Wetting of cosmetic powders and pearl pigments

Interfacial Chemistry Determination of Powder Wettability and Dispersion Stability

Most cosmetic products contain powders and pigments to color, protect the skin, or aid in cleansing. Dispersants in the form of surfactants ensure fine distribution of the powder and stabilization of the mixture, and accordingly, the powder surface is usually modified prior to manufacture to match it with the liquid. Chemical measurements of liquid and powder surfaces aid in quality control and new product development.

Determination of liquid wetting by measuring surface tension

In aqueous cosmetics, surfactants produce stable, finely dispersed mixtures by reducing surface tension to improve powder wetting. Our tensiometers measure the surface tension reduction effect of surfactants with high precision.

In order to ensure good compatibility with the skin, it is generally necessary to ensure that the content of surfactants is relatively low. Our instrument fully automatically measures the efficiency of surfactants based on critical micelle concentration (CMC) measurements. At this concentration, the surface is completely covered with surfactant molecules. At concentrations higher than CMC, clusters of surfactant molecules, ie micelles, are formed in the solution, which is a determinant of the cleaning action. The surface tension above the CMC will not decrease further and it is an important parameter for optimal surfactant dosage.

Contact angle measurement to determine powder wettability

Our tensiometers measure the wettability of powders on the basis of the contact angle, and also measure data on the surface energy and its polar components, providing information about the closely related liquid phase. As an alternative, the contact angle of the droplet on the powder layer can also be measured optically.

For products such as nail polish or lipstick, which are usually coated with partially polar inorganic powders for use in hydrophobic environments, the effect of this pretreatment can also be quantified by the powder contact angle.