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Saponification à froid.

All you need to know about cold process saponification.

Soap is the product of a chemical reaction between a fatty substance and a strong base: cold saponification. This soap-making technique allows for the preservation of the properties of the ingredients used as much as possible. We provide more details on this process and its benefits.


What is cold process saponification?

The cold saponification is a traditional method used to make soap. It involves the transformation of fatty substances (in our case, vegetable oils and butters) into soap under the action of a strong base (lye for the creation of solid soaps or potash for solid soaps). In addition to soap, this chemical reaction also produces vegetable glycerin, a fatty substance naturally present:

Fatty substance + Strong base (sodium hydroxide or potassium hydroxide) = Glycerine + Solid or liquid soap.

This traditional soap-making method is a slow chemical reaction, which takes place at room temperature (between 27° and 45°C), followed by a lengthy and natural drying process. It is the combination of the fatty acids from the melted oils and fats with lye (sodium hydroxide) that generates heat and thus facilitates the saponification process. This stage takes approximately 48 hours. This is the necessary time frame for the chemical reaction to occur on its own, naturally.

Furthermore, this transformation is referred to as a "complete reaction", meaning it will cease once one of the reactants used is exhausted (oils or lye/potash). Generally, for a cold-process soap to be used, there should be no trace of lye left. The reaction will therefore stop when all the lye has been consumed and there is an excess of oils: this ensures that there is no lye left in the final soap.

The soap thus obtained is then referred to as "superfatted" with this surplus of non-saponified oil. This superfatting can be explained in two ways: either by reducing the lye , which involves using less of it, or by adding oil or vegetable butter at the end of the preparation. At Typology, we have opted for the second method: thus the indication "8% superfatted" means that the soap is composed of 8% of fatty substances not transformed into soap and glycerine. This provides greater softness, and nourishing and softening properties to the soap.

The cold saponification process: the steps of implementation.

  1. Firstly, butters and solid oils are melted and then allowed to cool to room temperature. The lye, diluted in a liquid (water or hydrosol), is then added and mixed into the still liquid preparation, at room temperature. Upon contact with the lye, the mixture begins to thicken and a soap paste forms: this is what is referred to as the "trace";

  2. It is at this point that it becomes possible toadd other ingredients to the mixture (essential oils, exfoliants, colourants, antioxidants, clays, milks, etc...) and even to add melted oils or butters to achieve a "superfatted" soap;

  3. The mixture is then placed into a mould before it hardens and left to rest for 24 to 48 hours so that the reaction can occur on its own, naturally, over time. Once the reaction has completed, the soaps are ready to be unmoulded and cut;

  4. After unmoulding, the soaps then need to undergo a drying period (or "curing" time) of a minimum of 4 weeks, allowing the water to evaporate and thus prolong their lifespan. In addition to letting them harden, this also allows time for the saponification process to fully complete and for the soaps to stabilise their pH level.

What is the difference with the hot saponification process?

Unlike cold saponification, hot saponification involves the use of heat: the mixture (fat + lye/potash) is heated to extremely high temperatures (around 120°C) for 10 days, which accelerates the chemical process. However, this results in the loss of a significant portion of the properties of the ingredients used in soap production. Moreover, the lye is not entirely converted into soap and to completely eliminate it, one must wash the soap with large quantities of water at the end of the manufacturing process. Additionally, this step extracts almost all of the glycerine.

The benefits of cold process soaps.

There are several advantages to cold saponification. Firstly, it allows to preserve the entirety of the naturally produced glycerine, thus giving the soap a moisturising power. Moreover, some ingredients do not react with the lye and are therefore preserved, such as tocopherols (vitamin E), phytosterols, terpenes or even squalene: these are the unsaponifiables. They have antioxidant, nourishing and protective properties. A cold saponified soap will therefore contain an unsaponifiable portion of the oils used and allows to benefit from their advantages. Finally, thanks to the surplus of fatty matter, the skin retains its hydrolipidic film after the shower and is therefore not dried out. At Typology, we offer you soaps exclusively cold saponified allowing to preserve the properties of the used vegetable oils and butters.


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