Tips for Successfully Making Rock Candy




What child wouldn't love trying to make 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.  

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 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!   


Tips for Making Sugar Crystal Rock Candy

1.  USE YARN:  Yarn works better than wooden skewers because of the friction of yarn.  

2.  PROOF SKEWERS:  If you choose to use wood skewers, proof them with sugar water first because they are too slick for crystals to form fast.

3.  USE 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.  BOIL:  Make sure the water is boiling so the sugar will dissolve best.  

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

7.  USE GLASS:  Paper or plastic cups don't work as well.  Use glass.  

8.  STAY 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.  

9.  DON'T TOUCH BOTTOM:  Also keep the string or skewer from touching the bottom of the glass so it doesn't get stuck there, either.

10.  USE CLOTHESPIN:  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.  WINDOW:  Let the glasses of sugar water with string or skewer sit in a window that gets light.  

13:  CHECK:  Regularly make sure crystals aren't growing onto the glass.  

14:  SET:  After you pull out your rock candy, let it set.  You will find it looks even better after it has dried and hardened.  



We found goblets to be good glasses for this experiment.  

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.


I pray this post was helpful to both our CC community and to any others looking for a fun and easy experiment to do with children.  Let us know how it goes!


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