The burning of limestone to produce lime was probably first undertaken in the Yorkshire Dales in the medieval period. The construction of castles and manor houses, monastic buildings and bridges, required copious quantities of lime mortar and limewash to be available close at hand. Lime kilns were erected to meet this demand. These early examples are called sow (or clamp or sod) kilns and may have been used from the Anglo-Saxon period when stone buildings needed mortar. They consist of penannular earthworks, and there is an example at Pendragon Castle that relates to its original construction in the 11th or 12th century. Read more about the excavation of the Pendragon Castle kiln here.
The earliest hard evidence of lime burning using stone-built kilns within the Dales dates from the early 17th century. A bye-law in Giggleswick, dated 1602, forbade the building of any lime kiln within the township, and a legal document from 1617 referred to various properties in Arncliffe, including a small paddock called Lymekiln Croft which still exists at the western end of the village. A will, attested in 1621, for Henry Holmes of Hebden in Wharfedale lists among his possessions “one lyme kilne and turves” to the value of 12 shillings (60 pence).
The use of lime gathered pace during the later 16th and through the 17th centuries as land began to be taken in from moor and waste for more intensive agricultural usage. The growth of population and economic revival that followed on from the restoration of the monarchy after the Cromwellian interlude led to the great rebuilding of houses in stone and to a desire for increased farm output. Landowners and tenants alike saw their land as a means of generating income but, first, it n eeded improving.
In their natural state, even where the underlying bedrock is limestone, soils across the Dales tend to be acidic – soupy to the farmer – with low levels of nutrients but high moisture levels and they were rather heavy to work. Whatever might grow in these soils provided little benefit to sheep or cow, nor thus to people. To bring such soils up to productive pasture or cultivation involved draining the land, paring off existing growth so it could be burned off, with the resultant potash being slowly washed into the soil by rain. Only at the end of this lengthy process was marl or burned lime – quicklime – added to the soil.
Though there were local variations, the accepted way of doing this was to lay the quicklime in small heaps across the field, sometimes covered in soil. These were left to stand to allow rain water to slake the lime, making it more readily absorbed by the soil. Ever so slowly calcium in the slaked lime was released into the soil, sweetening it by reducing acidity levels. Lime in itself is not a fertiliser, but instead acts as a catalyst for fertilisers. Lime fixes ammonia in the soil and limits the negative effects of nitrates. It helps to aerate the soil, thereby increasing microbial and minibeast activity in recycling nutrients; it makes the soil more easily worked; and it releases calcium, an essential element of plant growth, into the soil.
By the middle of the 18th century, lime was in widespread use for reclaiming waste and for improving existing land, as well as for mortar and limewash. In addition it was used for a host of small-scale industrial purposes, such as tanning, textiles, soap and paper making, that took place in villages across the area.
Up to this time lime kilns were small and simple in concept. Indeed, the design and technology of a late 17th century kiln were little different from a medieval or Roman kiln. Recent field research in the National Park has identified a number of early kiln sites, recognisable by their surface form. They show up as low circular earthworks, usually with a diameter of about 2 metres, surrounded by a low bank, with a narrow neck or funnel leading into the central bowl. They are rarely more than 1 metre deep and most are built into the slope, below small surface quarries or a natural scree slope.
None of these sod, or sow, kilns have been excavated in the Dales so our understanding of them is based on work carried out elsewhere, and is necessarily limited and preliminary. Work is continuing into the location and form of sow kilns in the area. They operated in much the same way as a traditional charcoal clamp. Alternate layers of fuel and small stone were stacked, the whole mass being covered over with turves, and allowed to slowly burn through. The clamp was then dismantled to retrieve the burnt lime. Two such sites lie adjacent to a small bridge where Oddies Lane in Chapel le Dale crosses a small beck.
An archaeological excavation near Ingleton in 2003 discovered a buried 17th century lime kiln of unusual design. It was in perfect condition and consisted of a bowl nearly 1 metre deep and 2 metres in diameter, very carefully constructed with courses of sandstone blocks and a horizontal flue or stoking hole on one side. When this kiln was last used it was filled with stone and fuel, the firing process was initiated, but it was then abandoned and never emptied.
In the 18th and early 19th centuries kilns became more sophisticated with a stone-built superstructure. More than 800 such field kilns have been identified across the Dales. Some are small and simple in design, quite crudely built, and 2 to 3 metres high, but others are more substantial structures 5 or 6 metres high. They were mostly built in response to a huge increase in demand for lime as swathes of moor and fell were carved up into new fields in the Enclosure Movement of this period.
All such kilns operated in much the same way. Kindling was laid on a grill at the base of the cylindrical, or oval, vertical bowl with alternate layers of fuel and stone being laid on top. Most kilns had a small quarry immediately behind and a ramp so that stone and fuel could easily be tipped into the bowl. Once a kiln had been filled to capacity, the rate of burn was regulated to allow actual burning in the central section of the bowl; hot air from here dried out and heated up fresh stone in the upper third; while that in the lower third slowly cooled down ready to be drawn through the draw hole – or eye – at the base. It was then packed in sacks or barrels or loaded on carts to be spread across nearby fields or despatched to areas lacking limestone. Some kilns were constantly being topped up and drawn in a continuous process. Others were filled up, fired and drawn in one discrete operation, such kilns were worked on an intermittent basis.
Across much of the National Park, most field kilns had a single draw arch and particularly fine examples can be viewed from rights of way at Colt Park near Ribblehead, and on the Dales Way south of Conistone. Some kilns had draw arches back to back or side by side, a good example of the latter can be seen on Sharrow Hill south of Grinton.
As the 19th century progressed demand for lime outgrew the capacity of field kilns, and industrial-scale kilns were built, associated with large quarries.
Lime kilns are an integral part of the built landscape and are important in their own right, while the impact of liming is apparent in the patchwork of enclosed pastures across the National Park.
Contributor: David Johnson
Brock, J (1987) ‘Lime Kilns around Richmond’ The Richmond Review No 10 pp6-21
Cleasby, I (1995) ‘Limekilns in Sedbergh, Garsdale and Dent’ Current Archaeology No 145 pp16-20
Johnson, David (2002) Limestone Industries of the Yorkshire Dales Stroud: Tempus
Raistrick, A (1960) ‘Story of the lime kiln’ The Dalesman Vol 22 pp544-545
White, Robert (1994) ‘Lime Kilns’ North Craven Heritage Trust Bulletin pp5-6
Wright, G N (1967) ‘Lime kilns of the Pennine Dales’ The Yorkshire Ridings Vol 4:4 pp33-35