IntermediateTopic 35 of 100Materials & Chemical
Glass
Amorphous ceramic with glass transition rather than melting point.
In depth
Glass is an amorphous ceramic formed by cooling a melt fast enough to avoid crystallisation; softens gradually above the glass transition. Soda-lime for windows; borosilicate for heat resistance; fused silica for optics; fibres for reinforcement. Tempering induces compressive surface stress.
Key points
- Viscosity vs temperature
- Annealing point
- Gorilla-type chemical strengthening
ExampleTempered glass shatters into small blunt pieces.
Glass has no crystal structure, which gives it transparency and a glass transition rather than a melting point, so it is shaped at high temperature.
What is Glass?
Amorphous ceramic with glass transition rather than melting point.
Why is it important to understand glass?
Glass has no crystal structure, which gives it transparency and a glass transition rather than a melting point, so it is shaped at high temperature.
What is the glass transition?
The temperature at which an amorphous material changes from a hard, brittle state to a softer, viscous state.
Why does tempering make glass safer?
Surface compression is introduced, so the glass breaks into small blunt fragments rather than large sharp shards.
How is Glass used in practice?
Typical applications include designing a window pane for a building that must resist wind loads, choosing borosilicate glass for lab glassware that must withstand heat and tempering glass for a car side window to make it break safely.
What should I learn before Glass?
Study "Ceramics" first (topic 34 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Glass?
Viscosity vs temperature. Annealing point. Gorilla-type chemical strengthening.
Can you give an example of Glass?
Tempered glass shatters into small blunt pieces.
What comes after Glass?
The next topic is "Cement and refractories", which builds directly on this one.
How difficult is Glass?
It is classed as Intermediate in Materials & Chemical (topic 35 of 100). It is an intermediate topic. Work through the beginner topics in Materials & Chemical first.