A number of Oaxacan distillers use only one distillation run to make their mezcals, using a still with a refrescadera. Here’s how it works.

When you heat the liquid in a potstill, at about 170°F the alcohol starts turning to steam and rises up into the cap (or “hat”) on top of the still on its way to the tube leading to the condenser. But some of the steam tends to condense in droplets on the inside of the cap and fall back down into the distillate. Because these drops have already been distilled once, their liquid essentially goes through a second distillation when it gets heated back into steam again. This is called rectification, and it increases the percentage of alcohol in the steam.

Standard potstills at Los Danzantes. The cap has been taken off the still in front. The cap and the curved tube leading up from it are where condensation tends to happen, and it’s shapes influences the quality of the mezcal

For single-run distillation, the distiller replaces the normal cap on top of the still with a refrescadera ( or refrescador, “cooler”) cap

Here’s a photo of the inside of the refrescadera cap. In actual use, the open tube coming up from the still is connected to the long tube leading to the condenser. The distiller pours cold water into the refrescadera, which cools the cap and greatly increases the amount of condensation of the steam into droplets (which fall back into the still and get redistilled) inside the cap and thus increases the alcohol content of the steam that is passing through to the condenser.

This is the refrescadera used by Gabino Juárez in Rancho Viejo

And the one at Sergio Juárez’ destilería in Amatengo.