Grapes are harvested by hand, crushed and then may be fermented in temperature controlled wood, concrete, or stainless steel vats of varying size depending on the style of the vintage. Léoville-Las Cases also employs a state of the art reverse osmosis machine to help extract excess water from the grape must in a rainy vintage. Use of this machine is considered legal, but highly controversial, and while Léoville-Las Cases is not the only estate to employ this technique, few estates admit to their use. After processing and fermentation, the wine is transferred into oak barrels for 18–20 months of aging before being fined with egg whites and bottled.