To measure the surface charge of hair, the so-called zeta potential is determined. The zeta potential of untreated hair is negative at neutral pH and thus represents the starting point for any form of hair care. A reversal of the surface charge, as when using a conditioner, begins at the so-called isoelectric point. This point indicates the pH value at which the zeta potential is 0 mV.
This takes advantage of the fact that macroscopic materials such as hair develop a charge on their surface when in contact with liquids, which can be either negative, positive or neutral. The charge behavior is an indicator of all changes to the material surface and is thus an important parameter for the characterization and development of suitable products.
The charge behavior and its changes are described using the zeta potential.
Hair samples and their interaction with various care products can be followed in real time by means of the zeta potential analysis. These findings can be incorporated directly into the development of appropriate hair care products for different hair types.
In the cosmetics industry, for example, the importance of producing suitable care products that take into account the complexity of the hair structure has increased dramatically, in part because of rapidly increasing competition. By now it is thus just as important to understand the effect of different hair treatments, as to adapt also to changes in hair structure by permanent treatments such as dyeing or bleaching and to develop suitable products.
The SurPASS™ 3 from Anton Paar can measure the surface charge of samples, and can therefore be used for the analysis of hair surfaces to create ideal hair care products.