Cold process saponification: what it is, advantages and how it's done
Cold process saponification is a traditional method for making soap from oils or fats and an alkali. Unlike hot process saponification, no external heat is applied during production, and the soap requires a curing period before it is ready.
In this guide, we explain what cold process saponification is, how it is done, how it differs from hot process saponification, and what characteristics the soap obtained through this process has.
What is saponification?
Saponification is the chemical reaction between a fatty substance and an alkali. In the production of solid soaps, sodium hydroxide (NaOH) is usually used; in other formats and formulations, different alkalis may be used. As a result of the reaction, soap and glycerin are formed.
The process can be carried out with different oils and fats and through different manufacturing methods. The two that interest us most here are cold process saponification and hot process saponification.
What is cold process saponification?
In cold process saponification, the oils or fats are mixed with the alkali without resorting to external heating to accelerate the reaction. The mixture begins to react and generates heat on its own during the first phase.
Once poured into molds, the mass is left to rest and then cut. The soap then requires a curing period during which it loses some of its water and the reaction finishes completing itself. The exact time depends on the formulation and the manufacturing process.
It is a slower method than other industrial processes, but it allows for crafting by hand and carefully controlling the raw materials and the formulation.
How is soap made using cold process saponification?
- Selection of oils and fats. The fatty substances are chosen according to the characteristics sought in the soap.
- Preparation of the alkaline solution. The alkali is prepared following a controlled and safe procedure.
- Mixing. The oils and the alkaline solution are combined under the conditions provided by the formulation.
- Molding. The mixture is poured into molds and saponification begins.
- Cutting. When the mass has acquired the appropriate consistency, it is unmolded and cut.
- Curing. The bars rest for several weeks so they lose water and the process finishes stabilizing.
Manufacturing must be carried out with calculated formulations and appropriate safety measures, especially during the handling of the alkali.
Cold process vs. hot process saponification
| Characteristic | Cold process saponification | Hot process saponification |
|---|---|---|
| External heat | Not used to accelerate the reaction | Used to accelerate the process |
| Manufacturing time | Slower | Faster |
| Curing | Requires a subsequent period | The process is accelerated by heat |
| Type of production | Frequent in artisanal soap making | Widely used in industrial processes and certain traditional methods |
Advantages of cold process saponification
Allows working with selected oils
The cold process is especially suitable for artisanal formulations where one wants to control the origin and proportion of the oils used. The choice of raw materials is a fundamental part of the final characteristics of the soap.
Preserves the glycerin formed during the reaction
Saponification produces glycerin. In a cold process soap formulation, the glycerin generated remains integrated in the soap, unless the manufacturer uses a subsequent process that separates it.
Allows for artisanal and controlled production
The absence of prolonged heating makes it easier to work in small batches and closely control ingredients, formulation, texture, and curing times.
A slower process with artisanal identity
Cold process saponification needs time: it is not about making a bar and using it immediately. The curing period is an essential part of the process and is one of the characteristics that differentiate this way of making soap.
Is cold process saponification better than hot process saponification?
There is no universal answer. They are two different manufacturing methods, and the choice depends on the type of soap, the formulation, the manufacturer's process, and the characteristics you want to achieve.
At Home Healthy Home, we have chosen cold process saponification because it fits with our way of making our soaps: careful production, selected raw materials, and an artisanal process.
What oils do we use at Home Healthy Home?
Our soaps are made with organic extra virgin olive oil of Spanish origin as the main raw material. In the different formulas, we incorporate other ingredients according to the use and characteristics of each product.
This philosophy applies both to our laundry soaps and to our personal care products.
What is the difference between a cold-processed soap and a Marseille soap?
The difference is not simply in the name of the soap, but in how it has been manufactured and what formulation has been used. Marseille soap is traditionally associated with a hot process and vegetable oils, while a cold-processed soap is made through a different process and requires curing.
Therefore, to compare two soaps, it is advisable to look at their composition and their manufacturing process, not just their name.
Frequently asked questions about cold process saponification
How long does it take to make a cold-processed soap?
The initial reaction begins during the first few hours, but the bar then needs a curing period that can last several weeks. The specific time depends on the formulation and the manufacturer's method.
Does cold process saponification use soda?
In many solid soaps, sodium hydroxide (NaOH), commonly known as caustic soda, is used. During saponification, it reacts with the oils and forms soap and glycerin. The formulation and process must be correctly calculated and controlled.
Does cold-processed soap contain glycerin?
The saponification reaction generates glycerin. In the cold process, this glycerin normally remains in the bar, unless the manufacturer's subsequent process indicates otherwise.
Why does soap need to cure?
Curing allows the soap to lose some of its water and the process to finish stabilizing. It is an essential phase of traditional manufacturing through cold process saponification.
Cold process saponification at Home Healthy Home
For us, making soap also means respecting the time of the process. We are committed to cold process saponification and carefully selected raw materials to create soaps intended for personal care, the home, and laundry.
Discover our laundry collection and our personal care soaps.
