There is no clear answer to the question “Is glass solid or liquid?”. In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid. The difference is semantic. In terms of its material properties we can do little better. There is no clear definition of the distinction between solids and highly viscous liquids. All such phases or states of matter are idealisations of real material properties. Nevertheless, from a more common sense point of view, glass should be considered a solid since it is rigid according to everyday experience. The use of the term “supercooled liquid” to describe glass still persists, but is considered by many to be an unfortunate misnomer that should be avoided. In any case, claims that glass panes in old windows have deformed due to glass flow have never been substantiated. Examples of Roman glassware and calculations based on measurements of glass visco-properties indicate that these claims cannot be true. The observed features are more easily explained as a result of the imperfect methods used to make glass window panes before the float glass process was invented.

People who claim that old window panes are thicker at the bottom because of gravity are, of course, wrong. There are stained glass windows in Europe that are hundreds of years old and have not flowed out of their leads. There are also glass objects from Roman times that are still intact, and obsidian (a natural glass) objects from the stone age that are likewise still intact. The reason old glass is thicker or thinner in places is because it was produced using the old crown glass process, which spins the molten glass producing varying thickness throughout the sheet.

The 3 states are Solids, Liquid and Gas

if you inspect really old glass on a window(30 yrs old)

you can notice the the bottom is thicker than the top which shows it can flow and therefore liquid

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