In polymer chemistry, materials science, and food science, bloom refers to the migration of one component of a solid mixture to the surface of an article. The process is an example of phase separation or phase aggregation.

Blooming is commonly encountered in polymer additives such as stabilizers.^[1] Many polymers are essentially pure hydrocarbons whereas additives are often significantly more polar, this results their being forced out via hydrophobic forces. The blooming of additives may be desirable or undesirable. For example, the migration of antioxidants to the polymer surface may help it resist degradation. Conversely, the leaching of additives from packaging materials into foods, or the blooming of additives in biomedical devices is often of high concern.^[2] Regulations exist in many counties that require both the levels of blooming and the materials involved to be of a safe level, for example the international symbol for materials approved for food contact is a wine glass and a fork symbol.

• Efflorescence