Salt on the Screen: Fen

Explore how the changing landscape of the Lincolnshire fens produced an essential industry

Introduction

3000 years ago, the Lincolnshire fenland would have appeared quite different to the present-day environment. Sea level rise in the Bronze Age created a wide expanse of salt marsh, criss-crossed by tidal creeks. This provided the perfect landscape for salt-making. 

Map Tour

Iron Age Landscape

During the Iron Age (800 BC - AD 42), the salt marshes would have been much more extensive than they are currently.

Iron Age and Roman Salt Production

Producing salt from brine essentially relies on the process of evaporation: the brine is heated until the water evaporates and only the salt remains. While on the continent the heat of the sun was strong enough to achieve this, in Lincolnshire it was necessary to burn fuel to fully evaporate the water.

Briquetage

The relationship between the salterns and other sites is revealed by the archaeological evidence remaining from the salt-making process. Briquetage - the ceramic waste from the salt-making process - is often made of clay material strengthened with organic matter.

Fuel

Fuel is another resource that salt-makers would have struggled to source on the salt marsh. Peat is a likely source of fuel and would have been available on the fen edge. Wood was another available fuel and analysis of ashes from saltern sites confirms this was used.

Roman Landscape

During the Roman period (AD 43 - 409), the salt marshes would have been much more extensive than they are today. However, the extent of the marshes had diminished since the Iron Age (800 BC - AD 42) due to encroaching freshwater areas caused by run-off from higher ground.

Relict plants

Though the land has changed greatly through the Iron Age (800 BC - AD 42) and Roman periods (AD 43 - 409) to the present day, traces of the past remain visible. At Surfleet Lows, a number of relict plant species remain from the salt marshes. These halophytes, or salt-loving plants, would have thrived in the earlier salt marshes, adapting to the conditions over time. A few species, such as golden dock and sea-milkwort, remain today as rare survivors from that earlier time.

Iron Age Landscape

During the Iron Age (800 BC - AD 42), the salt marshes would have been much more extensive than they are currently.

The extent of the salt marshes during the Iron Age can be determined by the location of the most westerly salterns, as at Morton. This location on the boundary of the salt marsh provided easy access to saltwater, but also enabled access to other essential materials from the fens to the west, including fuels such as peat. The need to make use of materials that could not be found on the marsh makes it likely that salt-makers moved back and forth between the salterns on the salt marsh, and settlements located further inland.

Iron Age and Roman Salt Production

Producing salt from brine essentially relies on the process of evaporation: the brine is heated until the water evaporates and only the salt remains. While on the continent the heat of the sun was strong enough to achieve this, in Lincolnshire it was necessary to burn fuel to fully evaporate the water.

Early salterns would have consisted of containers raised over a simple hearth, directly heating the container and the water within. By the late Iron Age (100 BC - AD 42), indirect systems of heating were common, such as that pictured here. These oven-type structures would have indirectly heated the water by channelling the heat from the fire via a system of flues. Examples of such systems were revealed during excavations at Cowbit Wash, which have been radiocarbon-dated to cal BC 185-95.

Briquetage

The relationship between the salterns and other sites is revealed by the archaeological evidence remaining from the salt-making process. Briquetage - the ceramic waste from the salt-making process - is often made of clay material strengthened with organic matter.

The clay these ceramics were made from is likely to originate from the silty clay deposits of the fenland, and not too far from the salt-making site itself. However, the organic matter is often cereal-processing waste, from plants including wheat. As a salt-intolerant plant, wheat could not have grown on the marsh. It is therefore likely that the salt-makers must have been bringing this material to the site from elsewhere, possibly from farming activities on nearby settlements.

Fuel

Fuel is another resource that salt-makers would have struggled to source on the salt marsh. Peat is a likely source of fuel and would have been available on the fen edge. Wood was another available fuel and analysis of ashes from saltern sites confirms this was used.

The ashes of trees such as willow, alder, and poplar show that areas of wet woodland were accessible not far from some saltern sites. Fenland islands, such as Guthrum Gowt, were higher than the surrounding marsh and may have provided a nearby supply.

Roman Landscape

During the Roman period (AD 43 - 409), the salt marshes would have been much more extensive than they are today. However, the extent of the marshes had diminished since the Iron Age (800 BC - AD 42) due to encroaching freshwater areas caused by run-off from higher ground.

This changing landscape forced the salt-makers to relocate eastward towards the coast. Salt-making sites dating from the Roman period were therefore situated further east than the Iron Age salterns, following the edge of the salt marsh and routes of tidal creeks.

Salterns were also vulnerable to flooding from the coast. It is likely that multiple episodes of severe marine flooding eventually made this area of salt marsh impassable and led to the decline of salt-making in the 3rd century AD. 

Relict plants

Though the land has changed greatly through the Iron Age (800 BC - AD 42) and Roman periods (AD 43 - 409) to the present day, traces of the past remain visible. At Surfleet Lows, a number of relict plant species remain from the salt marshes. These halophytes, or salt-loving plants, would have thrived in the earlier salt marshes, adapting to the conditions over time. A few species, such as golden dock and sea-milkwort, remain today as rare survivors from that earlier time.

Sources

Derrett, S. (2019) Prehistoric human-environment interactions in the Lincolnshire fenlands: a geoarchaeological investigation of Willow Tree Fen. [Master's thesis, University of York].

Lane, T. W. (2018) Mineral from the Marshes, Coastal Salt-Making in Lincolnshire. Lincolnshire Archaeology and Heritage Reports Series 12.

Lane, T. W. and Morris, E. L. (eds.) (2001) A Millennium of Saltmaking: Prehistoric and Romano-British Salt Production in the Fenland. Lincolnshire Archaeology and Heritage Reports Series 4.

Morris, E.L., (2007), ‘Making Magic: Later Prehistoric and Early Roman Salt Production in the Lincolnshire Fenland’, in Haselgrove, C and Moore, T. (eds), The Later Iron Age in Britain and Beyond, pp.430-443. Oxford: Oxbow.

Main Map

Use the link below to return to the main map.

Coast

Use the link below to explore the history of salt-making in the coastal region.

About the Project

Salt on the Screen is a University of York Digital Creativity Lab Summer School 2021 project. The project seeks to use interactive digital media to explain and explore historic Lincolnshire salt making. Salt on the Screen was been developed by environmental scientist Dr Katherine Selby (project lead), design researcher Dr Debbie Maxwell (project co-lead); and HCI researcher Alexandra Leigh (project researcher). You can contact the research team and  find out more about the project here .

Salt on the Screen was created with the support of

  • Tom Lane
  • Dave Bromwich & The Lincolnshire Wildlife Trust
  • Tish Cookson & the Dynamic Dunescapes Project
  • CITiZAN