Pearls, jícara and carrizo: the science behind mezcal's traditional proof test
Pearls (perlas) are the bubbles that form when mezcal is poured from a height through a reed into a jícara. For centuries, master distillers have used them to judge alcohol content without instruments: if the pearls last, the proof is close to target. In 2020, a study published in Scientific Reports confirmed the test has a physical basis.
How is the test done?
- The master distiller draws mezcal into a carrizo (a hollow reed), capping one end with a finger.
- He lets it fall from a height into a jícara, a cup made from the dried fruit of the calabash tree.
- He watches the bubbles on the surface: their size, how many, and how long they last.
This pattern is called the perlado. A ring of fine, long-lasting pearls signals the desired proof.
What science found
An international team including researchers from Brown University and the University of Twente studied why the test works (Rage, Zenit et al., 2020):
- Bubbles last longest when alcohol is around 50–55% by volume. Away from that range, they pop almost instantly.
- The main reason is viscosity: the water-alcohol mix is thickest right around 55%, which slows the draining of the bubble's film.
- Surface tension and the spirit's natural surfactants also help, creating surface forces (the Marangoni effect) that stabilize the bubble.
- The most stable pearls are about 2 mm across.
The study also found that diluting the natural surfactants with a plain water-alcohol mix made pearls last much less, even at the same proof. In other words, the test responds not only to alcohol but to the spirit's makeup.
What about mezcal under 45%?
Many traditional mezcals are bottled at 45–55% precisely because that's where the perlado is most stable (Nogales, CEMMEZ, 2025). In a 40% ABV mezcal like ZUNTE, pearls form but fade sooner, and that's normal: the proof is set for a smoother profile, not for the perlado.
How it applies to ZUNTE
At the palenque in San Luis del Río, the jícara is still part of the craft: it's the traditional way to taste and serve mezcal. The photo of ZUNTE pouring into a jícara on our site shows exactly that test.
FAQ
What are mezcal pearls?
The bubbles that form when mezcal is poured from a height; how long they last indicates the proof.
At what proof do pearls last longest?
Around 50–55% alcohol, according to a study published in Scientific Reports in 2020.
Why does the pearl test work?
Because of the viscosity of the water-alcohol mix, which peaks near 55%, and the spirit's natural surfactants.
Is a mezcal without pearls a bad mezcal?
Not necessarily. Lower-proof mezcal forms pearls that fade sooner.
