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When you pour an aerated (fizzy) drink such as lemonade or beer into a glass, the froth rises above the liquid level, but usually stops rising when it reaches the rim of the glass, even though you keep pouring and the liquid level continues to rise.

Obviously if you overdo it, the froth does overflow, but generally the froth height seems to be limited by the rim of the glass.


Secondly, when pouring champagne into a glass, it is usually so lively that it easily overflows the glass. The hack is to first pour a dash into each glass, and then go round them again. Now it doesn't overflow so readily.

What is the science behind these behaviours?

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    $\begingroup$ Question does not match title. $\endgroup$
    – DKNguyen
    Jan 9, 2023 at 20:52
  • $\begingroup$ I think it would be better to ask as what is happening when formed bubbles reach the end of any glass, and consider that the bubbles as a group are bound in the surface tension of the fluid (and additional support of the glass to maintain it's volume). Certainly running out of glass means less constraints on the shape. But I don't see how that causes it to stop, if new bubbles form faster than they dissipate then they will just overflow anyways regardless of rim. $\endgroup$
    – Triatticus
    Jan 9, 2023 at 22:02

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Foam is weird. A strange colloidal suspension of liquid and gas that can act as a solid but still has some properties of a liquid ( surface tension, capillary action). While foams can keep their shape, it's not guaranteed and dependent on surface tension, self adhesion, and gas pressure in individual bubbles. Beer foam keeps its shape much better than champagne foam for these reasons.

As a carbonated liquid is poured, foam is created and grows following the shape of the glass. During this process the foam adheres to the glass (partly due to capillary forces) as the foam rises. When the foam reaches the rim the change in capillary/adhesion forces stretch the bubbles until they break at the rim. The popping of these bubbles wet the rim of the glass and eventually, the capillary forces will wick the foam over the rim if the pouring is too aggressive.

I don't have an answer to your champagne pouring strategy except to suggest that the initial pour allows a "softer" follow up pour by replacing a liquid-solid collision with a liquid-liquid collision.

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    $\begingroup$ A nice intro to foams:The Strange Physicsof Foam - NASA Science science.nasa.gov/science-news/science-at-nasa/2003/09jun_foam $\endgroup$ Jan 11, 2023 at 15:56
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    $\begingroup$ Thanks for the NASA link too. $\endgroup$ Jan 11, 2023 at 18:43
  • $\begingroup$ ...from which two things come to mind, a) the behaviour of a foam which is changing state such as cavity wall insulation which sets as it is being injected. b) a possible 'perfect' foam along the lines of a well-designed gravel mixture for making concrete, where the largest stones touch, and their interstices are filled with a smaller size of stone, which just touch, and their interstices ... etc (until the smallest crevices are filled with cement, the glue). $\endgroup$ Jan 11, 2023 at 18:53
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Champagne appears to more carbonated than most other drinks. That would easily why champagne is more "lively". Never heard of any "corking"-type behaviour on other drinks so I would think champagne is more carbonated than most.

Beer = 2 to 4 volumes, or 2 to 6 g/L.

Seltzer = Around 4 volumes, or 6 g/L.

Champagne = Around 6 volumes, or 8 g/L.

https://www.seriouseats.com/cocktail-science-what-is-carbonation-how-to-carbonate-soda-better-carbon-dioxide-facts

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    $\begingroup$ Having experience with overcarbonated beer, there's also something about the rim of the glass that -- for some reason -- causes the bubbles to break as they rise above it. $\endgroup$
    – TimWescott
    Jan 10, 2023 at 0:50
  • $\begingroup$ @TimWescott Capillary action helps cause the foam to rise while in the glass. Once the foam runs out of glass the change in capillary forces causes the bubbles to break at the rim. $\endgroup$ Jan 10, 2023 at 1:13
  • $\begingroup$ @SteveSaban That sounds a bit more relevant than my surface tension thing. If you post that as answer, I will remove the fist half of my answer and only leave the level of carbonation. $\endgroup$
    – DKNguyen
    Jan 10, 2023 at 4:48
  • $\begingroup$ @SteveSaban there is some break-even point in the dynamics. Sometimes the froth is building so fast that it does overflow, even though the liquid itself can be well below the rim. $\endgroup$ Jan 10, 2023 at 9:20
  • $\begingroup$ The question already observes that champagne is more lively than most, so although I upvoted for your time and effort, this does not answer either of my questions. $\endgroup$ Jan 10, 2023 at 20:29

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