unblendable

Unblendable is an adjective used to describe a substance or mixture that cannot be blended to form a homogeneous result under ordinary mixing conditions. In everyday language, it often refers to immiscible pairs of substances that separate rather than mix, such as oil and water. In scientific contexts, the property is described more precisely as immiscibility: two liquids that do not form a single phase due to differences in polarity, interfacial tension, or density. When unblendable pairs are combined, phase separation typically occurs, with one liquid forming a distinct layer atop the other.

In chemistry and materials science, the term highlights the practical challenge of achieving a uniform mixture. Emulsions can overcome unblendability temporarily or with stabilization; emulsifiers or mechanical energy can create dispersed droplets of one phase within another, but stability is often limited and depends on conditions like temperature and the presence of surfactants. In cooking and food science, unblendable ingredients are common: oil and water-based components require emulsification or processing to achieve a stable product such as mayonnaise or vinaigrette.

The word is largely informal; in formal writing, immiscible or nonmiscible is preferred. Unblendable emphasizes the outcome of blending attempts rather than a fundamental chemical property in technical terminology. Related concepts include immiscibility, emulsification, and phase separation.