Distillation: Types of Still
There are two categories of still used in the production of artisanal mezcal in Oaxaca: Olla de Barros - traditional clay pots, and Alembiques - European style copper alembics a.k.a. copper pot stills. For the most part a mezcalero’s choice of still is regionally determined, for example in Santa Catarina Minas and Sola de Vega they use clay, while in San Dionisio and Miahuatlán they use copper. As Miahuatlán is our home region, this article will focus on copper alembics and their sub-categories.
In order to understand the function of a copper alembic, it’s first important to cover the basic chemistry behind distillation. Cue distillation 101:
The process of fermentation creates a whole host of chemicals, many of which are categorised as alcohols. Some of these we want in our cup, and some we don’t. The holy grail is Ethanol, the feel-good alcohol we all know and love. While other types of alcohol, notably esters, are important for delivering funky, fruity flavours. Chemicals we generally try to avoid include Methanol, the infamous alcohol which gives you a nasty hangover, and Acetone, which smells like nail varnish remover. All of these chemicals are created in fermentation, so if you want to make strong booze it’s important to capture the friendly chemicals, and dispatch of the unfriendlies. Fortunately, each of these chemicals have different boiling temperatures, so by slowly heating the liquid in a chamber and then condensing the vapours we can isolate the different types of alcohols. This chamber is the still, and the process is distillation.
Unfortunately, its not quite as easy as that. We all know that water boils at 100 degrees centigrade, but this does not mean that water won’t evaporate at lower temperatures – left for long enough an uncovered glass of water will completely evaporate at room temperature. The boiling temperature is the simply the maximum temperature a chemical can reach while remaining a liquid (under normal atmospheric pressure). This doesn’t render the still useless – chemicals with low boiling points will evaporate quicker at low temperatures than chemicals with high boiling points – but it does mean that the process gives you a rough cut of the chemical compounds, rather than something precise.
Fortunately, we have ways of improving the precision of this system. The alembic is a sealed chamber with only a small pipe at the top for syphoning off vapours, so the majority of vapours will condense within the chamber and return to the main body of liquid. By evaporating and condensing multiple times you increase the likelihood of isolating certain chemicals at certain temperatures, and so increase the precision of the process. The bell shape of the top portion of the alembic helps further by circulating vapours within the chamber. Beyond this there are two main methods to increase precision: double distillation and refrescadors.
Double distillation is the method preferred by Atenogenes and Onofre. They distil the ferment once, selecting the portions, or “cuts”, of the distillate which they want to keep, and discarding the rest. The selected cuts after 1 distillation are known as shishe or ordinario, and average roughly 20% alcohol. The shishe then goes back into the alembic for a 2nd distillation, and by selecting particular cuts of this second run you are left with a mezcal high in the chemicals you want, and low in the ones you don’t.
Felipe, along with many other producers in Miahuatlán, prefer the refescador method. This involves surrounding the top portion of the alembic with a metal bucket which is filled, and intermittently refreshed, with cold water. This keeps the top portion of the still cooler, increasing the rate of condensation, and so the precision of cuts of the distillate. It’s a slower process and requires more fuel than the first run of a standard alembic, but provides sufficient precision to create a finished product in just one distillation.
The two process have different influences on the profile of the resultant mezcal. Double distillation tends to create clean, well balanced mezcals, while refrescadors create mezcals which are more vibrant with a touch of salinity. However this is not a set rule; ultimately it depends on the skill and perception of the Maestro Mezcalero.