Saturday, November 12, 2011

Crystal Candy

Have you ever seen a crystal and wondered "Where did that come from?" I know I have. This weekend Rachel and I put together an experiment (one that is old, tried and true) that helps demonstrate the idea of crystal growth.

Of all the old-fashioned candy, rock candy is one of the most popular. It is uncommon to find someone who has never tried rock candy.

This lab uses:
Wooden Skewer
Tall, thin glass
1 Cup Water
2.5 Cups Sugar

Step One: Attach the clothespin to the skewer and hang across the top of the cup. Have the end of the skewer about 1 inch from the bottom of the cup.

Step Two: Bring the water to a rolling boil. This means, boil the water so there are tons of little bubbles! (Keep the stove on, you will have it boiling the whole time.)

Step Three: Add 1/4 of the sugar to the boiling water. Stir in the sugar so it dissolves.

Step Four: Slowly add the rest of the sugar, 1/4 cup at a time. Continuously stir so the sugar dissolves. Add the sugar until you no longer have any or the sugar stops dissolving. This may take a while.

Step Five: Take the sugar solution off the heat and allow to cool. (You have now created a supersaturated sugar solution!)

Step Six: Dip the end of the wooden skewer in the sugar solution, then roll the end in some sugar. This creates a 'seed' for the sugar crystals to grow on.

Step Seven: If you want colored rock candy add in food coloring. You want the liquid to be dark enough that it will have a color after the crystals form.

Step Eight: Pour the sugar in the cup.

Step Nine: Put the skewer on the clothespins in the cup. Make sure the skewer is not touching the bottom or the sides of the cup.

Step Ten: Allow the crystals to grow! Update: Let your crystals sit until they start forming around the skewer. The first time we made ours they instantly started growing and in 4 hours were done. However the second time we tried they did not crystallize for a few days. This difference can be caused by the amount of sugar used or the time the solution is let sit and cool before being poured into the cup.
When you take the skewer out of the cup, give it a few minutes to dry. Then enjoy your beautiful crystals!
Lab variables to try: flavoring and other colors

*An explanation of this lab will be put up after this. In that post there will be picture of our rock candy. We accidentally left ours for a day and the whole cup crystalized!*



  1. Thank you so much for this project with pictures of the step-by-step process. This is going to help my daughter tremendously for her Science fair project. Glad I found it!

    1. We are very happy that you like our blog. We hope your daughter's experiment goes well. Ours had a couple mistakes and took a few times to get it right. Don't worry if it doesn't work the first time: Science is about trial and error! Good luck!


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