First the baskets of grapes were piled high in plaster-lined compartments called tabulata. Juice which exuded from the grapes under the pressure of their own weight was used to make a sweet, heavy wine of the highest quality-what the Romans called lixivum mustum or protropum.
Such a wine invariably was white because it was prepared from juices that had only brief contact with the crushed skins of the grape harvest, irrespective of whether the grapes themselves were of a white or black variety. There were some fine dark wines in the Roman world, however, notably those produced on the Greek island of Thasos where the grapes were allowed to shrivel in several clusters before being processed as described here. To produce red wine today, however, vintners deliberately will include the skins of black grapes in the fermentation process, extracting both the pigmentation and the tannins in them that provide the wine with an astringency now deemed desirable.