It took an American in southwest France to revive an ancient blue dye that once brought riches to the region and was so prized it was lauded in Chaucer's poetry and used for uniforms in Napoleon's army.
"We brought this 'Pastel' back into fashion," said a proud Denise Simeon-Lambert, using the region's old Occitan-language word for her tint that has wooed mega-designers like Dior and Chanel.
The US-born Simeon-Lambert is one of two business owners aiming to restore international acclaim to this forgotten "blue gold," as it was dubbed for the wealth it once brought to local dyemakers. Today they draw customers as far away as Asia.
Yet it was by accident that the energetic 60-year-old, who grew up in France and married a Belgian, stumbled upon the concoction made from a plant also prized for its curative values.
The dye, from the Isatis tinctoria whose inauspicious English name is woad, fell out of general use in the 17th century when new shipping routes brought in the more concentrated and easier to produce indigo from India. This in turn was pushed aside in the last century by synthetic tints.
In 1994, Simeon-Lambert and her husband left Belgium and moved into a 15th-century tannery in Lectoure, population 3,700, in the Gers region.
Intrigued by the luminous shade of their new home's shutters, she set about researching the blue in what "became a veritable passion" -- and quickly a family business.
Originally used in Greece, Turkey and Egypt, woad "has always fascinated," said Simeon-Lambert. "The plant is green, the flowers are yellow and they produce a blue colouring."
Now a widow, she runs her firm, Bleu de Lectoure, with her son and daughter and has boosted production to 600 kilogrammes (1,300 pounds) of dye each year but "is aiming for 2.5 tonnes".
With the drive for environmentally safe products, there is "a strong demand from haute couture and the (textile) industry since this dye is non-polluting and doesn't run," she said.
They have also developed a line of art supplies, beauty products and textiles, and plan to open a second factory in the United States.
- Fashion and beauty -
French businesswoman Carole Garcia, who worked in the pharmacology industry, has focussed on "reviving the medicinal side of this plant, developing cosmetic products".
Pastel has also been known "since the Middle Ages for its therapeutic value," she said, so in 2003 she left her job to create her Toulouse-based Graine de Pastel firm.
Unlike the dye, which uses the woad's leaves, "we use the seeds to extract oil that is rich in nutrition," she said.
Her products have fed a fast-growing niche market for organic cosmetics in France and abroad.
"We make 25 percent of our turnover from export, notably to Asia," said Garcia, who now has three stores in France and plans to open eight more in 2016.
Between 1450 and 1600, "pasteliers," as they were called, in the industry's golden triangle from Toulouse to Albi to Carcassonne, ran a thriving business until imported indigo killed their trade.
Ironically, there remains little trace of the early extraction process when woad leaves were ground and turned into "cocagnes", balls of plant paste allowed to ferment then dry.
Instead, Simeon-Lambert and her husband patiently tested other methods until they came up with one "similar to those from the 19th century to dye the uniforms of Napoleon's soldiers -- the last time pastel was brought, briefly, back to life."
Once they are cut from the plant, the pastel leaves -- known as rosettes -- are soaked in water for 24 hours to release their pigmentation agent.
The resulting colourless liquid is then dumped into an oxidation tub, where contact with the air modifies the structure of the colouring agent until it forms solid blue crystals. This insoluble "blue gold" must then be further processed before final use.
"It's a capricious blue, but it has extraordinary qualities. It ennobles all the fibres in any cloth, and is indelible," says Simeon-Lambert.
After a long preparation process that follows, the dye is finally ready for use.
"Look at the magic of this alchemy!" cries Simeon-Lambert as an employee removes a towel from a colouring vat. The contact with the air caused the cloth to change over the space of several seconds from yellow to green before assuming its definitive blue hue.