Over the last 20 years, the technology of cooling water deposit control has advanced significantly. There are presently numerous different deposit control agents available that are used to prevent the formation of the various scales and foulants discussed in the previous section. Prior to discussing the actual composition of these materials, it is necessary to understand the different mechanisms by which these materials function. In general, cooling water deposit control agents function via one or more of the following mechanisms: flocculation, scale crystal distortion, dispersion, sequestration, and surfactancy. Since many of the materials that function via these mechanisms are polymers, we will first develop differences between the various types that exist.