Mezcal is a distilled alcoholic beverage made from the agave plant, a slow-growing succulent native to Mexico and Texas. Mezcal was first produced in the 16th century by the conquistadors, who, as invading soldiers often did, made getting drunk a top priority in the hostile territory they were occupying and used whatever they could find locally to produce alcohol.
According to tradition, there are generally three ways to produce mezcal. The first is that all buy mezcal must be made from 100% agave with no added sugar. Mezcal can be made in a variety of ways, including ancestral, artisanal, and industrially produced.
Traditionally, ancestral mezcal is distilled in clay pots called ollas de barro that differ from those termed artisanal. In this method, the agave is cooked in a pit and crushed using a mallet or stone mill. The distillation of ancestral mezcals in stainless steel columns is not permitted.
Mezcals that are certified as artesenal fall into this category the most. These producers use ancestral methods but do not use autoclaves, diffusers, or column stills.
Finally, we have industrially produced mezcal, which allows modern tequila production methods to be used. Mezcals made this way are often criticized by those who appreciate ancestral and artisanal mezcals, as they are made by cooking the agave in autoclaves, extracting its juice with a diffuser, and distilling it in stainless-steel columns.
So these are the ways which is determining the mezcal quality. So find the right type of mezcal to buy for your preference.