How does Guiness not foam over like other beers?



A while back my cousin told me that the little ball that’s inside causes it to not foam over but I don’t quite understand how. I don’t quite understand the logic or even connect the dots.

In: Chemistry

The ball inside some beers is a NO2 filled ball that breaks open when the pressure changes in the can, ie you open it. The beer is lightly carbonated or in some cases not carbonated at all and the nitrogen creates the foam. Thus shaking the can does little to nothing in terms of creating more foam.

From cans I don’t know. With regard to taps in a bar, beers leave the tap via carbon dioxide which yields large and less controllable froth and bubbles. Guinness on the other hand uses hydrogen so the bubbles are much smaller and the foam more condensed, it also makes for the much creamier texture. A beer is usually poured in one fell swoop whereas Guinness does a two part pour so it has time to settle before topping it off thusly more control. I’ve “foamed over” many pints of Guinness though on busier nights.

I don’t know if this helps.