You can't mistake an authentic bar of Marseille soap. Olive green or creamy white, it's a large, perfect cube, embossed on all six faces, with no added perfume or fancy packaging. Here is our essential guide to one of the city's most famous products.
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HOW GENUINE SAVON DE MARSEILLE IS MANUFACTURED
Paradoxically, a soap labelled "Savon de Marseille" doesn't necessarily come from Marseille. Many brands flagging themselves in this way are actually cheap imitations produced many thousands of miles away using an entirely different process.
Real Marseille soap is made exclusively from natural olive, palm and - sometimes - other vegetable oils without any colouring agents or artificial additives.
Its colour is green if made with olive oil and cream if made with palm oil. It must contain a minimum of 72% oil, and the percentage must be stamped on one of the faces of each bar of soap. Click here to read our full guide to the olive oils of Provence.
It takes around two weeks to process savon de Marseille and a month before the soap is shop-ready. First, oil and soda are mixed in a large cauldron and cooked for eight to ten days at a temperature of 120 degrees Celsius (248 degrees Fahrenheit). The long boiling process means that the finished soap bars can be kept for years without turning rancid.
The mixture is washed several times in salt water in order to eliminate the soda, tipped into huge moulds and left to set for two days at a temperature of 50-60 degrees Celsius (120-140 degrees Fahrenheit).
Then it's cut into cube-shaped blocks and set out in a well-aired place to dry completely, turned from time to time to expose each of the six sides to the air. A typical bar of Marseille soap weighs a hefty 600 grams / 1 lb 5 oz.
Enthusiasts claim that the combination of Marseille's fierce sun, Mistral wind and salty sea air contribute to its soap's distinctive character. The white bloom on the finished soap is a faint residue of sea salt.
The final stage is for the soap to be hand-stamped on all six faces with various information.
This should include the manufacturer's name, the weight, the percentage of oil and, of course, the legend Savon de Marseille (the soap can also be sold in large bars or as flakes). Pictured: traditional stamps from the Marius Fabre soap factory.
A THUMBNAIL HISTORY
Pliny the Elder's Natural History mentions an early form of soap made of a toxic-sounding mix of goat fat and beech ash, invented by the Gauls to condition their hair and colour it red.
Marseille soap was first produced as early as the 12th century and had more appetising ingredients: olive oil and soda derived from the ashes of sea-asparagus and other marine plants from the Camargue.
Factories quickly began to multiply to the point where rivals began using cheaper ingredients to keep costs down.
To improve standards, Louis XIV - the Sun King himself - issued an edict on 5 October 1688 laying down ground rules for the savon de Marseille. No butter or animal fats could be used in the soap mix, only pure olive oil. And restrictions were placed on the manufacturing season.
It had to start after 1 May in order to give the oil time to mature after the annual mid-winter pressing, and must cease during June, July and August, when the weather was too hot for the soap to set properly.
Many of Marseille's soap factories were clustered along the south side of the Old Port and were organised on three levels: fuel and boilers in the basement, giant cauldrons on the ground floor and racks for drying the soap on the upper levels.
Pictured: the cauldron room in a 19th century soap factory in Marseille, from Les merveilles de l'industrie ou, Description des principales industries modernes by Louis Figuier, pub. Furne, Jouvet, Paris, 1873-1877.
Business boomed and Marseille soap was exported worldwide. By the early 20th century it had become the city's main industry. In 1900, 60% of the population was involved in soap-making in some capacity and records from 1908 state that the city then had 81 factories producing 140,000 tonnes (308 million pounds) of soap a year.
After going through various mutations in the course of its history, the manufacturing process and recipe had become roughly what they are today.
Savon de Marseille was a versatile, all-purpose product, used by housewives for domestic cleaning, washing dishes and clothes and as a shampoo, conventional soap and even toothpaste.
Pictured: a vintage publicity poster for Rationnel, one of the many brands of soap being produced in Marseille during this period.
But Marseille's soap industry was hit hard by the Great Depression and two World Wars. And the arrival of washing machines, which required soap flakes, was another blow.
Washing powder was invented in 1906 by a Marseille chemist, Jules Ronchetti, who gave it the brand name of Persil, taken from two of its original ingredients, sodium perborate and silicate (his logo was a bunch of parsley, persil in French).
Unsuccessful in capitalising his invention, Ronchetti was to see it taken over by Lever Brothers, who made a fortune from it.
In the late 20th century the market for soap fragmented still further. Consumers developed a taste for perfumed soaps in fancy packaging, shower gels and specialist washing powders.
The humble bar of everyday, all-purpose savon de Marseille fell from favour. Today there is just a handful of factories in the immediate area.
But the mood is swinging back, and the purity and simplicity of savon de Marseille are increasingly recognised as both ecological and economical.
It's well-suited for anyone with skin allergies as well as for washing silk and other delicate fabrics. A folk remedy even claims that placing a bar of Marseille soap at the foot of your bed helps alleviate rheumatic pain.
Many soaps labelled "savon de Marseille" have actually been manufactured very far away indeed from Provence - in Turkey or the Far East.
Their brand names might sound traditional but the trademark "Savon de Marseille" belongs to the Henkel group in Germany. Le petit Marseillais, a popular line of bath gels and shampoos, comes from a subsidiary of the American company Johnson and Johnson.
In December 2013, after much lobbying, it was finally decided to award savon de Marseille an IGP (Indication géographique protegée), or protected label.
When fully implemented, this measure will authorise only soap manufactured within the Bouches du Rhône départment using the traditional process to be sold as savon de Marseille.
Of course, as currently happens with champagne, the cheap copycats will be able legally to market their soap with such misleading slogans as "savon à la Marseillaise" or "méthode marseillaise" so it will still be a case of buyer beware.
To raise awareness during the very long campaign for the IGP label, a monster cube of Marseille soap, weighing 80 metric tonnes / 40,000 lbs was manufactured and "inaugurated" in April 2013.
Conceived by the street arts association Générik Vapeur, the three-metre / ten-foot high cube, pictured, sat in front of Marseille's J1 Hangar gallery and was named the Clepsydre, after the ancient Egyptian water clock.
Placed above it, a giant tap dripped water to melt the cube gradually away, symbolising the passing of time. Visitors also chipped at the soap, carving their initials on it or cutting pieces off to use or keep as souvenirs. As planned, at the end of September 2013 what remained of this unusual "pop-up" artwork was taken away.
Where to buy savon de Marseille: Marseille soap is easy to find in the many shops on and around the city's Old Port. Online, you can buy soap by Marius Fabre here. Pictured: traditional santons (terracotta Christmas crib figures) depicting a cluster of washerwomen.
Soap factories (savonneries) in Marseille and the surrounding region, some of which offer factory visits:
In central Marseille: La Grande Savonnerie, 36 Grand rue, 13002 Marseille. Website for La Grande Savonnerie
Also in central Marseille: La Savonnerie Marseillaise de la Licorne, 34 cours Julien, 13006 Marseille. Website for La Savonnierie de la Licorne
In the northern suburbs of Marseille: La Savonnerie Le Fer à Cheval, 66 chemin de Sainte Marthe, 13014 Marseille. Tel: (+33) 4 91 10 30 80 Website for La Savonnerie Le Fer à Cheval
La Savonnerie Le Sérail, 50 boulevard Anatole de la Forge, 13014 Marseille. Tel: (+33) 4 91 98 28 25 Website for La Savonnerie Le Sérail
La Savonnerie du Midi, 72 rue Augustin Roux, 13016 Marseille.
In Salon de Provence: La Savonnerie Marius Fabre, 148 avenue Paul Bourret, 13300 Salon de Provence. Tel: (+33) 4 90 53 24 77 Website for La Savonnerie Marius Fabre
In Salon de Provence: Rampal Latour, 71 rue Félix Pyat, 13300 Salon de Provence. Tel: (33) 4 90 56 07 28 Website for La Savonnerie Rampal Latour