The Difference Between Soaps & Detergents


Soaps are fats that have been treated with alkali (sodium or potassium hydroxide) to form a salt. A soap is technically a detergent because a detergent is “a product which is capable of cleansing”. What most people commonly call a detergent is a synthetic or semi-synthetic surfactant. Many of these synthetic detergents are in-fact derived from natural products such as plant oils and fats as the “hydrophobic” component and sugars, alcohols or betains for the “hydrophilic” component, so many of them are extremely biodegradable and made from renewable resources.


Soaps have some major disadvantages over modern detergents:

• Soaps have limited detergency power. Because of their chemical structure soaps are poor at penetrating and dissolving certain types of soil such as heavy fats and proteins.

• Soaps react with metals (calcium, magnesium, iron etc.) that are dissolved in the water and form very insoluble precipitates (soap scum) that can deposit onto surfaces and are very hard to remove.

• Soap has lower solubility in cooler water. Therefore less cleaning power and harder to rinse off.


Modern detergents have many advantages over soap:

• Greater cleansing efficiency because the structure of the surfactant can be tailored to the type of soil and the surface to be cleaned.

• They do not react with heavy metals and other salts so they will not produce an insoluble residue.

• Greater solubility in water at different temperatures, therefore better cleaning and rinsing.

• Higher efficiency as “wetting” agents means they can penetrate soils that have been dried onto surfaces or contain high levels of heavy fats and oils.