The salt houses were last used in 1865
"Salt was often said to be worth its weight in gold," says archaeologist Frank Green.
Salt was a booming trade along the Solent coast up to the middle of the 19th century.
Now the secrets of Lymington's salt industry are set to be revealed by Mr Green and a team of archaeologists and volunteers.
The area around the country's last two remaining sea salt boiling houses in the town is being excavated.
The New Forest National Park Authority and Wessex Archaeology is organising the archaeological excavation beside the Lymington-Pennington marshes to establish the size and scale of a typical salt working site.
The salt boiling houses are Grade II listed buildings which will be converted into an office and storage space, once the excavation is finished.
Over 100 volunteers are helping with fieldwork and dives to discover the underwater archaeology of the Solent.
Salt and civilisation
The salt houses are beside the Lymington-Pennington marshes
Salt was a vital commodity - as well as preserving and improving the taste of food, it was used for tanning hides to make leather and for treating wounds.
The New Forest National Park Authority's archaeologist Frank Green said: 'Salt was often said to be worth its weight in gold and has played a vital role in nearly every civilisation since the beginning of time.
"It wouldn't be over-emphasising it to say that you could judge how sophisticated a society was by the availability of salt," he continued.
Salt was made through a process of first drawing sea water into clay-lined trenches where some of the water evaporated.
The brine, which was now concentrated, containing more salt, was then pumped by windmills to tanks outside the boiling houses.
It then entered into large copper or iron boiling pans which were fired by coal brought by barge from the Newcastle area.
As the water was evaporated, the salt crystals could be skimmed off to be dried and stored before being taken out again by barge to ships for transportation.
Evidence shows that at the peak in around 1730 there were 163 pans in the Lymington area.
Between 1724 and 1766 Lymington exported 4,612 tons of salt in 64 ships - 12 cargoes were destined for Newfoundland, 33 to America and others to Norway, Ireland and the Channel Islands.
Although seasonal, it could be a hugely lucrative business when the weather was dry and warm.
Records show that the owner of some of the Lymington salt houses, Mr Charles St Barbe, made a profit of £25,000 - equivalent to £2.2m today - and that was after paying heavy salt taxes.
By the middle of the 19th century the coastal salt production industry died out because of the cost of fuel and because cheaper rock salt became available from Cheshire.
The team are also searching for evidence of salt working on the site from the Iron Age and the Bronze Age as well as investigating the coastal processes of the area and how the Solent was formed.
Frank Green said: "The salt industry once dominated the New Forest coast and has shaped the natural and economic landscape which residents, visitors and nature lovers know today.
"Salt production is one of the oldest industries and has played an important role in human development.
"It's important we find out as much as we can about these before they are lost to climate change."
Tours of the excavations are available as part of the Festival of British Archaeology:
Monday 19 July - Wednesday 21 July: meeting at 1100
Friday 23 July - Saturday 24 July: meeting at 1100
Sunday 25 July: meeting at 1400
Tuesday 27 July - Thursday 29 July: meeting at 1100 and 1730.
Booking essential - contact James Brown on 01590 646695.