A dispersion is a heterogeneous system consisting of a dispersed phase and a continuous phase.

In cosmetics, the dispersed material may be a pigment, mineral, powder, active ingredient or liquid droplet.

Examples include pigment dispersions in foundations, mineral dispersions in sunscreen products and solid particles suspended in exfoliating products.

Stability

The stability of a dispersion depends on particle size, density, viscosity, surface chemistry and interactions between particles.

Particles can aggregate, sediment or float if the formulation does not provide sufficient stabilization.

Dispersing agents, rheology modifiers and appropriate processing can improve physical stability.

Formulation Considerations

Particle size distribution is particularly important. Smaller particles generally provide a larger surface area and may require more dispersing agent.

The final dispersion should be evaluated for uniformity, sedimentation, agglomeration and changes during storage.

References

Barel, A. O., Paye, M. and Maibach, H. I. Handbook of Cosmetic Science and Technology.

Lachman, L., Lieberman, H. A. and Kanig, J. L. The Theory and Practice of Industrial Pharmacy.

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