A ripe organic grape is full of natural sugars and there are wild yeasts living on its skin. As soon as the skin of the grape is broken, fermentation can begin.
To make wine, all the winemaker has to do is collect his grapes and gently crush them, releasing the sugary juice and exposing it to the yeasts.
Fermentation will continue until all the sugar has been turned into alcohol or the level of alcohol in the juice reaches around fifteen percent, whichever is sooner.
At around fifteen percent alcohol, the yeasts will die naturally and any left over sugars will remain in the wine.