To prepare a naturally sweet wine (generally of the small grain Moscatel (Muscat) variety), the grapes must be over-ripe with a high sugar content. Once the grape must being fermented is considered to have a good acquired alcohol / sugar balance, the process is halted without allowing all the sugar to change to alcohol. To do so, the wine is racked, cooled, filtered and sulfated. Before aseptic bottling, a strict amicrobic filtration should be performed to eliminate any possible micro-organisms. No alcohol should ever be added (fortification) .
This is obtained by adding vinous alcohol to fermenting grape must or wines (providing that the latter come from small berry grapes of the Moscatel de Grano Menudo variety), or from mixing vinous alcohol with grape must. If it is to undergo an ageing process, it is also possible to add directly heated grape must concentrate.