Guinness - the beer whose bubbles sink - the Awesome World of Things
I have personally researched this perplexing phenomena for hours in remote locations like Durty Nelly's and the Gravity Bar.
Scientists, far more clever and pissed than me, have determined that the flow in a glass of stout depends on the shape of the glass. If it narrows downwards, such as in the traditional pint, the flow is directed downwards near the wall and upwards in the interior and sinking bubbles will be observed. If the container widens downwards, the flow is opposite and only rising bubbles will be seen.
It takes precisely 119.5 seconds for a Guinness to settle.
The production of Guinness, involves the use of isinglass made from fish. Isinglass is used as a fining agent for settling out suspended matter in the vat and some minute quantities might be carried over into the beer.
Find out more about the beer over at LinkedIn here?