The base of a mature agave plant is steamed in order to extract the sap. The sap ferments for about 10 days, producing "mother pulque". This is then added to fresh sap and allowed to ferment, producing pulque (wine). The pulque is then double-distilled in pot stills, and the resultant vino mezcal can be exported immediately as a "white" liquor, or it may be aged in oak casks to produce an añejo or aged product.
For tequila aficionados, let's set the record straight on mezcal and tequila. Tequila is to mezcal what Cognac is to brandy; that is, tequila is a superior form of mezcal. Tequila is produced only in two designated regions of Mexico, one surrounding the town of Tequila, the other in the area of Tepatitlan. Mezcal is produced in numerous regions throughout Mexico.
While tequila is made only from a blue-colored agave plant, specifically Agave tequilana weber, mezcal can be made from different varieties of agave. Production of tequila is governed by stringent quality standards that are not applied to mezcal. Ordinary tequila is considered "white" tequila.