Salt has always been a valuable commodity and long before there was ever a town called Boston the people who inhabited its fenlands were engaged in extracting salt from the sea. There is evidence of salt-making going back to the Iron Age and its production didn’t stop until the early seventeenth century, more than 1,600 years later.
The most obvious remains are the mounds of discarded silt in such places as Bicker and Quadring that now grow crops and mark where the old salt workings were during the medieval period. It was a vast enterprise. Monasteries played a big part in Lincolnshire salt making. Many acres of rolling fields created by the discard from this industry can also be seen around Wrangle. These hills are known as tofts, in an otherwise flat landscape. At one time they would have been even higher, but intensive agriculture has reduced their height over the years.
A site where salt was made was called a saltern and the process comprised three main parts:
- The first was to collect salt-rich mud from the shores and estuaries after the spring tides
- This salty mud was placed on top of a bed of turves and peat. Water was poured in and a pipe took the filtrate to a clay-lined collecting tank.
- Finally, salt was produced by evaporating this brine in lead pans over peat fires.
Where possible water was used to aid the filtration process through turves or peat as this dissolved the desired sodium chloride. Some unwanted salts such as Epsom Salts remained. The desalinated silty mud was then taken away and discarded in spoil heaps. The huge volume of waste silts indicates the industry’s large scale. Even today dark areas of soil caused by ash from the boiling process can still be seen in the fields in the Borough.
In the Iron Age and Roman periods and into the eighth-century, salt was made in a much simpler way, as is evidenced by Saxon archaeology at Fishtoft.
- Firstly peat was dug, dried and transported on to the site for fuel
- Clay was then excavated and made into pans or troughs
- Brine was collected from entrapment ditches and transferred to settling tanks to allow sediment to fall out
- The final process was evaporation in a line of clay troughs placed over hearths burning peat
- The resultant salt was moved either in carts, or by boats.
Until about the mid-fourteenth century there was a considerable export trade in salt from Boston and other Lincolnshire ports, after which cheaper salt began to be imported.