Werner Skrypzak

Optical methods for measuring the pearlescent effect in toiletries.

Pearling agents used to improve the appearance of toiletries are generally judged visually, as it is difficult to devise suitable quantitative tests. If a pearling agent is added to a stirred liquid, moving light and dark patches may be seen. A method has been developed to put this simple test on a quantitative basis. The reflected light is measured using a fibre optic probe. An on‐line computer calculates the ratio of the standard deviation to the mean of the intensity; this is a measure of the pearlescent effect. By combining such measurements with turbidity data, a two‐parameter description of the appearance of the product is obtained. The method may be used for quality control, comparison of commercial formulations or to monitor changes during storage.