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close this bookHow to Make? An Improved Soap .. Not just for more Foam (GTZ, 1993, 71 p.)
close this folderC. Saponification of simple fats
View the documentC.I. Peanut oil
View the documentC.II. Copra oil
View the documentC.III. Cotton oil
View the documentC.IV. Shea butter
View the documentC.V. Palm oil
View the documentC.VI. Palmkernel oil
View the documentC.VII. Tallows (cow and mutton)
View the documentC.VIII. Fat (pork)
View the documentC.IX. Neem oil
View the documentC.X. Pourghere oil
View the documentC.XI. Castor oil
View the documentC.XII. Sesame oil

C.III. Cotton oil

It is extracted from cotton seeds (Gossypum sp.).

The physical and chemical characteristics are the following:

Density at 15 °C:

0,92 - 0,93

Solidification point:

0 to 4 °C

Iodine number:

100 - 117

Saponification value:

190 - 198

INS Factor:

73 - 98

Intake in insaponifiable:

0,50 - 1,50 %

Intake of caustic soda solution indicated for saponification (refined oil):

12 to 15°Be

Caustic soda soap is yellow colored, soft and less soluble in water. It has a good washing power and produced an average stable foam. It's effect on the skin is rather smooth. Not well adapted to conservation, it shows a great tendency to formation of stains and to growing rancid during storage.



The raw cotton oil presents a dark brown color due mainly to its intake in gossypol (a toxic polyphenolic substance). Moreover it produces a specific scent and should consequently under go a refining before saponification if you want to achieve a product with acceptable quality.

As simple method of purification you can use the refining by treating with a light alkaline solution. The alkaline contained in this solution forms with the free fatty acids of oil small flocks of soap, which adsorb and eliminate from the oil odorous and colorours substances as well as impurities. These flocks are then eliminated by settling.

The process consists in:

- Weighing the quantity of raw oil and heating it at about 50 °C;
- Adding an alkaline solution of 20 °Be (about 10% of the raw oil weight) by stirring during 30 minutes;
- Leave it become cold (flocks will then be deposited) and settle the refined oil.


To achieve this the semi-hot process should be used.

100 Kg of purified cotton oil;
34,4 Kg of caustic soda solution at 12 °Be;
62,75 Kg of caustic soda solution at 24 °Be;
5 Kg of kaolin.


How to carry out the operation

- Weigh the necessary quantity of purified oil;
- Heat the oil in the boiler at a temperature of 55 - 60 °C;
- Stop the heating;
- Add the necessary quantity of alkaline solution by stirring (in case you use caustic soda take a solution at 12 °Be)
- Go-on stirring during a few minutes until the appearance of an indication that the temperature has really gone up;
- Stir from time to time and let the temperature decrease to about 60°C, and then check the quality of the soap;
- Add and incorporate the auxiliaries;
- Pour the hot mass into moulds and leave it to become cold;
- Take the hardened blocks out of the moulds and cut them into bars and pieces.