bentonite, fining agent based on a montmorillonite clay found principally in the state of Wyoming in the western United States, and in many other areas of the world. Like most clays, bentonite is a hydrated compound of aluminium and silicon oxides, but it differs in ways that are useful to winemakers. When mixed with water, it swells and assumes a form that has significant powers of adsorption.
Bentonite, so called because it was first discovered in the Fort Benton rock series, is widely used in the new world to ensure protein stability, particularly to remove heat-unstable proteins from white wines.
