Ancient technique for making salt is back in season after 1,500 years

‘Graduation tower’ made from Douglas fir and blackthorn bushes on the Ayrshire coast harnesses the wind and sea to produce gourmet crystals

A sixth-century technique for making salt has been revived in Scotland to produce premium flakes favoured by Michelin-starred restaurants.
The husband and wife team at Blackthorn Salt in Ayr have built a 30ft tall graduation tower with Douglas fir that was inspired by the traditional Scottish salt-making processes dating back 1,500 years.
Seawater from the west coast of Scotland is filtered and dripped through the tower where 54 wooden taps, in conjunction with adorning blackthorn bushes, take the seawater on a circuitous route to the tank below.
More than 90 per cent of the water is naturally evaporated by the sunlight and brisk coastal winds. The salty brown brine is then sent to a panhouse where a five-day process removes all excess liquid.
Gregorie and Whirly Marshall, owners of Blackthorn Salt, said the response to their gourmet product has been “phenomenal” and it is now used in restaurants including those of Tom Kitchin and Michel Roux Jr.
The company was launched four years ago and has won two Great Taste stars.
Mrs Marshall, 48, is a former architect who has a background in the salt business as his family have been involved with it for generations.
“He is a real foodie and I’m quite eco,” Mrs Marshall said.
“Gregorie came across, when he was working, these amazing salt towers in Germany and Poland and was completely inspired,” she added.
The European towers produce a different type of salt, but the pair were confident the same methodology could be applied to British seawater.
“If you can do it in Germany, you can do it in Scotland,” she said. “We had to work out how to do it and how best to do it.
“[It was a] totally different core ingredient, but we worked out our own way of doing it.” 
The couple, who live in Ayr, Scotland, began working on the project in 2005 and the tower was completed in 2019, with the first salt crystals produced in 2020.
The frame of the tower was created using local Douglas fir wood and it was then stuffed with blackthorn, which is a species of flowering plant in the rose family.
Seawater is pumped into the tower and dribbled through 54 wooden taps and a series of channels, which are checked and adjusted daily depending on the weather, according to the owners.
The water trickles down and with the persistent coastal winds, the droplets partially evaporate and any remaining liquid becomes a more concentrated brine.
Blackthorn Salt has been used by Michelin-starred restaurants across the country, the couple say, with Mrs Marshall calling the response to their product “incredible”.
It has been used in Harrods Grill restaurant, as well as being a favourite of Michel Roux Jr, Mrs Marshall told The Telegraph. Other chefs to have used the salt include Mark Donald, Lorna McNee and Tom Kitchin.
According to the owners of Blackthorn Salt, the first graduation towers were built in the sixth century using straw.
“These towers haven’t been used in 70 years – it’s quite a lost art,” Mrs Marshall said.
The technology matured over the following centuries and today there are several enormous and working examples of the towers in Germany and Poland.
Mr and Mrs Marshall said: “It took years to perfect our unique method of harnessing the wind and sea to ensure we create a better salt, a ‘salt of the world’ as well as ‘for the world’ and one that we are proud of.”
The couple said they were proud to have brought salt back to the west coast of Scotland, where it was once a thriving local industry.
Since launching, the salt has been used on The Great British Bake Off, has been featured on BBC1’s Escape to the Country and has been praised by the TV chef James Martin, as well as used by the Hairy Bikers.