快猫短视频

When beer is poured into a 500-millilitre glass, somewhere between 200,000 and 2 million bubbles rise to the surface to form the foamy head.

This estimate was made by Ge虂rard Liger-Belair and Clara Cilindre at the University of Reims Champagne-Ardenne in France, who calculated the number of tiny bubbles that form before a lager goes flat.

The researchers first measured the amount of carbon dioxide dissolved in 250 millilitres of lager after it was poured into a tilted glass. They then calculated the number of bubbles that would form, assuming the lager was at 6掳C 鈥� its recommended drinking temperature.

The total number is dependent on the type of glass that is used. Bubbles are more likely to form where microscopic crevices and cavities in the inside wall of the glass are more than 1.4 micrometres wide. The researchers included estimates for glasses with different sizes of microscopic crevices 鈥� between 1 micrometre and 10 micrometres in size 鈥� resulting in the large range of total possible bubbles in a glass of beer.

鈥淚f your glass is perfectly smooth on the inside, thermodynamically speaking, it will not be able to produce any bubbles,鈥� says Liger-Belair. 鈥淭he size and amount of these bubbles is dependent on these tiny imperfections in the glass.鈥� The more imperfections on the surface of the glass, the more bubbles form.

The number and size of the bubbles is also dependent on the height of the glass 鈥� taller glasses form larger bubbles. 鈥淭his is because the bubbles grow in size as they rise to the liquid鈥檚 surface,鈥� says Liger-Belair. That is why beer is often poured into a tilted glass: creating a smaller distance for bubbles to travel leads to less foam.

Liger-Belair and Cilindre鈥檚 previous research found that a typical bubble in beer is about half a millimetre in diameter once it reaches the head. For comparison, bubbles in champagne are typically about 1 millimetre wide. But when they first form, beer bubbles can be around 10 micrometres in diameter, says Javier Rodr铆guez Rodr铆guez at University Carlos III of Madrid in Spain, who wasn鈥檛 involved in the research.