02｜What is Glass?

It looks like a solid, but it's actually a liquid!!

At room temperature, it solidifies like a solid, but when the temperature is raised, it softens at around 600 degrees Celsius (transition point), and deforms when strong pressure is applied.

At around 1000 degrees Celsius, it becomes a syrupy, molten state.

This is why glass can be processed into various shapes by bending it, inflating it like a balloon, or stretching it like candy.

Compared to metals and other materials, glass is less susceptible to attack by air, water, acids, and alkalis, making it suitable for containers for storing and transporting chemicals and liquids.

However, it is easily corroded by hydrofluoric acid. Many frosted glass patterns or spouts are processed with hydrofluoric acid, a process called etching.

Glass can break if it is suddenly heated or suddenly cooled. There are various reasons for this, but one is that glass has a large coefficient of thermal expansion, so the suddenly heated part expands rapidly, unbalancing other parts and causing it to break.

Flasks and heat-resistant glass are made from materials with a small coefficient of expansion, so they are resistant to thermal changes.

When manufacturing glass, molten glass is formed. If it is cooled at the same temperature, the large temperature difference with the outside air (25 degrees Celsius) will cause it to break naturally.

Therefore, in the manufacture of glass, it is placed in an annealing furnace that gradually cools the glass.

Glass is slightly softer than quartz and harder than orthoclase. The reason diamonds are used to cut glass for Edo Kiriko or to cut the rim of a glass is due to the hardness of the glass itself.

Also, glass is weak against tensile forces but strong against compressive forces. If people stand on glass cups arranged vertically, they are unlikely to break (please be very careful if you try this, as it is dangerous).

However, cups placed horizontally or stacked are extremely weak.

It is important to store cups upright and not to stack them.