Bead

What is Bead? Bead is the trail of CO2 bubbles rising from the bottom of the glass to the surface in a sparkling wine, and it serves as one of the most immediate visual cues for quality. Connoisseurs read the bead the way they read a wine's color or legs: looking for fine, numerous, persistent bubbles that climb in a steady, vigorous stream. The term sits alongside two close cousins — perlage, borrowed from French and Italian for a pearl-string of tiny bubbles, and mousse, which describes the frothy head and overall effervescence at the top of the wine. Together these terms give tasters a vocabulary for what is happening in the glass from base to crown.

What to Look For in the Glass

A high-quality bead is fine rather than coarse, with bubbles that are small, plentiful, and persistent. When the bubbles are especially delicate, tasters reach for the word creamy; when they form long, narrow strings reminiscent of a necklace, perlage is the more precise term. The continuous vertical column of rising bubbles is sometimes called the cordon, and the longer that cordon endures after pouring, the higher the perceived quality of the wine.

The physics behind what you see is surprisingly delicate. Bubbles do not form on perfectly smooth glass — they need nucleation sites such as microscopic imperfections, a speck of dust, or an intentionally etched point at the base of a flute. From those sites, bubbles begin at roughly 20 micrometers in diameter and expand to about 1 millimeter by the time they reach the surface. Tom Stevenson has estimated that a single bottle of Champagne contains enough dissolved CO2 to produce around 250 million bubbles; Graham Harding's calculation lands closer to 49 million. Either way, there is no shortage of material for the show.

Bead, Pressure, and Production Style

Bead fineness is not just aesthetic — it is a marker of method. Longer aging on the lees after bottle fermentation produces finer bubbles, which is why traditional-method sparkling wines are judged so heavily on the delicacy of their bead. Coarse, short-lived bubbles often suggest a quicker, less refined production path.

Pressure inside the bottle also shapes what you see. Fully sparkling wines carry 5 to 6 atmospheres of pressure (roughly 73 to 88 psi), and EU regulations define sparkling wine as anything in excess of 3 atmospheres. Semi-sparkling frizzante styles sit lower, at 1 to 2.5 atmospheres; the historic Crémant style used around 2 to 3; and Franciacorta Satèn is bottled at 4.5 atmospheres specifically to achieve a softer, silkier bead. It is a useful reminder of how recent this appreciation is: in the early days of Champagne, bubbles were treated as a fault to be eliminated, not the feature drinkers now study so closely.