Grow Your Own Rock Candy

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Picture of Grow Your Own Rock Candy
Looking for something sugary to satisfy your sweet tooth, and at the same time have something fun to fill your time?  Then try growing your own rock candy!  Often times seen at carnivals, fairs, or theme parks, this sucker will not only taste great, but you'll learn something in the process as well.  Once you try it, and you decide you want to branch out, try some new flavors!  It does take 3 to 5 days to grow, but the end result is a delicious treat that you can impress your friends with!
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Step 1: Ingredients

Picture of Ingredients
I guarantee you have all the ingredients needed to grow your own rock candy at your home already.  If you decide to get a little more experimental, you may want to take a trip to your local grocery store, they'll have everything you need!

1 Cup of Water

3 Cups of Sugar (not powdered, but then again I haven't tried it.)

1 Wooden Skewer (also known as a brochette in the cooking world.)
       If you don't have one, a piece of string and a paper clip will work.

1 Clothespin (I needed two because my glass had a wider rim than I expected)
       If you don't have a clothespin, a paper clip will work.  Or if you're using a string then a          toothpick would work.

1 Pan or Pot, and a stove

Fork or Wooden Spoon

1 Tall glass (A regular dinner glass will work, but do not use plastic or paper)

Those are all the ingredients you really need.  I used some other things as well, but that is because I had done it once before and wanted to try some new things.

1 Cookie sheet

2 Tablespoons of Vanilla

Aluminium Foil

Step 2: Cook the Candy

Picture of Cook the Candy
Pour the water into the pot or pan and turn the temperature on the stove up to High.

If you are using flavoring, add it next.  I used 2 tablespoons of Vanilla, but you really only need 1 tablespoon.  I just wanted a REALLY strong flavor.  You can pick up candy flavoring at any grocery store.  If you don't want the flavor, food coloring also works to add some color.

Before the water comes to a boil, add 2 cups of sugar, and save the last cup for later.

Stir the mixture until the sugar completely dissolves.  If the water reaches a full boil, remove it from the burner and move it to another burner on the stove.  If the water is allowed to boil for too long then the sugar will burn and your rock candy will have a strong burnt taste to it.

Add the last cup of sugar 1/4 cup at a time to the mixture making sure it is fully dissolved before adding more.

Keep an eye out for any sugar that does not completely dissolve.  If you see sugar that will not completely dissolve, do not add any more sugar.

Once you either add all 3 cups of sugar or decide that no more sugar will dissolve, bring the water to a full boil and remove it from the burner.

At it's full boil, stir it until it barely stop boiling and returns to it's smooth look while stirring.

Carefully pour the mixture into a tall glass, about 1/2 an inch to an inch from the top, or until all the liquid is gone.

Step 3: Grow the Candy

Picture of Grow the Candy
If you're using a clothespin and a skewer, position them on the top of the glass so the skewer is hanging approximately an inch from the bottom of the glass, directly down the center.

If you're using a string, attach the paper clip to one end of the string and mount it to the other paper clip or toothpick so it is hanging directly down the center of the glass, about an inch from the bottom.

Place the glass in a place where it will not be disturbed for 3 to 5 days.  Keep checking back on your candy to watch it's progress.  When you feel satisfied with the size of your sucker, carefully remove it from the glass bu pulling straight up on the skewer or string.

If sugar has grown a layer on top of the liquid, carefully chip it away with a knife or fork.

Hang the rock candy above a paper towel or plate to allow the remaining liquid to drip off and dry.


Step 4: The Science

Picture of The Science
Now for the learning part of this delicious treat.  I'm not a professional in the area, nor do I use the most politically correct vocabulary for the subject.  I do however, know enough to explain the basic principles.

Sugar naturally has a crystalline structure, which would be noticed under a microscope with the individual grains.  

A solvent (in this case, water) can only dissolve a certain amount of a solute (in this case, sugar) before it becomes fully saturate.  

By heating the water, it is able to dissolve more and more sugar.  This becomes known as a supersaturated solution.  

We allow the water to absorb the most sugar it can by heating it to it's boiling point of 212°F (100°C), but try to avoid caramelizing and burning the sugar.

As the water cools, it can no longer hold the same amount of sugar we added.  This sugar is "seeded" on the skewer or string, but will not grow on the clean glass surface or perhaps a nylon string or fishing line.  The sugar "regrows" into a crystalline structure.

Step 5: A Note For Next Time

Picture of A Note For Next Time
There are a couple of interesting things that could be tried, though I'm not sure all of them will work.

Instead of using standard table sugar, try using powdered sugar.  I'm not sure if it holds the same qualities in order to grow back or even dissolve as much.

Try different flavors.  Anything from root beer extract to natural fruit zest dissolved in, what ever flavor you fancy, give it a shot!

If you would like to weigh down your string with something other than a paper clip (because lets face it, who wants to suck on a paper clip) try using a lifesaver tied to the end of the string.  Shoot, it's candy already.

Try different shapes.  If you can wind your string around a paper clip in the shape of a heart, this could make a great treat for a loved one.  Maybe spell out letters of your name?  Who knows, the possibilities are endless.

If you have any ideas, feel free to let me know and I'll definitely give them a try!

Hope you enjoyed the instructable.
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CAScreate1 year ago

how long does it take to make these. me and my sister are making them today and we would like to know

Max-anB CAScreate2 months ago
Takes 3 days to 3 weeks depending how well u coat ur surface with sugar and what type of surfactant how well u cooked ur sugar and so forth.
Galahir9502 years ago
How much "Pure Lemon Extract" and "Maple Extract" would this recipe need? The 2 flavors would make seperate candies.
The extracts are great for flavors. I suggest mixing ur sugar solution first then splitting it into two glasses then put 2-3 nice drops in each. U can put more for stronger flavor but for one glass I wouldn't do more than a table spoon. U can also ads ur food coloring at the end so u know which one is what flavor. Best of luck.
JBarker09 (author)  Galahir9508 months ago

The amount depends on how strong you want the flavor. If it comes in a dropper I would use about 5-10 drops, then adjust to your liking.

Saturn V4 years ago
Mine isn't growing on the skewer, it's recrystallizing on the top. Why is this? The skewer was straight down the middle, 1 inch from the bottom.
Max-anB Saturn V2 months ago
Dip ur skewer or string in water then in sugar before u put it in the cooked sugar for growing it provides a good surface to grow on. ;)
JBarker09 (author)  Saturn V4 years ago
I've noticed with mine if they start growing on top, it won't grow on the stick. If i take a fork or something and poke the surface so the liquid is exposed again it started growing. I have no explanation for this, but I hope to find out the answer in my fluid mechanics class this semester at Arizona State.
Ah. Now some is finally growing on the stick, but it's just a very tiny bit. Some of it's even growing on the glass. Darn variables!

chances are that it was crashing out to the top because of dust or other particles on the surface, and that breaking it caused the other molecules crashing out to look for another surface- in this case, your string, but you got less growth because the solution was less oversaturated at that point. (yes, way late comment, but someone else might be having the same question)

decant it into a new glass when it grows in the side
you can break it up and eat the crystals
Pull out the stick and reheat the solution. The crystals on top will go back into the solution and then you can put the stick back in and continue. Once crystals form new crystals will want to connect with them. If you only allow crystals on the stick, that's the only place they will grow.
NoahB45 months ago

why would u need aluminum foil?

MichelleV15 months ago

I love this! I made this into a science fair project. I recorded if the different type of water affected the growth of rock candy. I won 2nd place!

joemonkey4 years ago
i always used Ammonia and Bleach. that makes the coolest colors.

You can eat these you know that right?

JBarker09 (author)  joemonkey8 months ago

Reading back through these comments 4 years later and this reply still made me laugh, and I'm in class right now lol

just kidding. don't do that :)
JBarker09 (author)  joemonkey4 years ago
Gotta admit, I laughed pretty hard at this.
Love how you put some science into this! Very interesting!
JBarker09 (author)  JohnDeere3128 months ago

Thanks! It was my first instructable so I wanted to go all out. I hope to be coming up with more soon!

Vininski2 years ago
I mustn't have boiled it for long enough or something cause mine took a few weeks to grow a decent amount (I also realised after that a metal skewer was not the best choice). Anyway worked a treat, thanks very much!
JBarker09 (author)  Vininski8 months ago

The hotter the mixture is, the more sugar that is allowed to dissolve. You can also try coating the wooden skewer or string with sugar prior to dipping it down into the liquid. Sorry, but metal doesn't work as well because of it's physical properties. Hope it worked out for you :)

punkyc11 year ago

when did you make this?

JBarker09 (author)  punkyc18 months ago

I remember making rock candy like this when I was a child, but this instructable was posted in 2010. Hope you enjoy it!

dallinrp11 months ago
I think mixing honey and lemon juice would be a good flavor.
JBarker09 (author)  dallinrp8 months ago

Honey and lemon juice sound like they would make a great combination!

CAScreate1 year ago


mhettick1 year ago
thanks i needed a rock candy recipe!
Momarabbit4 years ago
Anyone have an idea how to make several at a time for a kids birthday party. If I follow above i would have to use a LOT of glasses. I can't think of how to go about this. Thank you in advance!
JBarker09 (author)  Momarabbit4 years ago
The only thing I could think of would be to use a container such as one used to store cereal that is an oval shaped, taller container. I would say anything that is able to keep them a reasonable distance apart, and that won't melt when you pour the liquid in would work. And when I say reasonable distance, I would think a little more than the diameter of the candy you are making would suffice. Never tried it though. Hope this helped!
Collarina4 years ago
This only make one?
Obediah5 years ago
It would only take a a little bit of effort to give the powdered suger version a test. Maybe it would work, maybe not. Failure is ALWAYS an option. Either way you learn something.
Are you a Mythbusters fan?
i am
definitely, it just seems that everyone is assuming that powdered sugar has starch, and that would make it impossible to grow rock candy. MB has taught me never to take public opinion as wise. $3 and 20 minutes of work and you have your answer, maybe you have something totally better.
BUBBA RAY4 years ago
this is a great project me and the family were doing it right now as i speak great idea
Shany1204 years ago
build524 years ago
sweet!!!!! I can't wait to make it.
Instead of skewers, I use chopsticks.
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