COLOUR COSMETICS 57
fibrillar network maintained particle suspension under centrifugal forces of at least 3 xG. Increasing the MFC concentration to 2 wt% significantly improved stability, with all pigment loadings remaining suspended at forces of at least 12 xG. At 3 wt% MFC, no particle separation was
observed at 12 xG, and the dispersions remained stable up to approximately 70 xG before separation began. Particle separation was first observed at approximately 70 xG. Interestingly, the dispersion stability was
largely independent of pigment concentration within the investigated range (0.5–2 wt%), suggesting that the fibrillar network possessed sufficient structural integrity to immobilize increasing pigment loadings without a measurable reduction in performance. Visual observations during centrifugation
further revealed that although the MFC network itself gradually compacted under increasing centrifugal force, the iron oxide particles remained embedded within the fibrillar matrix rather than separating from it. This behaviour indicates that the pigment
particles are physically entrapped within the three-dimensional cellulose network rather than suspended solely through increased viscosity. Consequently, substantially higher external forces are required to overcome the interactions between the pigment particles and the MFC network. These findings provide experimental evidence
for the proposed stabilization mechanism of MFC. The interconnected fibrillar network acts as a three- dimensional scaffold that imparts both yield stress and mechanical support, effectively restricting particle mobility and reducing sedimentation. This stabilization mechanism is particularly
relevant for formulations containing high-density inorganic pigments, where preventing particle settling is essential for maintaining formulation homogeneity, consistent colour development, and long-term storage stability.
Figure 2: Pigment dispersion in aqueous suspension without (left) and with (right) microfibrillated cellulose
TABLE 1 % in dispersion 0.5% particles
1% MFC 2% MFC 3% MFC
3g 12g ≥12g
1% particles 3g
12g ≥12g
2% particles 3g
12g ≥12g
Table 1: Dispersion stability of iron oxide particles in aqueous MFC dispersions after centrifugation. Values indicate the minimum centrifugal force at which the pigment remained homogeneously suspended within the MFC network
Relationship between dispersion stability and optical performance Although dispersion stability and optical performance are often evaluated separately, both properties are closely related. Stable pigment dispersions maintain a homogeneous particle distribution throughout processing, storage, and application. This homogeneous distribution directly
influences the optical behaviour of the formulation by reducing localized differences in pigment concentration. Accordingly, improvements in dispersion stability can translate into more uniform colour development, enhanced colour intensity, and improved visual appearance of the finished cosmetic product. The experimental sedimentation study therefore
provides a mechanistic explanation for the aqueous formulation results presented in the following section. Additionally, the effect can be observed in anhydrous formulations such as lipstick. The improved optical properties observed in the brow cream and bronzer formulations can be interpreted as a direct consequence of the enhanced pigment stabilization achieved by the fibrillar cellulose network.
Performance evaluation Lipstick formulations In lipstick formulations, the incorporation of microfibrillated cellulose resulted in increased colour intensity and improved coverage. The bulk formulation appeared darker and more saturated than the control formulation, indicating improved pigment distribution and enhanced optical appearance. The darker appearance of the lipstick bulk
suggests that pigment particles remained more uniformly distributed throughout the formulation. Homogeneous pigment dispersion reduces localized variations in pigment concentration, resulting in more consistent light absorption and enhanced visual colour intensity. Additionally, incorporating MFC reduced the
sweating effect, a phenomenon characterized by the formation of small oil droplets on the surface of the finished lipstick. These results demonstrate improved pigment dispersion within the formulation.
Brow cream formulations Similar results were observed in brow cream formulations. Samples containing microfibrillated cellulose exhibited a deeper and more vivid colour than formulations without the ingredient, which appeared lighter and less saturated. The deeper colour observed in the
formulation containing MFC is consistent with a more homogeneous distribution of pigment particles throughout the continuous phase. Improved dispersion minimizes localized pigment agglomerates and enables more uniform deposition of pigments during application, thereby contributing to greater colour consistency.
Figure 3: Bulk lipstick formulations with (bottom) and without (top) microfibrillated cellulose
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Figure 4: Lipstick comparison containing microfibrillated cellulose and placebo formulation with MFC
without without with MFC October 2026 PERSONAL CARE MAGAZINE
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