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close this bookHow to Make? An Improved Soap .. Not just for more Foam (GTZ, 1993, 71 p.)
close this folderA. Basic elements for making improved soap
View the documentA.I. Raw materials
View the documentA.II. Technology of improved soaps making

A.II. Technology of improved soaps making

Soap fabrication from neutral fat (triglycerol) and alkali (for instance caustic soda, NaOH) is achieved according to the following reaction:










caustic soda





According to the conducting temperature of the saponification reaction, we distinguish three (3) different methods of soap-making: the saponification at cold temperature, the semi-hot saponification process and the hot process.

A.II.1. Cold saponification process

It is a simple process which requires less time and energy. Moreover the produced soap contains glycerine. This has a good effect on skin and can contribute to a better conservation of soaps during storage (prevention from dehydration). This soaps are well soluble and produce a lot of foam.

The main disadvantages of this method are:

- All fats are not usable for saponification according to that process, particularly some proportion of copra butter and/or palmist oil should be incorporated into the fats mixture;
- The soap produced contains all the impurities of the reaction mixtures;
- A surplus of free alkaline is necessary to prevent the rancidity.

Operating method:

The (mixture of) fat is heated in the boiler up to 40°C. Then You add the necessary alkaline solution tin small portions at the beginning), by stirring well in the same direction. By using caustic soda, the appropriate solution must have a concentration of 20 to 35% of NaOH (or about 26 to 40 °Be. By correct operating, the reaction produces enough heat to ensure a complete saponification.

The auxiliaries (additives, color, scent) are incorporated when the reaction has really started (the mixture then shows a consistency which looks like that of honey). The warm mass is then poured into big moulds where the complete saponification reaction is achieved.

A.II.2. Semi-hot process

This method of saponification is also easily to implement if you practice the following way:

- Heat fat (or mixture of fat) at about 55 - 70 °C;

- Add (slowly and in small portions at the beginning) the alkaline solution necessary to saponification by stirring (the reaction produces heat and the temperature of the mixture can increase up to 90°C)

- Leave the mass become cold to 60°C and mix in the auxiliaries;

- Pour the soap in containers (for 24 to 36 hours) and leave it until it becomes cold and hard.

The above mentioned cold and semi-hot processes are quite well indicated for improved soap-making at home and small-scale levels considering their easy implementation and the quality of the products they can generate

A.II.3. Hot or full boiling process

This method of saponification is mainly used for production of hard sodium soaps.

The implementation of operations is identical to that of semi-hot process until the real starting of soap formation (increased viscosity of the reaction medium). From this stage, you add by portions the remainder of the alkaline solution by stirring when being heated. After adding the calculated alkaline, you heat the mass up to ebullition during a few hours.

At the end of this operation practice, the graining out consisting in adding salted water or humid salt, must be carry out. The initial mass divides then into 2 phases: an inferior stage composed of salted water, glycerol and soluble impurities present in the mixture and a superior stage composed by the soap (insoluble in salted water).

The resulted soap undergoes again some special operations (cocking in a strong bleach, liquidation etc.) before being poured in moulds for hardening.

This process, when correctly executed can produce a soap of semiindustrial quality. According to its complexity and the high cost of investments for purchase of adequate equipments, this process can be recommended only for production of semi-industrial soap.

The above described process enable production of laundry and simple toilet soaps. To produce special soaps (high class toilet soap, transparent soaps, medical soaps, shaving soap etc.) the application of other soap making processes is necessary.

A.II.4 Control of saponification

To follow-up the execution of saponification and to control the quality of the soap produced, you can practice two simple methods:

- A sample of well soap should melt in water without turning it muddy;
- The presence of small drops of fat bodies indicates a shortage in alkaline, thus incomplete saponification;
- A well made improved soap shall present a light spicy taste due to the light surplus of alkaline necessary for a good preservation for rancidity

For the consumer a good soap should have the following qualities:

- Have a clear color, fast white;
- Be hard on touch;
- Produce quickly abundant and stable foam;
- Have a soft and good effect on the skin;
- Be able to conserve during a long period without loosing the above mentioned qualities.

Soaps produced from simple fats scarcely have all these qualities.

The saponification of fat mixtures gives the operator the advantage to be able to influence the qualities of the final product by choosing fats with complementary properties as component.

For this reason, the best soaps are produced in practice by saponification of fat mixtures different origins. So, if you want to produce a hard consistency soap, the INS Factor of the mixture should have a minimum value of around 110. You therefore can choose fat which soaps have different qualities as concerning foaming, cleaning property, action or effect on the skin.

The limitating element to the extent of such compositions is the availability of the appropriate fat on a considered geographic area. The availability of the fat according to their source in the 3 main ecological zones which characterize the developing countries is the following:

Equatorial zone

Humid tropical zone

Semi arid tropical zone




fat (pork)





tallow (mutton, cow)


fat (pork)



castor plant

In chapters C to G the technical details about preparation of improved soaps at family and small-scale level (cold or semi-hot process) and based on locally available fats are explained.