Grow Your Own Rock Candy




About: I have a lot of hobbies and interests. Wood working has recently become one of them. I hope to contribute to the Instructables community!

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!

Step 1: 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

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

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

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

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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89 Discussions


Question 3 months ago on Step 5

This doesn't look right to me. It's been like 4 days. Any advice?


3 years ago

Sugar wont stick to skewer it floats right off of it.


5 years ago on Introduction

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

1 reply

Reply 4 years 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.


6 years ago on Introduction

How much "Pure Lemon Extract" and "Maple Extract" would this recipe need? The 2 flavors would make seperate candies.

2 replies

Reply 4 years ago

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.


Reply 4 years ago on Introduction

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 V

8 years ago on Step 4

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.

6 replies
Max-anBSaturn V

Reply 4 years 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. ;)

JBarker09Saturn V

Reply 8 years ago on Step 4

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.

Saturn VJBarker09

Reply 8 years ago on Step 4

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!

SockPunkySaturn V

Reply 4 years ago on Step 4

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)

beehard44Saturn V

Reply 8 years ago on Introduction

decant it into a new glass when it grows in the side
you can break it up and eat the crystals


Reply 6 years ago on Introduction

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.


4 years ago on Introduction

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!

2 replies

Reply 4 years ago on Introduction

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


Reply 4 years ago on Introduction

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