Term for the sulphurization (preservation, sterilization) of empty wooden wine barrels by sulphur firing. Other designations are wrapping, wrapping, empty cask firing and sweet firing. The barrel must be completely dry. The required number of sulphur cuts (or sulphur rings) is placed on a baking wire (galvanized and annealed), this is hung in the middle or in the lower third of the barrel and then the sulphur is burnt off. The resulting sulphur dioxide kills bacteria and fungi. As a rule, a barrel of two to three hectolitres requires one cut of three grams, a piece barrel of 1,200 litres requires four cuts. Every month a further cut of half a quantity must be made.
If used too intensively, considerable accumulation of sulphuric acid in the barrel can occur, which can cause the wine defect sulphuric acid firn. Improper use may cause the basis for the wine defect Böckser (Schwefelböckser). Before filling with wine, the barrel must therefore be thoroughly watered (cleaned) to leach out the sulphur dioxide. Ozone is also used to disinfect or sterilise barrels. Before the use of potassium pyrosulphite, the usual sulphurisation practice for wine was to fill the barrel with wine and then to allow the wine to absorb the sulphur dioxide. A longer-term effective barrel conservation method is wet conservation.