To clean and remove stains from clothes and other fabrics, detergents use surfactants as wetting agents. A Wetting agent refers to a substance that makes a liquid – in the case of the use of detergents, water – “wetter”, because the surface tension is lessened greatly and the water’s molecular structure is loosened, allowing it to work on stains and dirt. By itself, water cannot thoroughly clean fabrics, especially ones with oily or greasy stains. Remember the saying “oil and water do not mix”? That’s because of the surface tension.
Surfactants work as wetting agents through a process which is referred to as adsorption. Adsorption is when the surface of the water collects molecules and atoms from the surfactant which then in turn lowers the surface tension of the water. This accumulated atoms and molecules form a very thin, but visible translucent film over water that is mixed with detergent. This is why it is very effective for detergents to use surfactants as wetting agents. Through scrubbing, or even prolonged soaking, dirt and any stains in the fabric get dissolved and can be washed away with the remnants of the detergent and everything else
There are many different types of surfactants, each one different and the degrees in which they are put into together in a particular brand of detergent depend on the manufacturers who have specific functions in mind. Anionic surfactants are the most common type, which strips oil and greasy stains but is weak with hard water. Cationic surfactants, on the other hand, are used as rinse fabric softener or as an internal component to a detergent that had built in fabric softener. Non-ionic surfactants are added into a mix to negate the effects of hard water.
Using surfactants as wetting agents is a very good way for detergents to do their job and give you clean clothes and fabric.