Glass is basically sand; like the stuff you find on the beach, officially know as silicone dioxide.To the sand they add a soda , officially sodium carbonate not too unrelated to that you wash or cook with. That lowers it's melting point. And they also add lime, as in ancient shells and coral, as a stabilizer.
Other ingredients can be added to get special effects. Lead for brilliance, boron for heat resistance, barium to increase refractibility for optical glass, metal oxides for color (that's why they call it Cobalt Blue) or manganese for decolorization (no one is ever satisfied). But the point is that the simplest of ingredients make one of the most complex materials on earth.
Glass is a remarkable substance, made from the simplest raw materials Glassware can be colored or colorless, monochrome or polychrome, transparent, translucent or opaque. Glass is lightweight, impermeable to liquids, readily cleaned and reused, durable yet fragile, and often very beautiful. Glass can be decorated in different ways and its optical properties are exceptional. Glass comes in many forms. Some forms are glassware as in cups, bowls, dishes etc. Other forms are the glass windows on your house and car. If you hadn't heard by now, Glass is a major achievement in the history of technological developments.
What is Glass? Part 2
What is Glass? Part 3
What is Glass? Part 4