Aims: The physicochemical stability of cosmetic emulsions is crucial for successful commercialization and consumer satisfaction. This study presents an innovative protocol that combines rheology, turbidimetry and granulometry to predict emulsion stability more efficiently. Materials and Methods: Industrial emulsions, including some commercial products, were selected to compare stable and unstable samples with minimal formulation differences. Granulometry, turbidimetry and rheology assessments were used to evaluate physical and structural properties. The collected data were subjected to advanced statistical analysis using experimental design methods. Results: Granulometry, turbidimetry and rheology each effectively distinguished stable from unstable emulsions. Stable emulsions maintained a constant median particle size, while unstable samples exhibited significant increases. Viscosity changes were observed only in unstable emulsions. Turbidimetry showed a Turbiscan Stability Index (TSI) >3 for unstable emulsions and <3 for stable ones. Notably, this combined protocol identified instability as early as 8 days—much faster than standard ISO methods, which require up to 30 days. Conclusions: Integrating granulometry, turbidimetry and rheology with advanced data analysis enables a rapid, reliable and sensitive prediction of cosmetic emulsion stability. This approach overcomes the limitations of traditional testing by allowing earlier detection of instability, improving formulation development, quality control and time‐to‐market. Future work will assess the protocol's applicability to a wider range of emulsion types.

Standard ISO testing of cosmetic emulsions offers limited insight into the microstructural mechanisms governing long-term stability. We hypothesize that a single weight-percent increase in emulsifier concentration is sufficient to determine, through its effect on inter-bilayer junction connectivity, whether the lamellar gel network consolidates or fails. To test this, we apply a two-tier strategy combining ISO/TR 18811 testing and Turbiscan turbidimetry with rheology, laser diffraction, and AI-assisted polarized light microscopy, on two oil-in-water emulsions structured by a lamellar gel network and stabilized by Cetearyl Alcohol/Cetearyl Glucoside at 2 wt% (Emulsion A) and 3 wt% (Emulsion B) over 30 days of storage. First-tier testing distinguished formulations only at Day 30; Turbiscan index values (2.64, 1.78) stayed below threshold throughout. The second-tier protocol resolved structural divergence from Day 8 to 15, two to three weeks earlier. In Emulsion A, a transient birefringent fraction (51.5% at Day 8) preceded network disruption, droplet coalescence, and a drift of the loss tangent toward more liquid-like values. In Emulsion B, birefringence expanded to 98.4% by Day 30 and the loss tangent declined to 0.325. These results indicate that a 1 wt% difference in emulsifier concentration, within a range of industrial use, is sufficient to determine whether the lamellar gel network consolidates or fails, and that combining rheology, laser diffraction and AI-assisted microscopy resolves this divergence two to three weeks before conventional ISO criteria are met.