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What are carbonated bubbles?

Bubbles present a fascinating paradox: they are a strictly physical phenomenon, governed by laws of equilibrium and mass transfer, yet we perceive them as something emotional, festive, almost “magical.” In reality, in a glass of sparkling wine or a carbonated beverage, we are observing dissolved carbon dioxide that, when pressure conditions or surface contact change, starts looking for a way out. The initial push follows Henry’s law: at a given temperature, the amount of gas that remains dissolved depends on the pressure of the gas above the liquid. When the pressure drops (by uncorking, pouring, or shaking), CO₂ is no longer “welcome” in solution and tends to escape.

How bubbles form and grow in the glass

Once the liquid is poured, bubbles need a trigger point, a nucleation site, to form. This is why, in a glass, bubbles seem to start from the same spots. In experimental observations of sparkling wines, many of these sites are linked to tubular cellulose microfibers adhering to the glass (e.g., residues from drying): inside their tiny cavities, a micro pocket of air becomes trapped and acts as a stable “seed” for bubble formation. At this stage, an often invisible physical limit comes into play: smaller bubbles tend to collapse because internal pressure increases as radius decreases (Laplace pressure). Only when the bubble nucleus exceeds a critical size can it grow, detach from the nucleation site, and rise.
From that point on, the bubble grows as it ascends, because more CO₂ diffuses from the liquid to the gas-liquid interface: the system is supersaturated and continues to “feed” the bubble along the way. Moreover, its ascent is not a simple “vertical journey”: the bubble pulls along a microstream of liquid and leaves behind a wake, which can help new CO₂ reach it and influence the behavior of the next bubbles—creating visible “paths” or bubble trains that renew at a measurable frequency, observed through high-speed footage of hundreds of nucleation sites. Wine chemistry also plays a role: natural surfactant compounds (proteins, polysaccharides, colloidal components) can alter surface tension and foam stability, making bubbles more persistent or promoting coalescence.
Finally, temperature acts on several levels: it influences the solubility of CO₂ and the speed at which the gas leaves the solution, but also the viscosity of the liquid, and therefore the way bubbles grow and rise. This is why cooler serving temperatures tend to retain dissolved CO₂ longer and extend effervescence, while warmer temperatures often cause faster release and a shorter overall bubble lifespan in the glass.

Producing and enjoying them: techniques and terminology

The success of bubbles is not just aesthetic. When a bubble bursts on the surface, it generates microsprays and aerosols that carry aromatic molecules toward the nose: this is one reason why effervescence alters bouquet perception and makes certain aromas feel more “present” from the very first sip. Added to this is the “tactile” sensory component: the tingling of CO₂, the perceived freshness, and the ability to “cleanse” the palate all result from the interaction between dissolved gas, bubbles, and the mucous membranes.
As for how bubbles are produced, the classic method in wine is to generate CO₂ through fermentation (in bottle or in autoclave), so that the gas, unable to escape, dissolves in the liquid under pressure. The International Organisation of Vine and Wine (OIV) defines sparkling wines as those where CO₂ overpressure is high (at least 3.5 bar at 20 °C, except for small formats), and classifies production methods based on where the second fermentation occurs—in the bottle or in a sealed tank. There is also an “intermediate” category of semi-sparkling or fizzy wines, with lower pressure (typically between 1 and 2.5 bar), less dissolved CO₂, and often less persistent bubbles. The OIV explicitly links these pressure thresholds to CO₂ content in solution. Finally, more generally (and not only in wine), bubbles can also be produced by adding external CO₂, as in carbonated soft drinks: here, the challenge is not to “create bubbles,” but to control their finesse and persistence, since without a favorable microstructure (suitable nucleation sites, surface tension, viscosity, serving temperature), CO₂ may be released too quickly or unevenly.
In this lexicon, using the right words helps us understand what we’re really looking at. “Effervescence” refers to the overall phenomenon; “perlage” describes the continuous trail of bubbles in the glass—the way they rise and renew over time. And the quality of the experience, poetic elements aside, remains tied to measurable parameters: how much CO₂ is present, how much remains dissolved after opening, how fast it escapes, and through which microscopic “pathways” it transforms from invisible gas into that stream of bubbles that, for two centuries, we’ve kept watching as if it were the first time.

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