Stoppers to be used must be chosen considering the bottling machine, the type of bottle and the size of the neck, as well as the type of wine to be bottled and the circuit expected for the wine on the market (shipping and turnover time).
- For most wines, and keeping in mind the internal size of the neck, the diameter of the natural stopper should be at least 6 mm larger than the smallest diameter of the neck. For prolonged maturation periods, a diameter superior to 6mm is advisable, but should not exceed 8mm.
- If using technical or agglomerated stoppers, the size should be 1 mm less when selecting the diameter due to their higher density.
- The stopper should be both longer and larger in diameter when the ageing time scheduled for the wine in the bottle is longer. However, in relation to the length of the stopper, the space required between the lower end and the surface of the wine should always be observed (a minimum of around 15 mm) so as to have an expansion chamber to compensate for any expansion of the wine due to thermal effects.
- For wines with some gas (internal pressure above normal), stoppers should be chosen with a larger diameter than those recommended for still wines. In general, and as an example, for wines with about 1 bar internal pressure, a diameter of 8mm larger than the smallest internal diameter of the neck is recommended.