Wetting agents are substances that reduce the surface tension of water to allow it to spread drops onto a surface, increasing the spreading abilities of a liquid. Lowering the surface tension lowers the energy required to spread drops onto a film, thus weakening the cohesive properties of the liquid and strengthening its adhesive properties. The simplest way to improve water take up by hydrophobic soils is to use a soil wetting agent. When organic matter on the soil breaks down it leaves a waxy coating on the soil particles. Wetting agents are like detergents. They overcome that waxing coating and allow water to penetrate into the pore spaces between. There are four main types of wetting agents: anionic, cationic, amphoteric, and nonionic.
- Anionic, cationic, and amphoteric wetting agents ionize when mixed with water.
- Anions have a negative charge, while cations have a positive charge.
- Amphoteric wetting agents can act as either anions or cations, depending on the acidity of the solution.
- Nonionic wetting agents do not ionize in water. A possible advantage for using a nonionic wetting agent is that it does not react with other ions in the water, which could lead to formation of a precipitate.