The process of making mezcal has not changed much since the Spanish arrived in Mexico in the early 1500's and brought with them distillation technologies. The Aztecs near the mountain top settlement of Monte Alban in Oaxaca had cultivated a certain species of agave plant for juice which they would ferment into what they called pulque. The Spaniards, wanting something much more potent, began to experiment with agave.
Mezcal vs. Tequila:
Mezcal is made from the agave plant. The agave is also used to make tequila but in a different process. While tequila is made exclusively in the northwestern state of Jalisco, mezcal is exclusive to Oaxaca. Although tequila is most popularly consumed in the margarita, mezcal is almost exclusively served as a shooter, with or without a lick of salt and bite of lime.
The Manufacturing Process:
The long, pointed-leafed agave must be allowed to grow for a minimum of eight years before it is plucked from the earth and its pineapple-like core is separated.
The cores of hundreds of agave plants are baked in a sunken pit for a few days, then mashed with a horse-drawn grinding wheel. The mashed remains are put in a huge barrel with water to ferment, followed by distillation in clay or bronze tanks covered by dirt and heated by logs. Steam passes through ducts and the condensation yields mezcal.
In contrast, tequila also uses the baked cores. A sweet juice is then extracted by steaming and compressing the cores. The juice is fermented for several days and then distilled at low proof, and then double or even triple distilled.