Here is the explanation of the production by La Savonnerie

The “Le Serail” soap factory is the last artisanal and traditional soap factory in Marseille based in the Phocaean city.

In the 1900s, Marseille, a large city in Provence, saw its soap factories - around a hundred at the time - closed one after the other due to the massive arrival of detergents. A man, returning from deportation to Germany, Vincent BOETTO, made the bet of creating Savonnerie le Sérail in 1949, in order to perpetuate the know-how and tradition of genuine Marseille soap. He then took over a farm located inside the city, and installed the equipment necessary for the manufacture of the traditional Marseille soap cube, including the cauldrons in which the soap paste is made. Today, it is his son, Daniel, proud of this heritage, who took over the reins of the soap factory in 2009 and who continues the know-how left by his father. Thus, all the material is period, and has been preserved as well as all the steps necessary for the manufacture of traditional Marseille soap, which has also enabled it to obtain the “Living Heritage Company” label. awarded by the CCI of Marseille.

I - The manufacturing process of authentic Marseille soap at Savonnerie Le Sérail

Authentic Marseille soap is made in a cauldron, using a specific saponification process called the "Marseillais process", comprising five steps:


1st step :

mashing, or chemical reaction of saponification

The oils of vegetable origin are heated in a large cauldron. Under the action of soda and heat, they gradually turn into soap.

2nd step: release

Since the soap is insoluble in salt water, this operation involves adding sea salt to drag the excess lye to the bottom of the cauldron, with the remaining soap on top.

3rd step: cooking

This operation characterizes the saponification and allows the complete transformation of vegetable oils into soap.

4th step: washing

The soap paste is refined by washes, removing glycerol, impurities and unsaponified fatty acids.

5th step: liquidation

A final wash with clean water brings the soap to its final state: a smooth and pure soap which has made the reputation of the Marseilles process. These different operations take about a week. Each cauldron can hold eight tons of soap paste.

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Then comes the casting.

The soap is poured hot (70 °) into basins called "mise", where it will cool and solidify for about three days.

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The cutting

The soap slab is then cut into blocks of 40 to 50 kg before being re-cut into units of 1000g - 600g - 400g - 300g. Everything is done manually on vintage machines.

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Drying

The soap cubes are then placed on shelves, where they will air dry for a week to two weeks so that the water they contain can evaporate.

 

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Stamping

All of the production is artisanal and the cubes will be stamped one by one in soap presses with vintage tulip molds. The soap is then marked on all six sides.

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II - Multiple virtues

Nowadays, the return of ecological and economic values ​​make consumers (re) discover the virtues of Marseille soap, which is both good for the skin and good for the environment. Hypoallergenic Biodegradable in less than 28 days Recommended by dermatologists to combat dry skin Economical in use

source  : site officiel Le SERAIL