What is a Glass made of?
What is a Glass made of?
Sand melted with soda ash and limestone — three cheap minerals, floated flat on molten tin.
Flat glass was ground and polished at great expense until Alastair Pilkington's float process in 1959: molten glass is poured onto a bath of molten tin, where it spreads to a perfectly flat ribbon of even thickness because both surfaces are formed by gravity and surface tension. Nearly every window in the world is now made this way, and the tin side can still be identified because it fluoresces under UV. The persistent claim that old window panes are thicker at the bottom because glass flows is false — glass at room temperature is a solid on any human timescale, and old panes vary because the crown and cylinder processes made them uneven.
Component by component
| Part | Material | Why that material |
|---|---|---|
| former | silica sand, around 70-74% | Silica forms the random network that is glass; on its own it needs about 1700 °C to melt, which is impractically hot. |
| flux | sodium carbonate (soda ash), around 12-15% | It drops the melting temperature by hundreds of degrees, which is the only reason glass is cheap. |
| stabiliser | limestone, giving calcium oxide around 10% | Soda-silica glass alone dissolves in water; the calcium makes it durable, which is why the recipe has three parts and not two. |
| cullet | crushed recycled glass, often 20-60% of the batch | It melts at a lower temperature than raw batch, so recycling glass saves fuel as well as sand. |
| variants | boron oxide for borosilicate, lead oxide for crystal, low iron for solar glass | Boron cuts thermal expansion so the glass survives thermal shock; iron is what gives ordinary glass its green edge. |
Other building materials objects
- Concrete Stone and sand glued by cement paste — and it hardens by a chemical reaction with water, not by drying.
- MDF Wood pulled apart into individual fibres, mixed with resin and wax, and pressed hot into a board.
- Road asphalt About 95% crushed stone and sand, glued together by roughly 5% bitumen from the bottom of an oil refinery.
- Brick Clay and shale moulded and fired until the particles partly fuse — a manufactured rock.
- Mirror A sheet of ordinary glass with a microscopically thin silver layer on the back, sealed under paint.
- Plywood Thin wood veneers glued in alternating grain directions — the cross-lamination is the entire idea.
Common questions
- What is a Glass made of?
- Sand melted with soda ash and limestone — three cheap minerals, floated flat on molten tin.
- What is the former of a Glass made of?
- Silica sand, around 70-74%. Silica forms the random network that is glass; on its own it needs about 1700 °C to melt, which is impractically hot.
- What is the flux of a Glass made of?
- Sodium carbonate (soda ash), around 12-15%. It drops the melting temperature by hundreds of degrees, which is the only reason glass is cheap.
Related pages
- Concrete Stone and sand glued by cement paste — and it hardens by a chemical reaction with water, not by drying.
- MDF Wood pulled apart into individual fibres, mixed with resin and wax, and pressed hot into a board.
- Road asphalt About 95% crushed stone and sand, glued together by roughly 5% bitumen from the bottom of an oil refinery.
- Brick Clay and shale moulded and fired until the particles partly fuse — a manufactured rock.
- Mirror A sheet of ordinary glass with a microscopically thin silver layer on the back, sealed under paint.
- Plywood Thin wood veneers glued in alternating grain directions — the cross-lamination is the entire idea.
- Pencil Stationery and paper
- Tennis ball Sport and games
- Banknote Around the house
- Golf ball Sport and games
- Paper Stationery and paper
- Soccer ball Sport and games
Sources
- Typical range compiled from manufacturer specifications — At One Place