Cloud point

The Cloud point of a nonionic surfactant or glycol solution is the temperature where the mixture starts to phase separate and two phases appear, thus becoming cloudy. This behavior is characteristic of non-ionic surfactants containing polyoxyethylene chains, which exhibit reverse solubility versus temperature behavior in water and therefore "cloud out" at some point as the temperature is raised. Glycols demonstrating this behavior are known as "cloud-point glycols" and are used as shale inhibitors (see Talk). The cloud point is affected by salinity, being generally lower in more saline fluids.

Cloud Point is the temperature at which waxy crystals in an oil or fuel form a cloudy appearance. Cloud point is an indicator of the tendency of the oil to plug filters or small orifices at cold operating temperatures. (Definition taken from http://www.dcpetroleum.com/)