What is a green brick?
A green brick (Dutch: vormeling or vormling) is a piece of clay that has been shaped but not yet dried, and is intended to be fired. For bricks, it is the wet clay block that has just come out of the mould or press. Only after drying and firing does it become a brick.
From clay to brick
- Forming: the clay is thrown or pressed into a sanded mould (hand moulding or machine moulding), or cut from a column produced by an extrusion press. The result is the green brick.
- Drying: the green brick still contains a lot of water and is soft. It must dry slowly and evenly; drying too fast causes cracks and warping. In the past this was done outdoors in drying sheds, today in drying chambers.
- Firing: the dried brick goes into the kiln, historically for example a clamp or ring kiln, today usually a tunnel kiln.
Why sand?
The mould is dusted with sand so the green brick releases easily. This sand also gives the brick its typical sanded surface, which suits facing brickwork. In the past the clay lump was sometimes rolled through sand before being thrown into the mould.
In practice
You mainly come across the term in brick history and manufacture. It helps to explain marks on old bricks:
- Finger or animal prints and plant remains on old bricks were made while the green bricks were drying outdoors.
- Strike face: the struck-off top of the green brick can still be recognised as one different face on a sand-faced moulded brick.
- Distortions often point to handling or stacking while the green brick was still soft.
Related terms
- Brick mould
- Sand-faced moulded brick
- Hand-moulded brick
- Extrusion
- Hoffmann kiln
- Edging green bricks
- Green strength
- Brick
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