On the west coast of Scotland stands a wooden structure that could have been conjured from a fairytale.

Almost 30 ft tall and more than 100 ft in length, it is an imposing tower of Scottish timber filled with thousands of blackthorn branches. From each branch and thorn drips seawater, which will in time become premium sea salt destined for the shelves of farm shops and kitchens of high-end restaurants. 

The Blackthorn Salt graduation tower is the result of 15 years of research, experimentation and commitment by Gregorie Marshall, MD of Peacock Salt.

Marshall is the great-great grandson of founder JC Peacock, who started the company in 1874 as a shipping business. Today, Peacock claims to be the largest distributor of salt products in the UK, supplying it for uses including de-icing, cleaning, food and cosmetics.

“I’ve always wanted to make our own salt,” says Marshall, who trained and worked as an architect before joining the family business. “My mother was a cordon bleu cook and, I suppose, salt, the cooking and the architecture sort of combined together to produce the Blackthorn Salt.”

Marshall hasn’t hurried the development of Blackthorn, as he wanted to ensure Peacock got it right. “Being a family business and not being owned by venture capitalists, we don’t need a result tomorrow.” 


Research took him across the globe to look at the wide variety of production methods. “In Japan, there are more than 200 different types of salt, and they have many ways of doing it to produce a different taste or flavour,” he says.

Scotland itself has a long history of salt production, peaking in the 18th century, when producers would heat huge pans of saltwater over coal to evaporate the water.

“That used a huge amount of energy and, having looked at all the different methods I was keen to try and get something that is sustainable and environmentally friendly,” says Marshall.

The Blackthorn production method was inspired by similar graduation towers that had been used in Poland and Germany.

“We are trying to expose as much of the water to the air as possible, so we trickle it down through the branches to expand the surface area,” he explains. “At the final stage, we do have to heat up the pan. We evaporate just over 90% of the water naturally and only the last section needs any energy.”

It sounds so simple, but the devil is in the detail. Marshall worked with Strathclyde University to determine the best angle for the tower to maximise use of wind, the best angle for the branches, and the best angle for dripping water.

“We ended up with three or four figures, but those three or four figures are very important to the whole design of it,” he says.

with thorns 6

Construction of the tower took place in 2018, with local craftsmen and joiners using douglas fir and larch from Dumfries and Galloway. It was a big job. Even bigger, and at times painful, was the task of filling the tower with the spiky blackthorn branches from Ayrshire.

Blackthorn was chosen because it is a hard wood. The business plans to plant a field to supply the future needs of the tower.

In spring 2019, with the tower complete, seawater started to be dripped through the blackthorn from a series of taps.

“We trickle it down the tower and, as it goes down, we’re evaporating the water,” says Marshall. “Sometimes we can get quite good evaporation. Other times, it can just stay at zero, because the humidity is too high or it’s raining.”

It isn’t possible to put a roof over the structure to keep off the rain because it would impact airflow and prevent evaporation.

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The seawater is circulated back round the tower until it reaches a concentration of about 22% salt. It is then pumped to the pan house, where it is heated for about five days to form salt crystals.

The aim is to produce a crystal that is easy for the user to handle and crunch in their hands.

“It took us a long time to get to what we wanted by adjusting temperatures and adjusting timings,” says Marshall. “With the cycle being five days it could be frustrating, but what we’ve got is exactly what we were looking for.”  

Process adjustments were required in the early days, as the first salt produced was quite a strong amber colour due to high levels of tannin, he adds. 

Blackthorn Salt Aug 2020 (59)

“We started looking at different filters and we got it looking a lot whiter but it then started to taste less good because we were taking out all the elements such as potassium, magnesium and calcium.”

Blackthorn Salt is now is about 94% sodium chloride, compared with around 99% in table salt.

“It’s ultimately that 6% of different elements that has a huge effect on the flavour,” says Marshall. “It makes it a lot sweeter and allows what you’re tasting to come through more. It enhances the flavour rather than taking it over.”

When talking to buyers and chefs, he demonstrates the salt’s difference by slicing a tomato and putting regular salt on one half and Blackthorn on the other. “You will absolutely notice a difference, without a shadow of a doubt. Ours is sort of mellow, and it allows the sweetness and the tastes and flavours to sort of roll over your tongue.”

In March 2020, after 15 years of preparation, Blackthorn Salt was ready to launch via a live event for chefs. Then the UK entered lockdown.

The response was ‘Pass the salt’, a campaign in which the chefs were sent a box of salt and vouchers for more to give to friends. Blackthorn also made boxes of salt available free online, with consumers paying only postage and the brand donating the cost of each order to local charities. Salt was also given to restaurants that were supplying food to NHS workers.

“It just felt wrong to go out and sell stuff at a time like that,” says Marshall.

Blackthorn Salt Aug 2020 (74)

As pandemic restrictions have eased, distribution has begun building, and 10 Michelin-starred restaurants now use Blackthorn. The salt is also listed with two retail distributors and is gaining shelf space in farm shops and delis.

“People are thinking more about locally produced and sustainably produced and those things are key to what we are doing,” Marshall says.

Blackthorn retails at a premium price of £6.40 for a 240g box, but once people try the salt and realise how much better it is, it is an easy sell, he adds. “That box is going to last you six months, and many people will spend £6 on a bottle of wine and finish it in a night,” he says, adding that educating consumers is key.

“People say ‘salt is just salt’. But that is like saying wine is just wine.”



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