Topping is when wine is added to a barrel to eliminate any space caused by evaporation or absorption. Because wood is slightly porous, small amounts of wine are absorbed into the barrel and eventually evaporate into the atmosphere. This is especially the case with wines aged in new oak barrels.

It’s important to keep barrels topped in order to prevent oxidation and the development of bacterial spoilage. Depending on how quickly evaporation takes place, most wineries have a regular barrel topping regime that takes place every two to four weeks.