The “Guinness Cascade” is the name given to a phenomenon you can observe if you’re served a draught Guinness in an Irish pub. When you’re served a pint of this famous stout, the gas bubbles seem to sink to the bottom of the glass, creating the impression of a fall, and different layers of brown and white colors in your pint… It’s a pretty cool chemical reaction to see, and contributes to the consumer’s pleasure before sipping his pint… Here’s a little explanation of this phenomenon, known as the “Guinness Cascade”.
A Guinness waterfall – © venge
No, the Guinness Cascade is not an optical illusion as some might think: this reaction is a natural phenomenon, created by the temperature difference between the beer poured and the glass. Guinness is generally served chilled, at a temperature of 6°C, using a special nitrogen-powered filler. Nitrogen generates smaller bubbles than carbon dioxide (used in more conventional fountains), giving Guinness its distinctive fizz.
However, there are a few rules to be observed when using nitrogen. The bartender must fill the pint of Guinness in 2 batches to ensure that it is served correctly.
This step, coupled with the temperature difference between the glass and the beer, would then create a convection current, forcing the gas to rise through a central current, then fall back down to the periphery of the glass, creating this stratification effect.
It is advisable to wait for this effect to subside before drinking Guinness. According to the experts, the beer is better after this slight waiting time (more uniform, with an ideal foam where you can draw a clover without it disappearing).
This phenomenon often leads to amused discussions at the Pub! However, this phenomenon is not confined to Guinness. The Guinness Cascade can indeed be produced with any liquid, but the contrast produced by a beer as black as Guinness and clear bubbles makes the reaction all the more visible. A rather amusing chemical reaction, which is the signature of this exceptional beer!
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