A WORLD OF BUBBLES
Equipe Effervescence, Champagne et Applications GSMA - UMR CNRS 7331 Université de Reims Champagne Ardenne UFR Sciences Exactes et Naturelles
The science of effervescence
Champagne has an enchanting effect: Uncorking the bottle, the ritual of pouring champagne into the glass and the seemingly endless stream of bubbles in the glass...Over the centuries, many writers and artists have been inspired by the magic of champagne!
As with all other natural phenomena, science is at the basis of this 'magic'. To gain more in-depth knowledge, we will catch a glimpse of the scientific background of champagne bubbles. Studio Champagne has asked the most renowned scientist and the only specialized researcher in this field, Professor Gérard Liger-Belair, to talk about his work, the science behind the bubbles, based on various physical and chemical processes.
Gérard Liger-Belair has more knowledge about bubbles in champagne than anyone else in the world. In the last 22 years, he has written more than 100 technical papers and he has published numerous books regarding the subject. His most recent book ‘Un monde de bulles’ (2020) is a complete overview of his achievements and of his extensive research work over more than two decades.
Originally, he studied to become a physicist and oceanographer, but he has chosen a different career path.
The research topic of his PhD (2001) was ‘a first approach of the physical processes behind the bubbling phenomena found in Champagne wines’. Since 2007, he has been working as a professor of chemical physics at the University of Reims Champagne-Ardenne, conducting scientific research on the various chemical and physical processes of bubbles in champagne and other carbonated beverages, like beer and cola.
In 2012, he created his own research team with Clara Cilindre, 'L’equipe Effervescence, Champagne et Applications’.
Using ultra-fast cameras, laser spectometry and X-ray photography, Gérard Liger-Belair carefully studies the formation and movements of the bubbles and examines various aspects of the different phases that bubbles go through.
His findings are groundbreaking and the results are widely used by the champagne industry, both for the production and for the consumption of champagne.
We have asked him to share some of the highlights with us.
Emmanuel Goulet
Let's start with quick recap; the second fermentation inside of the bottle is the quintessence of bubbles in champagne.
Liger-Belair: ‘During the second fermentation, which takes place inside of the bottle, the carbon dioxide cannot escape and dissolves in the wine. This is called the 'prise de mousse'. A new equilibrium is then established between the air space and the liquid in the bottle, which determines the final amount of dissolved carbon dioxide.’
Rocket science; uncorking the bottle
A series of images showing the shock wave when uncorking a bottle at 20°C. The interval between two successive images is 83μs. Photo: Équipe Effervervescence/GSMA.
Liger-Belair: ‘When popping a champagne cork, the carbon dioxide (CO2) and water gas mixture, initially under pressure in the bottleneck, freely expands into ambient air and experiences adiabatic cooling[1]. During the initial uncorking phase, the cork is still somewhat blocking the gas mixture. This prevents the ejecting champagne from reaching the speed of sound. However, as the cork opens further, all those gases escape at supersonic speed and there will be a line of normal and oblique shock waves. Those waves then combine with one another to create “shock diamonds,” or patterns of rings that we can usually see in supersonic jet and rocket exhaust plumes, the so-called Mach disks.’
Read the full article.
[1] Adiabatic cooling is the process of reducing heat through a change in air pressure caused by volume expansion.
One million bubbles...and counting
The infrared camera shows that more CO2 escapes when champagne is served in a flute in an upright position, than when the flute is somewhat tiled..
Photo: Équipe Effervervescence/GRESP
The way champagne is being served, has a huge impact on the amount of bubbles present in your glass. ‘If 10cl champagne is poured straight down into a vertical flute, there will be about one million bubbles in a glass. However, serving champagne by tilting the glass a little (like when serving beer), can boost that number by tens of thousands of bubbles’, says Liger-Belair. ‘This technique can create a big difference in the tasting experience, also for example with older champagnes. It is simple, but very effective.’
Read the full article.
To bubble or not to bubble, that is the question
The formation of the bubbles. The line = 100 μm.:
Photos Université de Reims Champagne-Ardenne
Liger Belair explains; ‘In order to generate any bubbles at all, a glass must contain small imperfections, microscopic fibers, for example from a kitchen towel or just coming from the air. The tiny microfiber gas pockets that they contain, act as nucleation sites for the formation of bubbles. Laser engravings inside a glass can also help to nucleate bubbles; a technique that is often applied by glassmakers to help the process along.
As the generation of bubbles from the nucleation sites is continuous, there will be a constant upward ascent, showing as a tiny bead of bubbles, or, as we say in French, ‘a train de bulles’.
Champagne’s high carbonation makes bubbles grow rapidly during their upwards journey towards the surface, so the taller the glass, the bigger the bubbles. Therefore, bubbles tend to be bigger in a flute than for example in a coupe.’
Read the full article.
Bubbles and flower patterns
Photos courtesy of Guillaume Polidori, Philippe Jeandet and Gérard Liger-Belair.
The life of a champagne bubble is short, but has a massive impact. Liger-Belair: ’It comes to an end when the bubble bursts at the liquid surface, but hów it pops depends on how long the wine has been fizzing. Immediately after pouring, sparkling wines form a layer of foam at the surface. The bubbles then collapse in avalanche fashion; the bursting of one bubble induces its neighbors to pop as well.
After a few seconds, the champagne surface loses its foamy head and new formations of six close-packed bubbles will form. Most of the bubble is below the liquid surface, only the bubble cap is visible above it. Unfortunately, these bubble bursts are only visible by using high-speed photography as we do in our lab; we discovered quite unexpectedly that they form a beautiful flower-like structure with the surrounding bubbles. What a visual treat!’
Read the full article.
From coupe to flute to tulip-shaped glass
Foto: Université de Reims Champagne-Ardenne
Nicole Langen Fotografie
Liger-Belair tells us more about choosing the right glass to serve champagne. ‘The amount and the size of bubbles are both extremely important when tasting champagne; if you are sticking your nose into a glass of champagne after pouring it and there is too much carbon dioxide present, it can provoke an unwanted tingling sensation in the nose.
This phenomenon could potentially happen faster with a flute, in which the concentration of CO2 above the liquid is nearly twice as high as in a wider coupe. There is a lesser chance of provoking this sensation if the champagne bottle is well chilled.’
Flutes and wider coupes are no longer considered to be the optimal glasses to taste champagne. Nowadays in Champagne, most of the time, we uses tulip-shaped glasses.
Liger-Belair: ’The spherical shape of these glasses encourages vertical movement and respects the role of the bubbles as they ‘carry’ the aromas to the surface. The glasses also allow the bubbles to burst at the widest point of the ‘tulip’ to free its aromas, providing enough space for aeration and therefore enhancing the tasting experience.’
Read more about flow patterns and champagne glasses.
François-Régis Gaudry
‘By the way, contrary to popular belief, the presence of smaller bubbles in the glass is not necessarily an indicator of superior quality. Above all, it is related to the age of the champagne and the amount of dissolved CO2 in the champagne.’ Liger-Belair says.
As we thank Gérard Liger-Belair for sharing his valuable knowledge and experience, he mentions: ‘I have met so many people who have told me that I have the best job in in the world, as I have built my career around champagne bubbles and as I work in a lab, which is stocked with the best champagnes. However, the champagnes become undrinkable after we have conducted our research. So, at the same time, I think I have thrown more champagne in the sink than anyone else in the world.’