Décantation

Décantation is a separation process in which a liquid is carefully poured from a mixture that contains a denser phase, such as a solid sediment or a heavier liquid, into another container, leaving the heavier phase behind. The technique relies on differences in density and the ability to tilt or decant without disturbing the settled material.

In chemistry, decantation is used to remove liquid from a precipitate after filtration, to wash or separate solids from liquids, and to separate immiscible liquids by gravity. It can be performed as gravity decantation, by slowly pouring the liquid off after allowing the mixture to settle, or as centrifugal decantation, where a centrifuge accelerates the separation to speed up the process.

In winemaking, décantation refers to pouring wine from its bottle into another vessel to separate the clear liquid from sediment (lees) and to expose the wine to air, which can enhance aroma and flavor. Decanting is commonly employed for red wines with substantial sediment and for older wines that may have collected deposits.

Advantages of décantation include simplicity, low equipment requirements, and gentle separation that minimizes disturbance to the remaining phase. Limitations include incomplete separation of fine particles or emulsions, potential loss of the desired liquid with the sediment, and, in wine, the risk of oxidation or aroma loss if done excessively.

Etymology traces the term décantation to French, with roots in Italian decantare and related Latin forms. It is closely related to, but distinct from, filtration and centrifugation, which provide different means of achieving separation.