Storage of wine in a barrel with the purpose of subjecting it to a maturation process. Barrels can be made of different materials such as stainless steel, wood, concrete or ceramics, but barrel ageing usually means a wooden barrel. The size of the barrel, the age of the barrel, the type of barrel wood and the way it is made have a great influence on the course and length of the ageing process. The type of bar rel ultimately used depends above all on the desired style of wine. Very often, however, wine descriptions in connection with vinification do not clearly indicate the type of wooden barrel in which the wine was matured. This is because the type of ageing does not have to be specified by wine law.