Acid in Soap

The art of soap making dates back several centuries. Ancient people supposedly used soap-like materials for cleaning purpose. Soap is a combination of oils or fatty acids and alkali. The resultant reaction produces a compound called glycerin as well as the sodium salt of the fatty acid used. Different types of combination of fatty acids and alkali are responsible for the various properties of soap. Lather, cleansing ability and the mode of reaction of the soap are all dependent upon the particular acid in soap. If you are interested in soap making, you may go through the list of some commonly used fatty acids in soap.

Fatty Acids in Soap

As mentioned earlier, the fatty acid content in your ingredients will determine the eventual characteristics of your finished product, i.e. soap. Let us look at some of the fatty acids involved in making soap and the characteristics each of them lend to the soap.

Stearic Acid
Stearic acid is the most important ingredient for making soap bars. It renders hardness to the soap mixture, which facilitates the molding of soap. It also gives a creamy texture to the soap lather. Stearic acid in soap also has strong cleansing properties. Overusing stearic acid in bath soaps results in dryness of skin.

Lauric Acid
Lauric acid is also responsible for the hardness of soap. It produces rich, fluffy lather. Lauric acid has immense cleaning abilities which help to get rid of oil, grease etc. If used in large amounts in bath soaps, lauric acid can strip the skin of its moisture and natural oils. Ingredients like coconut oil, Babassu oil or palm oil are rich sources of lauric acid.

Oleic Acid
Oleic acid is responsible for the slippery, soapy feel of the soap bar. Oleic acid is a good skin conditioner which is used in bath soaps for its moisturizing properties. However, oleic acid does not produce a rich lather.

Linoleic Acid
Linoleic acid also has good moisturizing properties. The silky, smooth feeling that you experience after having a bath with certain soaps is due to the linoleic acid present in them. Linoleic acid has the property to turn rancid more quickly than other acids. This often leads to formation of orange spots on the soap bar. Thus, linoleic acid is to be avoided if you want your soap bar to last long. Linolenic acid is also known for its moisturizing and nourishing properties. It is used for very mild soap formulations.

Linolenic Acid
Linolenic acid is also known for its moisturizing and nourishing properties. It is used for very mild soap formulations

Ricinoleic Acid
Ricinoleic acid is mainly used in soap making for its ability to produce very dense, rich lather. It can produce foamy as well as creamy, stable lather. Even small amount of ricinoleic acid is capable of producing thick lather.

Palmitic Acid
The properties of palmitic acid are somewhat similar to those of stearic acid. Thus, palmitic acid and stearic acid are interchangeable in soap formulations.

Myristic Acid
Myristic acid has all the properties of making a good soap. It has powerful cleansing ability and produces a luxurious amount of fluffy lather. However, if you go overboard with using myristic acid, it could lead to drying up of the product.

Besides the above listed fatty acids, there are several other forms of acids which are used in soaps. Salicylic acid is a commonly used acid in soaps and other cosmetics for its acne fighting properties. It has good exfoliating properties which are effective against acne. Kojic acid is used for lightening the skin. Regular use of kojic acid soap is known to reduce pigmentation, however one must not discontinue the use of this soap. Etidronic acid in soap is used to counter the undesirable effects of metal ions in certain soap ingredients. It is also used as a binding agent in several other cosmetic products.

The type of acid in soap is basically dependent upon the specific use of the soap. The proportions of the above listed acids also vary according to the type and purpose of the soap.