Phase separation can occur in emulsions, suspensions and other multiphase cosmetic systems.

In an emulsion, separation may appear as oil separation, water separation, creaming, sedimentation or complete breaking.

The visible symptom does not necessarily reveal the underlying mechanism.

Causes

Possible causes include inadequate emulsification, excessive droplet size, poor emulsifier selection, coalescence, phase inversion, incompatible polymers, crystallization and temperature stress.

Chemical degradation or microbial contamination can also indirectly contribute to physical instability.

Troubleshooting

The first step should be identifying the mechanism responsible for the separation.

Increasing viscosity may reduce creaming but will not necessarily prevent coalescence. Similarly, increasing emulsifier concentration may not solve a problem caused by incorrect processing.

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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