profile image

      anonymous 8 years ago

      YAY CANDY!

    • profile image

      anonymous 8 years ago

      Im making rock candy for my friends and family....and i make candy but not rock candy yet. so that is what im doing to day. My sister is doing a sci far so im helping her with that.

    • profile image

      anonymous 8 years ago

      my science fair project is asome

    • profile image

      anonymous 8 years ago

      its preety good candy........im doing a sci fair on it in like ..... a week!!!!!!

    • profile image

      anonymous 8 years ago

      i am doing a sciene fair over it and it is so cool to make!!!!!

    • profile image

      anonymous 8 years ago

      i love rock candy i wonder who came up with rock candy

    • profile image

      anonymous 8 years ago

      rock candy is cool i am gonna make it

    • profile image

      anonymous 8 years ago

      holy pooo face it is good

    • profile image

      anonymous 8 years ago

      I WANT 2 MAKE THIS !!!!

    • profile image

      anonymous 8 years ago

      This is soooooooo good i am gunna make sume right now the only thing that sucks is that it takes ages it seames to harden

    • profile image

      anonymous 8 years ago

      CANDY!!!!!!!!CANDY!!!!YAY..... . .. . yay?

    • profile image

      anonymous 8 years ago

      can i use sock string for this

    • profile image

      anonymous 8 years ago

      man u guys get worked over candy ok it iz gud i luv it but im not going 2 go nuts over candy

    • AppalachianCoun profile image

      AppalachianCoun 8 years ago

      I enjoyed this lens tremendously. This is a lost art.

    • profile image

      anonymous 8 years ago

      mmmmmmmmm (mc donalds theme song) YA! I LUVIN' it! YYYYYYYAAA!!!!

    • profile image

      anonymous 8 years ago

      might taste a little "cheesy", but should be fine :P[in reply to herman]

    • profile image

      anonymous 8 years ago

      OMG im so glad i found this site i wanted to grow just crystals then i saw this site and i wanted to do this and see if my teacher will let me pass it around the class room

    • profile image

      anonymous 8 years ago

      this is awesome thx!

    • profile image

      anonymous 7 years ago

      [in reply to sam] WELL ITS SOMETHING WERE U HAVE FUN THE SUGER GETS STICK AND HARD AND IT GET ON THE STRING AND IT GETS LARGE AND BIG AND THIK O YEA

    • profile image

      anonymous 7 years ago

      sexy rock candy RULES !!!!!

    • profile image

      anonymous 7 years ago

      can you youse the mix of the candy more than once

    • profile image

      anonymous 7 years ago

      I LOVE rock candy! Ive always wanted to know how to make these!

    • profile image

      anonymous 7 years ago

      Rock candy is awesome!!!!!!!

    • profile image

      anonymous 7 years ago

      wow i love this rock candy yum!!!

    • profile image

      anonymous 7 years ago

      Brilllant I Will use this for my homework

      Love It xx !!

    • profile image

      anonymous 7 years ago

      THIS HELPS ME FOR MY SCIENCE PROJECT!

      SO MUCH!

    • profile image

      anonymous 7 years ago

      I <3 ROCK CANDY x]

    • profile image

      anonymous 7 years ago

      â¥â¥â¥Hey, im doing rock candy for my science this will help soooooooooooooo much!!! thx luv ya!! â¥â¥â¥

    • profile image

      anonymous 7 years ago

      Wow, this project is amazing! I'm using it for my science fair and my teachers can't wait to see what it looks like! I used this as my resource and thank you so much for posting this, I can't tell you how helpful this was to me (and my science fair grade;) ) You should post other fun candy experiments also! thanks again and great work! ;)

    • profile image

      anonymous 7 years ago

      im doing a project for science class on topaz thx so much!! this'll really help

    • profile image

      anonymous 7 years ago

      @anonymous: ME TOO!!!!

    • profile image

      anonymous 7 years ago

      Works great! My science class is learning about crystal growth, they love it!

    • profile image

      anonymous 7 years ago

      I am learning about crystals 2 i so agree

    • profile image

      MartinPrestovic 7 years ago

      Looks like it would be fun to make with the kids. Is there a way to shape them into balls so they are like lollipops? Guess this means I will have to do some experimenting first until I get them right.

    • delia-delia profile image

      Delia 6 years ago

      Hello from a Squidoo Greeter! I thought I have left a comment before so when I looked I thought, wow I have never seen so many anonymous comments on one lens before! nice lens and I will be making my own rock candy.

    • Sylvestermouse profile image

      Cynthia Sylvestermouse 6 years ago from United States

      This looks like a lot of fun! I am definitely going to try it. Thanks!

    • Oldfashionedcan profile image

      Oldfashionedcan 6 years ago

      This looks really fun. Thanks for sharing.

    • profile image

      WriterBuzz 6 years ago

      This is a great lens. Thanks for making it. Very informative. I gave you a thumbs up

      cause I like your lens.

    • profile image

      anonymous 6 years ago

      @MartinPrestovic: Maybe try rolling a pipe cleaner into a ball and hanging it on the string. :)

    • profile image

      anonymous 6 years ago

      Thanks for this comprehensive lens.

    • Bella Stella profile image

      Bella Stella 6 years ago

      I love candies! I am going to make the ones you proposed...at least it will save me much money!

    • pd6914 profile image

      pd6914 5 years ago

      Haven't had this in years. I should make some! Thanks for the lens.

    • profile image

      anonymous 5 years ago

      This was really good feedback . Thank You for the information ! I'll try making this for the family for the christmas season (:

    • TheJVilleKid profile image

      TheJVilleKid 4 years ago

      I love rock candy! Awesome lens!

    • texan203 lm profile image

      texan203 lm 4 years ago

      Great lens. I will have to try making some!

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