Candy glass is a a sheet of clear material which is formed by pouring heated sugar syrup into a mold. It does not make terribly appealing candy since it lacks a distinctive flavor other than sweetness, and is sometimes used in candy decorations and displays. Candy glass was used historically for stunts in which people needed to break windows. It is relatively easy to make candy glass at home, as long as you have a sturdy pot and a candy thermometer.
Sugar is a very interesting substance, especially when it is heated. By heating sugar and mixing it with various ingredients, people can change its chemical structure to create a wide range of shapes and textures. Some extremely talented candy makers can actually blow sugar syrups like glassblowers blow heated glass. The sugar can be formed into bowls, cups, and an assortment of other forms. These techniques require advanced skills, but candy glass is relatively easy to make.
In films, candy glass makes an excellent stand-in for a window since it is clear and it will shatter just like a real window. The edges are much less sharp, however, making it safer to work around candy glass than real glass. Candy glass can also be colored with dyes to create a replica of a stained glass window. The major shortcoming of candy glass is that it tends to deform in warm or humid environments, and as a result it needs to be used quickly.
To make candy glass, heat three and a half cups of sugar, two cups of water, one cup corn syrup, and one quarter teaspoon cream of tartar in a heavy pot until it boils. As it reaches the boiling point, most of the water will disappear, creating a very dense syrup. Continue boiling the syrup until it has reached 300 degrees Fahrenheit (148 degrees Celsius) and then pour it into a mold. Be aware that candy glass is brittle, so it is not a good idea to make a single sheet and try to cut it.
Once the candy glass has solidified and cooled, it should be used as quickly as possible. It will attract ants and other insects, and it will be subject to melting in even mild conditions. If you need a glass facsimile for something like a holiday display, you may want to consider more durable alternatives to candy glass, unless you know that the display will be kept cool.
