but not just any rock candy.... This is, boulder candy...
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Materials
Skewer Stick, spoon or something that covers the span of your jar
Step 2: Preparation
Fill your jar with water leaving some empty space at the top. Pour this water into a pot.
Place the pot on the stove over medium heat. Heat until you start to see steam rise off the surface of the water. Now, slowly stir in sugar. Keep adding sugar until vigorous stirring does not dissolve additional sugar.
Next, pour the sugar syrup into a jar. Take care not to allow any sugar sediment to pour into the jar.
Step 3: Make Candy!
Tie a long piece of cotton* string to a spoon, fork, skewer, etc. Then, measure the height of your jar and trim the string to this length. You may need to weigh your string down to keep it straight. For this, you can use anything that sinks in water - but avoid lead.
Place your jar in a place that it won't be disturbed for about a week.
After about a week, pull out your candy! If you don't see any growth within the first few days -- drain the sugar water into a pot, heat it and add more sugar. Also check that your string isn't super slippery.
If ants are a problem, place your jar on a plate of water - then add a few drops of detergent. This makes an ant moat.
Here at instructables HQ -- ants are a problem when it comes to leaving food on the counter.
*Do not use nylon or other synthetic stings as these are too slippery for candy crystal growth. Coarse cotton twine works best, providing locations for crystal growth to begin (these are called nucleation sites).
Step 4: Break Through
My rock candy was left in the jar for too long... So, to salvage - I had to break my jar for the full effect. Wear safety glasses ;)
Step 5: How It Works
By heating and agitating water while adding sugar, a saturated liquid is formed. As the syrup cools and evaporates, the fluid becomes super saturated - meaning the water has more sugar than it can hold. When this happens, sugar looks for a place to escape - these places are called nucleation sites and sometimes called "seeds."
The string provides the nucleation sites for crystal growth. As the water evaporates, more sugar crystallizes on the string - growing the rock candy.