Advanced Characterization of Soft Cosmetic Film Deposits with X‐Ray Microtomography

Cosmetic materials are complex soft compounds, including pigments, emulsifiers, film-formers, and fillers. After evaporation or absorption, they form a residue of inert ingredients called the cosmetic film. This thin layer, deposited on the skin, enhances complexion by smoothing texture, concealing imperfections, and evening skin tone. However, visualizing and characterizing these fragile films on real skin-cosmetic interfaces remains challenging, as they are prone to damage during analysis. Current evaluation methods rely on subjective approaches, such as consumer feedback, color studies, and optical observations, lacking quantitative insights into the relationship between physical properties and sensory experiences. This study introduces X-ray microtomography as a quantitative tool to examine liquid foundation films deposited on an artificial skin substrate. By analyzing parameters such as coverage thickness, profile topography, and skin deformation, this method differentiates cosmetic products at the microscale. Additionally, X-ray microtomography effectively visualizes emulsion droplets in complex formulations, enabling accurate quantification of key parameters like drop size distribution, critical for product texture and stability. These findings demonstrate the potential of X-ray microtomography as a robust, objective approach for studying cosmetic formulations and other soft material-based films, bridging the gap between physical properties and product performance while providing insights for process development and quality improvement.