is the suspension of finely divided particles, 5 to 5000 angstroms in size, in a gas or liquid, that do not settle and are not easily filtered. Colloids are usually ionically stabilized by some form of surface charge on the particles to reduce the tendency to agglomerate. A lubricating grease is a colloidal system, in which metallic soaps or other thickening agents are dispersed in, and give structure to, the liquid lubricant.