The Cauldron | The Art of Making of French Soap

You probably clicked on the navigation wondering what The Cauldron was. Traditional and authentic Marseille Soap, and it's predecessor Aleppo Soap, is made in an open air cauldron.

When we think of traditional soap-making, France’s famous Savon de Marseille often comes to mind. But long before Marseille became a hub of soap production, there was Aleppo Soap from Syria. Crafted for over 2,000 years, this olive oil and laurel oil soap is believed to be the world’s first hard soap and the inspiration for soap traditions across the Mediterranean — from Turkey to Provence.

Yes, our Aleppo soap from Tadé and the original soap houses of Marseille Fer a Cheval and La Corvette still make their soap in cauldrons, some of which date from the early 1900's whilst a few have been replaced over the years. This is the soap we import and you buy.

Made exclusively with vegetable oils, free from colour, preservatives and perfume, the oils are mixed and 'baked' in the cauldron, using soda to gradually transform into a soap. Only the master soap-maker has the know-how passed down over several centuries to obtain authentic Marseille soap.

How does this work

It takes around 14 days to make one batch Savon de Marseille through a 5 step process:

The oils and soda are slowly added into a 30ton cauldron under a moderate heat. This is then bought to the boil until it becomes an emulsion. At this point, as soap is insoluble in salt water, sea salt is added in order to drag the excess soda lye to the bottom of the cauldron. The soap will then naturally separate from the water it contains. It is then cooked further, known as saponification, to allow the complete transformation of the vegetable oils into soap. It's then washed! The soap paste is refined by successive washings to remove glycerol, impurities and any unsaponified fatty acids from the cauldron. Fresh water is then added to remove any crystals so that the product is smooth.

Lets look at the ingredients and the terms.

What's in our Pure Olive Savon de Marseille

Ingredient	UK Name	Purpose/Function	Origin
Sodium Olivate	Saponified Olive Oil	Primary cleansing and moisturising agent. Produces a mild, creamy lather.	Plant-based (Olives)
Aqua	Water	Solvent used to dissolve lye and initiate saponification.	Purified Water
Sodium Chloride	Salt	Hardens soap bars; improves texture and longevity.	Mineral-derived
Sodium Hydroxide	Lye	Required for saponification; no active lye remains in final product.	Mineral-derived

 

• What it is: The result of saponifying (reacting) olive oil with Soda/lye (sodium hydroxide).

• Function: A gentle cleansing agent and moisturizer.

• Properties:

  • Rich in oleic acid, which is nourishing for the skin.

  • Produces a mild, low-lather soap that is very gentle and conditioning.
    

  • Glycerin: Naturally created in the soap making process; acts as a skin humectant (moisture-attracting)

 

• What it is: Simply water!

• Function: Solvent that allows lye and oils to mix and react during saponification.

• Note: Most of the water evaporates during the soap curing process, but it's essential in the making of cold- or hot-process soap.

 

• What it is: Common salt.

• Function:

  • Hardens the soap bar.

  • Helps control the texture and consistency.

  • Can also help in separating soap from the glycerin during manufacturing (in industrial soap making).

 

• What it is: A strong alkali used to convert oils/fats into soap through saponification.

• Function: Reacts with oils to produce soap and glycerin.

• Safety note: Although it's caustic in raw form, none remains in the final cured soap if properly formulated—only the resulting soap (e.g., sodium olivate) remains.

• Labelling: Required by law to be listed even though it's used up in the reaction.

The Savon de Marseille from La Corvette also contain Coconut Oil

Sodium Cocoate, known in the UK as Saponified Coconut Oil. It's function is to add cleansing, lather-boosting properties, although none of our soaps will give many bubbles. Another plant derived oil.

To read  more about different and legitimate Savon de Marseille plant oils please read this post we have previously written.

We got distracted, let's go back to the process.

The hot 70ish degree soap paste is then poured into cooling tanks and left to cool and dry. The weather impacts this on a warm summer week it will take longer than a cool winter weekend! Generally around 48hrs but it can take up to two week. 

One dry the soap is cut, moulded and stamped.