congealing

Congealing is the transition of a liquid or semi-liquid substance into a solid or semi-solid state, typically as a result of cooling, solvent loss, or a chemical change. It describes how a material becomes set, thickened, or gel-like rather than simply turning into a crystalline solid. Depending on the system, congealing can involve crystallization, gelation, or the formation of a solid network.

The process generally proceeds through nucleation, where small stable structures form, followed by growth of those structures. The outcome—crystalline solid, amorphous solid, or a gel network—depends on factors such as temperature, cooling rate, pressure, concentration, and the presence of impurities or additives. Solvent removal or chemical reactions can also trigger congealing in some mixtures or formulations.

Common examples include fats in dairy and culinary contexts, which congeal when refrigerated to form a solid fat phase; chocolate that sets as it cools; sauces or desserts containing gelatin, starch, or pectin that form gels; water turning into ice; and waxes or paraffins that solidify from liquids. Some emulsions or colloidal systems develop a semi-rigid matrix during aging or processing.

Distinctions from related terms are important: freezing is a temperature-driven form of solidification; coagulation involves the aggregation of particles; crystallization implies an orderly lattice. Congealing is a broader term that covers solidification via crystallization, gelation, or network formation, and is often used to describe the set or solidification point of a material.