Place a double layer of foil onto a larger cookie sheet (15x10x1) and sprinkle generously with powdered sugar. Make sure you get it all the way to the edges. Set aside.
Add granulated white sugar, corn syrup, and water to a large saucepan and heat over medium-high heat, stirring constantly until sugar is melted.
Stop stirring the sugar mixture and bring to a boil until a candy thermometer reaches 300 degrees. Sugar may be a little tan/brown in color. This can often take up to 30 minutes to come to heat.
Remove sugar from the heat and cool just to 260 degrees.
Add cinnamon oil and red food coloring and mix well until evenly combined. Pour the sugar mixture onto a prepared baking sheet.
Allow candy to cool and harden before breaking with a meat tenderizer. Add more powdered sugar to the top of the candy, which helps the pieces not stick together. Store rock candy in an airtight container.
Notes
Hot sugar can burn skin VERY EASILY and requires extreme caution.
If you can make this recipe when it’s not humid, that’s easier/better.
I use LorAnn Oils, which has all sorts of flavors. I use one of the bottles for this recipe.