lees stirring, or bâtonnage, as it is called in French, is the once fashionable winemaking operation of mixing up the lees in a barrel, cask, tank, or vat with the wine resting on them. It is an optional addition to the process of lees contact and is often employed, particularly for whites which have undergone barrel fermentation. As the French name suggests, such stirring is usually done with a stick, although some racking systems allow the barrel itself to be rotated in situ.
Lees stirring is done partly to avoid the development of malodorous hydrogen sulfide. Unless a thick layer of lees is stirred, oxygen does not reach the bottom layer and strong enough reducing conditions develop to change any small amounts of sulfur into hydrogen sulfide (see lees contact).
