The process of debilitating fermentation begins earlier for Malmsey and Boal. The drier types - Verdelho and Sercial are fermented longer to create the drier character. The longer the juice is allowed to ferment , the drier the wine will be. The application of excessive heat or cold also affect the fermentation, which must be controlled to obtain precisely the quality of wine desired.
Ample quantities of wine alcohol, added massively, halt fermentation, and the natural sweetness of the wine is retained. The treatment of alcohol to the juice cleans the wine, leaving all impurities to settle to the bottom. This prepares the wine to be heated to the style that is so characteristic of Madeira wines.