Create a mold for whatever you want to create--be it a window, cup, mirror or other object. Be sure to make your mold ahead of time so it is ready to go (set and dry) as soon as you start making the sugar mixture, because the sugar mixture cannot be made ahead of time, it must be used when mixed. Get your mold all ready, and wipe it down to make sure it is clean so you don't come out with a dirty piece of glass.
Figure out how much mixture you're going to need. Whether you need 2 cups, 2 liters or 5 gallons of fluid will depend upon how large your mold is. Try to estimate the volume of your mold and make an educated guess based on that. Remember, it's always better to have more fluid than not enough, especially when you want everything to look even and perfect, not added later and fragmented.
Place an old saucepan on the stove. Pour in 2 parts water. Turn on the stove's heat to low. Allow the water to heat but not come to a boil. Slowly stir in the 3 1/2 parts sugar. Continue to stir as you pour. The mixture should be somewhat thick now and have a slight water coloring.
Stir in 1 part liquid glucose. Continue to stir. Allow the mixture to come to a low, rumbling boil. The liquid glucose will make the mixture return to a clearer-looking coloring. If you use a syrup instead of liquid glucose, you will be left with a tinted glass, so if you want your glass clear, use only liquid glucose. Let the mixture thicken so that most of the water cooks off.
Pour the mixture into the mold. Tap the mold, or lightly hit it against a hard surface to release any air bubbles and flatten the surface of the mixture to ensure a smooth finish. Let sit in a cool, dark place. Depending on the size and depth of the mold, it should take anywhere from 1 to 10 hours top harden. Gently remove the glass from the mold when ready, and you're set to go!