Manufacturers constantly monitor the quality of their detergents, and they utilize the same testing methods to assess the effectiveness of new products. In one method, light is shined onto a piece of fabric that has been soiled and then washed in the test detergent
The amount of light reflected, compared to the amount reflected by a sample of the original fabric, is a measure of cleanliness. A reflection rate of 98 percent is considered quite good and indicates that the detergent has cleaned properly.
Another method involves laboratory burning of a small amount of material that has been soiled and then laundered. The weight of the ashes, plus the weight of the gaseous results of the burning, reveal how much of the dirt remained in the fabric after laundering. A result that is much higher than a clean test sample indicates that a significant amount of dirt was retained in the laundered sample. Naturally, the goal is to come as close to the weight of a clean control sample as possible.