How is soap made? Let’s be clear. The soap is produced by a chemical reaction , between fatty acids (the main constituents of oils and butters) and a base (usually sodium hydroxide), you get glycerol and a sodium salt. Instead of sodium hydroxide you can use potassium hydroxide, so you will have a soft soap that can be diluted to have a liquid soap, which, however, is more aggressive on the skin than that obtained with soda.
The liquid soaps on the market are very rare, the common liquid soaps are actually synthetic detergents, or a mixture of washing substances of synthetic origin. The liquid soaps can be more or less aggressive than solid soap depending on their composition. The soap molecules and those contained in the synthetic detergents consist of a negatively charged end, similar to water and a long hydrophobic tail, more similar to fatty substances, molecules of this type are called surfactants.
How is soap made and how it is produced industrially
Dirt of a greasy nature cannot be washed with water alone because fats and water do not mix, soap molecules surround the dirt, and can be rinsed away from the water. Producing soap at home is not difficult. Industrially, the soap is produced in large boilers where the mass of fat is heated and slowly the alkaline solution is added.
At the end of the reaction is added sodium chloride to facilitate the separation of the soap from the lye and much of the glycerol that can be resold. In this way we obtain a basic soap, often produced in large quantities and sold to other minor producers who melt it and “customize” it by adding oils, glycerine, perfume …
How is soap made: Ingredients
The label of a soap is usually very simple: first of all there are the starting fats, they can be indicated with their Latin name or as sodium or potassium salt. Hardly a soap is made with a single oil, you need at least two to have a product with the right consistency, not slimy and that makes a nice foam. The oils we find most commonly are palm oil and coconut oil. The first ,it makes the soaps very hard and therefore they are consumed more slowly, the second gives a nice foam.
Pork fat produced from slaughterhouse waste (lard/sodium ecc…), is particularly present in laundry soaps. Depending on your personal sensitivity, you may decide to exclude products with pork fat (therefore not VEGAN) and those containing palm oil. Every year, many areas are deforested to make room for the palm plantations from which this oil is obtained with serious damage to biodiversity, not buying products that contain palm oil is not easy, is also contained in many food products under the words “vegetable fats”.
Another oil that can be present in soaps is olive oil, soaps made with olive oil are hard, but delicate, it is usually combined with coconut oil to get a better foam. After the oils on the label there is always sodium (potassium) hydroxide, it is not indicated if instead of the names of the oils there are those of their salts.
How is soap made: additional ingredients
Oils or butters (karitè, almonds…), these are not saponified and they are used to sweeten the soap.
Glycerin is a by-product of saponification, industrially it is often separated from the soap to be used in the pharmaceutical or explosives industry. Producers who do not manufacture soap themselves, but buy it raw often add it again to refine the product.
Perfumes, indicated with the generic “parfum”, are generally of synthetic nature, but can also be made by perfumed essential oils. Be careful, because often the essential oils being strongly concentrated may contain allergens. It is mandatory to indicate on the label the substances recognized as allergenic if present at a concentration more than 0.01%, both if of natural origin, and if of synthetic.