Precipitates

precipitates, solids which are deposited on the bottom of barrels, casks, tanks, or vats by wine stored in them.

Technically, precipitates are solids which deposit from solutions because of reactions or temperature changes, and differ from sediments, which are suspensions of solids which settle from the mixture when agitation ceases. Technically, therefore, the stem, pulp, and skin fragments and the seeds and dead yeast cells which settle after fermentation as gross lees are not precipitates, while subsequent deposits of tartrates and oxidized phenolics are. Practical winemakers, however, tend to classify both groups as precipitates, along with colloids.