How To Make Sugar Crystals Rock Candy

What kiddo wouldn't love making rock candy?!  

Mine were pretty excited to have this as one of the science experiments in Classical Conversations this past school year.  

But my tutors and I quickly learned that this experiment can be quite finicky. 

Here's what finally worked.

I tried both yarn and wooden skewers.

I tried glass and paper cups.

I tried a few measurements of sugar.  

I tried sugar and powdered sugar.  

I tried hot water and boiling water.

I tried sunlight and less sunlight.  

With a lot of trial and error...

my boys and I finally came up with a list of tips for a successful rock candy experiment.  

So successful, in fact, that we've had crystals grow within a day!  

Supplies For Making Sugar Crystal Rock Candy

Yarn or Wooden Skewers

Glass Goblets

Clothespins

3 Cups Sugar

1 Cup Boiling Water

Plastic Wrap

How To Make Sugar Crystal Rock Candy

Boil 1 cup of water. 

Dissolve 3 cups of sugar in boiling water. 

Stir well until sugar is completely dissolved. 

Pour sugar water into glass goblets or cups. 

Place yarn or wooden skewers vertically into center of the sugar water. 

Cover glasses with plastic wrap. 

Suspend the yarn or skewers above the bottom of the glasses with a clothespin rested on top of the cup. 

Put your glasses in a window with plenty of sunlight. 

Check your sugar crystals every day to make sure they aren't growing to the sides or bottom of the glass. 

After about a week, there should be significant crystals grown to the string or skewer. 

Remove string or skewer covered in crystals and let it set on wax paper until dry and hard. 

YAY! You made sugar crystal rock candy!

Extra Tips For Making Sugar Crystals

1.  YARN WORKS BEST FOR CRYSTAL FORMATION  

Yarn works better than wooden skewers because of the friction of yarn. But then again, I'm not sure you'd let your kids eat off yarn, lol. 

2.  SKEWERS WORK WELL FOR MAKING EDIBLE ROCK CANDY, PROOF THEM FIRST

If you choose to use wooded skewers, proof them with sugar water first because they are too slick for crystals to form fast.

3.  USE GRANULATED SUGAR

Powdered sugar didn't work as well for us.

4. RATIO 3 to 1

Dissolve 3 cups of sugar into 1 cup of water. It's a lot, but it works.

5.  USING BOILING WATER

Make sure the water is boiling so the sugar will dissolve best.  

6.  STIR THE SUGAR INTO THE WATER WELL

Sugar incorporates into the boiling water best if you stir it well.  

7.  GLASS CUPS WORK BEST

Paper or plastic cups don't work as well. Use glass. We found goblets work well. Plus, kids can see the progress each day through glass.

8.  KEEP THE SKEWER OR YARN CENTERED

Keep string or skewer in the center of the glass so the project doesn't cement to the sides. You want to be able to remove it from the glass when the project is done.

9.  DON'T TOUCH THE BOTTOM

Also keep the string or skewer from touching the bottom of the glass so it doesn't get stuck there, either.

10.  USE CLOTHESPINS TO SUSPEND THE SKEWERS

Clip the string or skewer into a clothespin to suspend it in the glass without touching the sides or bottom of the glass.  You can see this in the below picture.

11.  COVER IN PLASTIC WRAP

If you plan to let your children eat the sugar crystals, cover the tops of the glasses in plastic wrap to keep out dirt and dust.  

12.  USE A WINDOW

Let the glasses of sugar water with string or skewer sit in a window that gets light.  

13. KEEP CHECKING

Regularly make sure crystals aren't growing onto the glass, or you won't be able to remove them when they are done. 

14.  LET IT SET

After you pull out your rock candy, let it set on wax paper. You will find it looks even better after it has dried and hardened.  

We found goblets to be good glasses for this experiment because clothes pins rest nicely on top,

holding the skewers above the bottom of the glasses.

The left skewer was proofed better than the right skewer.

The proofed skewer obviously grew crystals faster.

This picture was taken less than 24 hours after starting!

The crystal here grew really well on a string that settled in the water as a loop.

The string started growing these crystals almost immediately.

This set for about a week, but had enough crystals after a day.