What do you do with your dirty linen and clothes? Wash them with detergents, of course! The word detergent usually refers to synthetic detergents, which have a different chemical makeup than soap.

Detergents contain surfactants which increase the wetting ability of water by lowering its surface tension. With its surface tension reduced, water penetrates the soiled material more completely.

A surfactant has two distinct parts with different characteristics. One part of each surfactant molecule is hydrophilic (attracted to water), but the other part is hydrophobic (repelled by water). The hydrophobic parts of surfactant molecules attach themselves to any surface other that water. Many hold on to the partcles of dirt in the soiled material. At the same time, the hydrophilic parts pull away from the material and pull the dirt towards the wash water.

The Mechanical agitation (motion) of a washing machine, or the movement caused by rubbing by hand, helps break up the dirt. It also helps the hydrophilic parts of the surfactant molecules pull the dirt particles from the material and into the water.

Once the dirt particles are in the water, the thin layer of surfactant molecules around the paricles keeps them separated. They prevent the dirt from settling on the washed material until it is finally rinsed.

NOTE: Believe it or not, a Sumerian text dating back to 2,500BC described the manufacture o a detergent product.