Carcavelos is a vinho generoso, or strong fortified wine, produced from a blend of up to nine different white and red varieties (for the whites: Arinto, Gallego Dourado and Ratinho are most common; for the reds: Trincadeira, Negra Mole and Castelão). The fermentation can be arrested via mutage, or the wine can be fermented dry and. subsequently fortified with viho abafado (a fermented grape must, preserved by the addition of neutral alcohol), bringing it to 18-20% abv, typically with 80-95 g/l of residual sugar, similar to the sweetness level of Boal Madeira. The wine must then be aged a minimum of three years in cask, but elevage can range from five to 20 years, the wine becoming oxidative in character, with barrels more or less topped-up, depending on the style of the producer.