Limekiln

A 19th century limekiln

A lime kiln is a kiln used to produce quicklime by the calcination of limestone (calcium carbonate). The chemical equation for this reaction is:

CaCO₃ + heat → CaO + CO₂

Although lime kilns were used in the production of lime mortar in Ancient Egypt and later by the Greeks and Babylonians, the Romans favored instead to produce their mortars from pozzolanic ash.

Lime kilns seem to have come into regular use about the 18th century. The larger stones were used for building but the smaller were burnt to produce lime which was a useful commodity in various ways: it could be spread on the fields, for building purposes or for lime-washing buildings. It was regarded as cleansing and was used not only on farm buildings but often on factories after 1800.
The stone had varying degrees of hardness and therefore took varying times to burn; chalk took about 24 hours and limestone about 60 hours, but the harder stone produced the better product. Lime kilns used many kinds of fuel, including wood, coal, turf or other organic products.

The lime production was sometimes at an industrial scale. One example in North Devon, near Torrington, was made up of four kilns grouped together in a square and it was situated beside the Torrington canal to bring in the limestone and transport away the lime in the days before properly metalled roads existed.

Many examples of lime kilns are found at small fishing ports, also for transportation reasons.

The development of the rail network made the local kilns unprofitable and they gradually died out through the 19th. century.

A preserved lime kiln in London