Coastal Alum Works Project

In September of 2014 Archaeological Research Services Ltd carried out a programme of archaeological work, including excavation, at coastal alum working sites at Boulby, Kettleness, Saltwick and Sandsend. This work was funded by Historic England and administered by the North York Moors National Park Authority.

An assessment in 2014 investigated six scheduled alum working sites that were at risk of coastal erosion within the North York Moors National Park. This assessment identified that the alum working sites at Boulby, Saltwick Nab, Sandsend, Stoupe Brow and Kettleness required further work in order to excavate and record them before they suffered damage due to increasing levels of erosion. The archaeological work was intended to enable the Scheduled Monuments at Saltwick Nab, Kettleness and Boulby to be removed from the Heritage at Risk register and a better assessment to be made at Sandsend, which is currently assessed as ‘Vulnerable’.

Alum is a chemical used as a fixative agent in the textile industry and was manufactured from certain varieties of shale. Alum was initially imported from the continent during the Medieval period, but in 1607 a potential source was identified at Guisborough which meant that it could be produced within the country. Shale quarrying and alum production continued to flourish in the north of England until the mid-19th century when new techniques utilising shale acquired from coal mining became a more prolific industrial process. Approximately fifty alum sites have been identified throughout England, of which twenty-two principal sites were established in North Yorkshire.

A combination of excavation, aerial photography and lidar transcription was used across the sites in order to investigate and understand them better. The work revealed information about the construction and the use, re-use and disuse of the sites. The excavations in particular have helped to understand how the sites functioned with such limited space and how the working environment changed to accommodate this. Carrying out these important investigations has provided valuable insights into how the alum industry operated within what is now the North York Moors National Park and how the sites developed over time. Perhaps more importantly, the work has recorded an important part of Britain’s industrial heritage that would otherwise have been lost to the sea due to the rapid pace of coastal erosion that is affecting the North-East coast.