DROPS bounce from spike to spike down the blackthorn stacks. Sun glances over them, turning a brush-like wall of twigs into a shimmering curtain of liquid light. The sight is mesmeric. It’s like watching a bush being drenched by the shower, or the fast-melting of water over shrubbery, but this is a bright, dry, December day. What falls here, over this dark, reddish-black brush, is not rain, though, but seawater, collected from the Firth of Clyde, whose shores are just metres away.

These drenched stacks form what’s called a graduation tower, a long, up-turned V shape made out of wood and sticks, whose sole purpose is the repeated running of seawater over thorn, in order to concentrate the brine and gather salt. This monolith on the harbour in Ayr is the creation of Gregorie Marshall, a former architect, who had until last year been primarily an importer of salt, running his family’s century-old business, Peacock Salt. Marshall had long harboured a desire to make salt himself – and was inspired by traditional methods once used in Germany and Poland.

What is remarkable is that Blackthorn Salt is one of only two businesses manufacturing salt in Scotland. We, in this country, are surrounded and awash with salt. Dissolved in sea water, it laps up upon every shore in our convoluted coastline. Before refrigeration, it was a hugely important commodity, vital for the preservation of meat and fish for winter use or sea voyages. Salt played a vital role in our maritime history. The industry was so important to us that in the negotiations for the Act of Union, politicians secured protection of the salt industry. As a result, Scottish sea salt was exempt from a tax applied to English rock salt. In the last 18th century, it was Scotland’s third-largest export, after wool and fish.

Yet, we haven’t had a proper salt producing industry since the 19th century. The last salt pan house, in Prestonpans, closed in 1959. The only other salt manufacturer currently in Scotland is Isle Of Skye sea salt, whose method involves single-stage evaporation in polytunnels.

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Marshall's tower of thorns, he explains to me, works by increasing the surface area of the water so that more evaporates off. “If you’ve got a big bath only the top of the water is where evaporation happens, whereas here we pour a whole bath over the top of the blackthorn and you can get all those little droplets exposed to the air that’s flowing through, so more evaporates.”. Blackthorn, one of the hardest of woods, is particularly suited to increasing this surface area.

“There are so many spikes on it,” Marshall says. “Have you ever picked sloes? They are lethal. You flow the seawater over the top of this and it hits the more points and jaggy bits and makes a bigger surface area which causes more evaporation. We change the speed of it depending on what’s happening in the surrounding atmosphere. If it’s really windy, if it’s not windy or if the sun’s out."

The blackthorn construction is a thing of beauty in itself, but it is also, in a stunning location, right next to the waters of the Firth of Clyde, looking over to Goatfell and the Arran mountains, sitting on a bay in which the wreck of a sunken Puffer, the Kaffir, juts out of the still water. From the top of the tower, Gregorie’s wife, Whirly Marshall, points it out and tells the tale of the Puffer, a real-life farce, rather like a local Whisky Galore, but involving coal. Blackthorn Salt is, in so many ways, all about the tales and the history. It is, like so many artisan products, a story as well as a seasoning.

The process they are using, this graduation tower, is one that was common in Poland and Germany, but has since phased out. While some of the towers remain, they are mostly tourist attractions and health spas. “You go in to them,” Gregorie Marshall says, “and it’s all about breathing in the salty air, all about the salinity, about how good it is for your lungs and respiratory system. They are spa towns. They just keep them running for the atmosphere.” Many believe the mineral-rich water droplets in the air deliver bealth benefits, just as breathing in sea air might.

Marshall came across the towers when he started to explore the idea of producing his own salt and investigate the methods used globally. “I went to see a tower in Germany. A lovely chap invited me across and I stayed in his house with his wife. And he showed me around two or three different towers. I started to wonder, how do we do that over here and will it work? Because over there is done with underground brine, and here is seawater, a completely different thing. “

The largest complex of graduation towers in the world is located in the spa town of Ciechocinek and has three towers at a total length of over 2 km. Though they no longer produce commercial salt, they are kept running as one of the health-giving features of this spa town, famed for its saline springs. The very first graduation towers, developed in the 6th century, used straw.

Marshall experiment with using this blackthorn system with what sat in the Atlantic outside his door. The main question was whether the approach would work as well for seawater as rock brine. He mostly followed the pattern used in Germany – of running the water over blackthorn stacks.

“Blackthorn is what they used in Poland. You go with the history of what they’ve done. Why choose something else? When I first looked at it 15 years ago I thought there must be some new modern material. Plastic? But the thing about this is that you cut the blackthorn and it regenerates and by the time you need it again it’s grown enough. There’s a whole cycle in there. You’re not damaging anything. There’s nothing being lost when you get rid of it. In an ideal world we’ll find something to do with this blackthorn when it’s finished. Maybe by then we’ll have a wood chip boiler. Just chip it all up. The blackthorn should last 7-10 years before it needs to be replaced."

Back in the days when Scotland was a salt-producing nation, our shores littered with pan houses, there wasn’t anything so beautiful, or spa-like about the salt-making process. It was a brutal, grubby, malodorous process that produced a salt that was generally considered dirty. Many other countries produced their salt by mining and, but in Scotland we extracted it using what was to hand here. That was seawater, blood and coal.

Whirly Marshall is now somewhat of an expert on the local history of salt-panning, having extensively researched it. She takes me to see two buildings, which are actually visible in the distance, a few miles up the coastline from their thorn tower. These, she says, are derelict salt pan houses the former Maryburgh Salt Works, on the edge of St Nicholas golf course in Prestwick.

The pan houses, right by the sea front, where dog walkers and families pass on their daily strolls, date back to 1760. They are now quiet and boarded up, but, Marshall explains, they would have been hives of heat and activity. The ground floor would have housed the salt pans, and above would have been the living quarters of the salters.

Records suggest there was a “salt pan hous” in Prestwick as far back as 1480. The two buildings were described, by Christopher Whatley in The Scottish Salt Industry 1570-1850, as "certainly the most complete upstanding remains of the (saltboiling) industry on the west coast”. They are also the most complete to survive in Scotland

Workers would bring buckets of salt water from reservoirs which were cut into the shoreline and bring them into the pan house, emptying the water into large metal basins under which a coal fire would be kept stoked. Although the water would have sat for a while, allowing sediment to settle out, it still contained many impurities and one of the challenges was to get rid of these. The technique favoured in Scotland was to take blood from the local slaughter house, which, tipped into the boiling water of the pans would thicken and produce a scum, on the surface, of impurities that had risen there. On the east coast, the women salt workers were nicknamed the Bloody Witches of Cuffabouts, after the place to the east of Bo’ness, where several of the town’s many salt pans were situated.

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Though the east coast was the heartland of the industry, there were indeed many pan houses in the west. As Whirly describes, “There are so many former salt sites on this coast. Craigie Pans, Allyson's Pans, Ayr Pans, Saltcoats,Anything with pans on the end would have been salt pans. These are small family ones in the west, here, whereas on the east coast they were big, organised big affairs. “

Though Scotland’s last salt pan house, in Prestonpans, was closed in, the industry collapsed long before that. A number of factors caused its decline. One was the agricultural revolution, which mean that cows and sheep no longer had to be slaughtered each autumn simply because there was not enough feed to get them through the winter . There was then no need for salt to preserve the beef and mutton through the harsh cold months. The other was the competition that came from large scale mines in Cheshire, and also Germany and Poland, and the much finer salt that was produced by them.

The Marshalls loved the idea that they were creating a business in a part of the country with a history of salt production. It made it feel right. The family salt import business, Peacocks, for instance was already based on what was called Saltpans Road. “You can’t really make it up,” says Whirly Marshall, “the family were into salt and everything about it but here we are right on the saltpans, right by the sea.”

Peacocks had, for 100 years, been in the business of shipping salt. It had been founded, in n 1874 by John Craig Peacock, who out as a shipping company agent in the heart of Glasgow and it is now one of the largest food salt suppliers worldwide., “The original salt came from all over the place," says Gregorie. "There only are two places in the world that don’t have a natural supply of salt. And one of them is Japan and the other is Scandinavia. You can get it from anywhere.”

This, however, is the first time his family have ventured into producing salt. “For me,” he says, “it was about trying to find a way that was less environmentally hazardous than the old way in which you shoved in loads of coal.”

Once he had visited the graduation towers in Germany, the big question became whether it was possible to do it in Scotland with seawater – in spite of advice that it would not work. The Marshalls had a student test blackthorn to see how much the evaporation would be. They built a small tower. “It’s all very well reading all these articles," says Gregorie, "but no one really knows much about it who is still alive now, so we were trying to work out which angle the wind should be. You can’t move it every time the wind blows. You have to go with the prevailing wind on this coast. You’re always wondering is it going to work even though the theory of it works.

Gregorie got together with a structural engineer and someone who could built the tower, and essentially designed it in collaboration with them. “If we were doing it again," he reflects, "I’d do it differently, but not hugely differently. Some of the things are angled the wrong way.”

In July of 2019 they ran the tower and produced their first round of salt. “It was beautiful," says Whirly. "We called it Blackthorn Gold. It was really exciting coming off. We maybe we dried it off a bit too much. It was a bit crunchy. And then the next batch was quite big.” She points at an array of giant flakes, like small wite mountain peaks laid out on a grey slate. “This batch is from that batch. We call it Sunday salt. In the old days the pans would be shut down for Sundays and the would slowly cool down, which meant that the crystals that formed on Sunday were much better than they were any other day of the week when it was all about making as much salt as possible.”

85 percent of the evaporation is done through the towers. The salt-making process is finished indoors, in a steam-filled pan house that feels like it’s half-spa, half-kitchen. The steel bath in its centre filled with a dark, brownish liquid, which has yet to give off its salt crystals. It looks like a seafood bisque. “We bring it in for the final bit,” says Gregorie. “We heat it up quite hot to start with. A sheet held down at the bottom and then pulled out including calcium sulphate at the top. What happens when crystals start to form they will form the smallest thing possible so even though the micro filters are there it starts to pick up the last bits of chemicals then start to – calcium sulphate will grab onto anything

Were I to come back in another day, he tells me, I would see the crystals forming on the surface, as upside down pyramid, like tiny white boats floating there.. What begins as a small square will grow and grow until it gets so heavy it sinks to the bottom. Gregorie often sounds like an excitable chemistry teacher. “I like the science,” he says. “I’ve been to numerous salt places around the world and you learn bits wherever you go, but until you start doing it yourself and trying to work out – it’s a constant experiment. We’re always changing the temperature, trying out a fan to see if the ripples will affect how quickly it evaporates. There will always be some slight tweak that will make it better”

Their salt has a faint sepia colouring – not always visible unless it is contrasted with something white. Its flavour is subtle and a little sweet. 120g of it will set you back £3.90. At one point the Marshalls tried to make the salt a little whiter, by using filters, yet found that the resulting taste was “awful”. “So we decided to keep it natural. Make something of that fact it was that colour. So now it is a slightly sepia colour which is basically tannins from the bark, from the blackthorn.” Beyond sodium chloride there are other chemicals in here, other salts – calcium, potassium, magnesium as well as sodium, bromides and sulphates as well as chlorides. These affect the flavour, making it sweeter or more bitter. “ The sodium chloride in our salt is about 93 percent,” he says, “the other percentage is these other chemicals. Those are the things that have a noticeable effect on the taste.” Most salts are much higher in sodium than Blackthorn. Maldon sea salt, for instance is around 99 percent sodium, and Saxa table salt, of course, is 100 percent.

There is an ongoing debate over how bad salt, particularly sodium choride, consumed at current levels, is for us. What’s clear is that, whether it's good for us or not, it’s one of the substances we consume in far greater quantities than we ever used to, even in the times when our industry thrived.

Yet, we barely produce it – gourmet companies like Blackthorn Tower being our sole indigenous providers. These salts, and other seasonings like Mara Seaweed, remind us that we have forgotten some of the ways we have used the sea. Yet there are reminders out there, for the most part there only in our street and town names and the remnants of crumbled ruins – in the Maryburgh saltworks or the old windmill at St Monans, Fife.

And the salt itself is still there. It never went away. The salt of sea water is also an endless renewable. And clearly, there are ways of harvesting it. An elegant tower of blackthorn is just one - but there are sure to be others were we to put our mind to it.