How Soap Works


Soap making results from the saponification chemical reaction which occurs when caustic alkali (lye water mixture) – either sodium hydroxide, NaOH (also known as caustic soda) or potassium hydroxide, KOH (also known as potash) – is mixed with animal or vegetable oils or fats. From the reaction between these soap ingredients a new matter is created, SOAP, in which there is no more alkali or oil, but which is made of carboxylate salts (R-CO2-Na), water and glycerin. Glycerin is a by-product of saponification that can be taken away. However it is recommended to keep it in the soap mixture as it brings its moisturising property to soap. To find out the details on how to make soap, follow this link to Soap Making Technique.

Soap is a surface-active product. Carboxylate salts molecules are amphiphilic: they are made of a long chain of atoms, one end of which, negatively polarised, is hydrophilic – attracted by water – while the other end is lipophilic – attracted by fats.

Here is the miracle of soap: the lipophilic end of soap molecule catches fats and pull them from their support, thus cleaning the skin (or any other object to be washed), while the other end is attracted to water. As a result fats caught by the soap molecules are taken away by the rinsing water.

During washing, soap removes fat constituting the hydrolipidic film that covers the skin, protects it and retains its water. Fat is taken away by water along with the dirt contained in it. Therefore washing dries your skin until the hydrolipidic film is restored after several hours. The removal of the protective film by a stripper washing such as the one of commercially produced soaps weakens skin, which, without it protection, is highly exposed to external factors.

A superfatted soap is a soap enriched in fats, such as vegetable oils. The presence of these oils limits the drying up of your skin due to the removal of the natural hydrolipidic film.


Soap Ingredients


You need 3 main ingredients to make soap


Water is a key ingredient in soap making. A highly mineralized water (hard water) would hinder good saponification. Thus it is recommended that you use a low mineralized water such as rain water or distilled water.

Caustic alkali

Sodium hydroxide, or caustic soda, comes as little white tablets or balls. It is a very dangerous product, one must be very cautious when handling it. You may wear rubber gloves up to the elbow, long sleeves, and eye protection glasses while handling it. You could wear thick fabric trousers and a plastic apron as well. It would also be wise to wear rubber boots.

Never forget that caustic soda is corrosive, noxious and dangerous. It must be operated preferably in a well-ventilated area. You must ensure that you do not inhale chemical reaction fumes. The best would be to operate in the open – in a garden or on a balcony.

You must take care to proceed in small quantities, especially if it is to make several kinds of soaps in different colours and various fragrances.

Use preferably glass containers, dedicated to soap making.

In the event of a contact of the skin with soda, you should rinse the affected skin immediately under tap water. In the event of a splashing in the eye, you must rinse abundantly and seek immediate medical advice.

The alkali can also be made from ashes; it is then potassium hydroxide KOH (potash) which is at work.

The major difference between caustic soda and potash is that the first one produces hard soap while the second one produces soft soap.

Oils or fats

Any fat can be used for soap making. The end results will vary according to the fat used. For instance, if you would like a soap that lathers a lot, you should use 20% to 25% of coconut oil. You must be aware, however, that lather does not improve the washing property of the soap at all. It is no more than a psychological element.

Other additives are optional but are of supreme importance for giving your soap its personal touch, its main characteristics. They are what will make your own soap so special: essential oils for specific treatments and fragrances, colouring for the eye, and various other products such as honey, milk, wax, clay, dried herbs, flowers, chopped oatmeal, cornmeal, cocoa powder, … the list is pretty long.

To find out the details on how to make soap, follow this link to Soap Making Technique.