A lime kiln is a furnace in which limestone is burnt at high temperature. During burning, carbon dioxide escapes from the stone and quicklime (calcium oxide) is left behind. This burnt lime is the raw material for lime mortar, lime plaster and limewash. The lime kiln is thus a key link in the traditional production of building lime.
How it works
Limestone (calcium carbonate) is heated in the kiln to about 900 degrees. At that temperature the stone splits into quicklime and carbon dioxide; this process is called burning or calcining. The quicklime is then slaked with water outside the kiln to make slaked lime, the workable form. There are different types of kiln:
- Field kiln — a simple, temporary stacked kiln in which limestone and fuel were layered and burnt once, in a batch
- Shaft or ring kiln — a masonry kiln that could burn continuously, with a higher and more even output
Application
Lime kilns were indispensable for centuries wherever limestone or shells were available. Many historic lime kilns survive as industrial heritage, and some are listed monuments.
Points to note
- The properties of lime mortar and lime plaster trace back to this burning process
- Quicklime reacts violently with water — historically a hazardous step
Related terms
- Lime
- Slaked lime
- Lime mortar
- Binder
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