The problems of hard surface cleaning are not nearly as complex. In hard surface cleaning, the inorganic salts are more important than the organic active. Indeed, when the proper inorganic constituents are employed, practically any wetting or surface-active agent will do a reasonably good job when present in sufficient amount in a hard surface cleaning formulation. Hydroxides, orthophosphates, borates, carbonates, and silicates are important inorganic ingredients of hard surface cleaners. In addition, the polyphosphates are also used, probably acting more as peptizing agents than anything else. The importance of the inorganic constituents in hard surface cleaning has been emphasized in a number of papers.

Although there is no question but that the process of washing fabrics involves a number of phenomena which are related together in an extremely complicated way and that these phenomena and their interrelations are not well understood at the present, this section attempts to present briefly an up-to-date picture of the physical chemistry of washing either fabrics or hard surfaces. The purpose of washing is, obviously, to remove soils which are arbitrarily classed in the four major categories given below:

Dirt, which is here defined as particulate material which is usually inorganic and is very often extremely finely divided so as to exhibit colloidal properties.

Greasy soils, which are typified by hydrocarbons and fats (esters of glycerol with long chain organic acids).