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The cleaning process

Cleaning or detergent action is entirely a matter of surfaces.

Wet cleaning involves an aqueous medium, a solid substrate, soil to be removed, and the detergent or surface-active material.

An oversimplified differentiation between soft- and hard-surface cleaning lies in the magnitude and kind of surface involved.

One gram of cotton has been found to have a specific surface area of Af.

In contrast, a metal coupon Af in size would have a magnitude from 100,000 to a million less.

Even here there is room for some variation, for metal surfaces vary in smoothness, absorptive capacity, and chemical reactivity.

Spring used a Brush surface-analyzer in a metal-cleaning study and showed considerable differences in soil removal, depending upon surface roughness.

There are considerable differences between the requirements for textile and hard-surface cleaning.

Exclusive of esthetic values, such as high- or low-foam level, perfume content, etc., the requirements for the organic active used in washing textiles are high.

No matter how they are formulated, a large number of organic actives are simply not suitable for this application, since they do not give adequate soil removal.

This is best demonstrated by practical washing tests in which cloth articles are repeatedly washed with the same detergent formulation.

A good formulation will keep the clothes clean and white after many washings ; ;

whereas, with a poor formulation, the clothes exhibit a build-up of `` tattle-tale grey '' and dirty spots -- sometimes with bad results even after the first wash.

Since practical washing procedures are both lengthy and expensive, a number of laboratory tests have been developed for the numerical evaluation of detergents.

Harris has indicated that two devices, the Launder-Ometer and Terg-O-Tometer are most widely used for rapid detergent testing, and he has listed the commercially available standard soiled fabrics.

Also given are several laboratory wash procedures in general use.

The soiled fabrics used for rapid testing of detergent formulations are made in such a way that only part of the soil is removed by even the best detergent formulation in a single wash.

In this way, numerical values for the relative efficacy of various detergent formulations can be obtained by measuring the reflectance ( whiteness ) of the cloth swatches before and after washing.

Soil redeposition is evaluated by washing clean swatches with the dirty ones.

As is the case with the surface-active agent, the requirements for builders to be used in detergent compositions for washing textiles are also high.

Large numbers of potential builders have been investigated, but none have been found to be as effective as the polyphosphates over the relatively wide range of conditions met in practice.