'Our salt is the only one in the world to have this unique flavour'
It’s mid-morning at Blackthorn Salt HQ and Gregorie Marshall is having his coffee. There’s a plate of millionaire’s shortbread in the middle of the table and after he reaches for a square, he takes a pinch of Blackthorn Salt from the tiny box he keeps in his pocket and crumbles it over the traybake as naturally as one might season a boiled egg.
He looks surprised when asked why; it’s hard, he says, to explain: “Everyone’s tastebuds are different, but for me it tamps down the sweetness and pulls out something more decadent and moreish – it turns something I like into something I can’t resist.”
He gazes out of the window of the converted Victorian railway carriage where he and his wife, Whirly, run their Ayrshire-based gourmet salt company.
The sea is metres away and beyond it the western coastline of the Isle of Arran, 20 miles across the Firth of Clyde. But it’s not this lovely view on which Gregorie’s adoring eyes are focused. He’s looking instead at the imposing structure in the foreground: a dark tower, 25 metres long with timber walls packed with bundles of spiky branches.
This tower of thorns – technically known as a graduation tower – gave Blackthorn Salt its name and took him nearly 20 years to imagine, design and build.
Only once it was up and running did he know it would produce salt that works like fairy dust on food, its gentle journey from sea to flake creating a balance of minerals that fine-tunes the flavour of everything it touches.
Salt-makers use different methods of evaporating seawater to produce crystals. You can boil it, heat it in a vacuum, use a process called reverse osmosis or air-dry it – in polytunnels if the location isn’t blessed with Mediterranean sun.
Gregorie’s method is to drip it through an eight-metre stack of blackthorn sticks and let the wind and sun condense it into a concentrated brine. “Only someone who is salt-obsessed would go to this length,” says Whirly, as her husband tells the story of how he got the idea.
It was 2005 and he was preparing to join the family business: Peacock Salt in Ayr, founded by his great-great-grandfather and now the UK’s largest importer of salt for road maintenance and industry. While visiting salt mines in Poland, Gregorie came across the 19th-century graduation towers that had been used until the 1960s to evaporate rock brine. As an architect, he was entranced by their form and function.
“Ninety per cent of our process is powered by nature,” he says, explaining that graduation towers work because of blackthorn’s vicious long spikes. “We pump seawater to the top and it trickles through to the bottom, coating the branches and losing moisture as it’s exposed to the air. The spikes increase the surface area of the wood, which means more evaporation.”
How Blackthorn Salt is made
As the future managing director of a salt company that didn’t make salt, Gregorie resolved to build a blackthorn tower and bring sea-salt production back to Ayrshire – the business is based on Saltpans Road, where the last salt pans closed in 1842.
He worked over many years with academics, architects and engineers to finalise his design, which was built in 2018 on a field next to Peacock’s warehouse beside the port of Ayr. Framed in Scottish larch and Douglas fir, it was the first in the UK and the only one in the world producing sea salt commercially.
Fifty-four taps around the top allow Gregorie to adjust the speed at which the sea water is dribbled through the blackthorn sticks, his tweaks dictated by the west coast weather, which affects evaporation. The process is repeated until the liquid has reduced a hundredfold and its salinity (sodium chloride content) increased from 3.5 per cent to 22 per cent.
It is then filtered and piped into the pan house about 20 metres away, where Gregorie and his fellow salter Malky McKinnon tend it carefully in two gently heated baths to tease out soft, flaky crystals.
“The tower gives us a concentrated brine that’s rich in minerals such as calcium, magnesium and potassium,” Whirly says. "We then evaporate that brine slowly enough to retain the minerals that harsher methods such as boiling would remove.”
Michelin chef approval
In the taste tests she hosts for chefs, food producers and stockists in the railway carriage, Whirly grills steak on a woodburning cook stove and slices fruit and salads – radish, watermelon, cucumber – to show off the extraordinary effects of Blackthorn Salt. A ripe tomato turns into a taste bomb when sprinkled with a flake or two: it doesn’t taste of salt so much as a supercharged tomato, its sweetness, sourness and zestiness enhanced and lengthened so it lingers in the mouth memory.
“Calcium brings out sweetness, potassium brings out sourness and magnesium brings out bitterness,” Whirly says. “Our salt has six times more calcium than some other gourmet sea salts, but it’s balanced out by the other minerals.” By contrast, she adds, industrially produced table salt is almost pure sodium chloride hence the one-dimensional sensation she describes as “a sting in the throat”.
There’s another element, unique to Blackthorn Salt, that took the Marshalls by surprise when they harvested their first crystals in 2019. “We noticed they were slightly brown,” says Gregorie, who was alarmed when he realised that tannins from the blackthorn bark had infiltrated the brine. On tasting it, however, they realised these tannins were a magic ingredient. “They add an earthy fifth dimension that brings out a umami flavour in food, making it more resonant,” Whirly says. “It’s a small thing that makes a big difference.”
A small thing that makes a big difference is an apt description of all salt, something we often sprinkle without much thought. Yet a box of Blackthorn Salt, hand-filled and posted out by the very people who take such care over its creation, is an easy way to elevate everyday eating. James Martin, the TV chef and local food champion, has even described it as “one of the most exciting things, in terms of food, in this country”.
Whirly believes it has a personality. “It doesn’t announce itself. It’s not the focus of the meal. It just improves whatever food you’re eating,” she laughs. “I like to think of it as salt without an ego."
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