Soaps & Detergents: Chemistry To understand what is needed to achieve effective cleaning, it is helpful to have a basic knowledge of soap and detergent chemistry. Water, the liquid commonly used for cleaning, has a property called surface tension.
In the body of the water, each molecule is surrounded and attracted by other water molecules. However, at the surface, those molecules are surrounded by other water molecules only on the water side. A tension is created as the water molecules at the surface are pulled into the body of the water. This tension causes water to bead up on surfaces (glass, fabric), which slows wetting of the surface and inhibits the cleaning process. You can see surface tension at work by placing a drop of water onto a counter top.