Something looks quite odd when looking through the glass of old cathedrals, especially stained glass. It seems quite strange that the panes of glass are thicker at the bottom than at the top. At school, we were taught that all matter should be divided into solids, liquids and gases. The question is however, is glass a solid or a liquid? Some examples of solids include crystals like sugar and salt, where the atoms are all lined up in a row. Liquids on the other hand do not possess this structure.

What about glass? It looks like a solid, nevertheless panes are thicker at the bottom, so does this mean it is a liquid? The answer is that it is neither a solid nor a liquid, it is an amorphous solid. The process of how glass is made is crucial to its structure. When glass is made, the material is quickly cooled from the liquid state. However, it does not solidify when its temperature drops below its melting point. It is now in a state between solid and liquid called a supercooled liquid. This supercooled liquid is cooled further to form an amorphous solid.

Past the glass-transition temperature the movement of the molecules of the material’s atoms have slowed down nearly to a stop. This material is now glass. While the structure does not resemble that of a crystal as it did not freeze, the structure is still more organised than that of a liquid. This is why certain stained glass in cathedrals give the appearance that they have sagged while others do not portray such sagginess. It all boils down to the process of the glass making.

One can conclude that glass is neither a solid nor a liquid but an amorphous solid.

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