Term for the loss of liquid in a wine container caused by evaporation, which occurs mainly in wooden containers but also in bottles sealed with natural corks. Wooden barrels are not absolutely leak-proof compared to tanks made of stainless steel, glass or ceramics, but there is a certain exchange of substances (liquid and also oxygen) in both directions (both outwards and inwards). With old wooden barrels, leaks, especially between the barrel staves, can result in relatively high shrinkage. Depending on the type of wine, the resulting empty space in a barrel must be regularly refilled, especially with young wine, to prevent oxidation. The tightness of the bunghole or the position of the bunghole on the barrel also has an influence. Water and alcohol escape to varying degrees through the wood pores. With water molecules, this occurs more quickly, but this also depends on the air humidity, air pressure and air temperature.