Step 1: Ingredients
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
Step 2: Cook the Candy
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 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
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
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.