What is a Brick made of?
What is a Brick made of?
Clay and shale moulded and fired until the particles partly fuse — a manufactured rock.
The property that decides whether a brick survives a British or a northern American winter is not strength but water absorption. A brick that soaks up water and then freezes spalls its face off, so bricks are graded for frost resistance and the wrong one used below the damp course or on a garden wall coping fails within a few seasons. Mortar is deliberately weaker than the brick: soft lime mortar lets a wall move and cracks along the joints where it can be repointed, whereas a hard cement mortar transfers the stress into the bricks themselves and destroys them. That is the single most common way historic brickwork is ruined by well-intentioned repair.
Component by component
| Part | Material | Why that material |
|---|---|---|
| body | clay and shale, sometimes with sand or crushed fired brick added | Clay is plastic when wet and vitrifies when fired, so the same material can be shaped cheaply and then made permanent. |
| firing | a kiln run at 900-1200 °C | Above about 900 °C the particles begin to fuse; the temperature sets the strength, the water absorption and much of the colour. |
| colour | iron compounds in the clay, plus the kiln atmosphere | Iron oxidises to red in an oxygen-rich kiln and reduces to blue-grey where oxygen is limited, which is how one clay gives several colours. |
| frog or perforations | the indentation or holes through the brick | They cut the weight and the firing time, and they give the mortar a mechanical key. |
| alternatives | calcium silicate (sand-lime) bricks and concrete blocks | They are pressed and autoclaved or simply cured rather than fired, which uses far less energy but gives a different look and movement behaviour. |
Other building materials objects
- Glass Sand melted with soda ash and limestone — three cheap minerals, floated flat on molten tin.
- 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.
- 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 Brick made of?
- Clay and shale moulded and fired until the particles partly fuse — a manufactured rock.
- What is the body of a Brick made of?
- Clay and shale, sometimes with sand or crushed fired brick added. Clay is plastic when wet and vitrifies when fired, so the same material can be shaped cheaply and then made permanent.
- What is the firing of a Brick made of?
- A kiln run at 900-1200 °C. Above about 900 °C the particles begin to fuse; the temperature sets the strength, the water absorption and much of the colour.
Related pages
- Glass Sand melted with soda ash and limestone — three cheap minerals, floated flat on molten tin.
- 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.
- 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