Why Guinness Has a Creamy Head
Guinness gets its creamy head from being carbonated with a blend of nitrogen and carbon dioxide in a ratio of roughly 75 to 25. Nitrogen bubbles are far smaller than CO2 bubbles, which is why the head is thick, smooth and long-lasting.
How does nitrogen differ from carbon dioxide?
Ordinary beers are carbonated with pure carbon dioxide, which dissolves readily in beer and forms large, sharp bubbles, hence the classic bite of a lager. Nitrogen dissolves poorly in liquid, so it creates millions of microscopic bubbles instead. They rise slowly, feel velvety on the tongue, and the head they form resembles whipped cream. The lower proportion of CO2 also means Guinness is less gassy and tastes softer, with lower acidity.
When did Guinness start using nitrogen?
Nitrogenation was developed by the mathematician Michael Ash, who worked at the brewery on an initiative nicknamed the Daft Project. The result was Guinness Draught, launched in 1959 for the brewery's 200th anniversary. It was the world's first nitro beer, and the principle has since been adopted by craft breweries all over the world.
What is the widget?
A can has no tap, so in 1988 Guinness came up with the widget, a plastic ball filled with nitrogen under pressure. When the can is opened the pressure drops, the widget fires nitrogen into the beer and sets off the same cascading effect you get from the tap. The invention won the Queen's Award for Technological Achievement in 1991, and in a 2004 poll the British voted it the best invention of the previous 40 years, beating even the internet.
Why do the bubbles in Guinness sink?
The famous optical illusion has a scientific explanation: the tiny bubbles rise up through the centre of the glass and drag beer downwards along the walls. Because we look at the wall of the glass, we see a cascade of falling foam. The tulip shape of the pint glass helps the effect too.
The best nitro effect, though, comes only from the tap. At Little Island in Frydek-Mistek we pour Guinness properly, in two stages. Come and watch the cascade live at tr. T. G. Masaryka 1129.