When Arthur Guinness took out the 9,000 year lease on St. James’s Gate Brewery in 1759, he was a brewer of ordinary ales. The company didn’t start making “the black stuff” until nineteen years later. Even then, Guinness stout remained a minority product for about a hundred years, only becoming widely consumed in Ireland in the late 1800s and early 1900s.
Black stout or porter is brewed using roasted barley or malt (germinated barley grains) so I suppose the dark colour is from carbonization of the cereal. But that’s OK. Carbon does you no harm; in fact, it probably absorbs toxins from your body. I’d like to think that it would help to remove the toxic chemicals produced by your body when it metabolises alcohol, but that probably would be optimistic.
Guinness today is a bit different from the original product, in that it’s pressurised with nitrogen as well as the carbon dioxide used in most beers. Nitrogen has the benefit of making the drink less fizzy, and when passed through the fine filter of the special tap it makes very fine bubbles to create the creamy white head. A major technological advance was made in 1989 when the nitrogen-filled “widget” was included in cans to create a “draught” Guinness that could be drunk at home. (The original widget was disc-shaped, with the current “ping-pong ball” design being introduced in 1997.)
I have to confess to being only an amateur Guinness drinker: I’ll just have the occasional pint as the mood takes me. One practice I’ve had is to try out the Guinness in the themed Irish pubs outside Ireland, something which is inherently dubious on a number of grounds. For one thing, I wouldn’t really be able to tell good from bad (well, unless it was really bad); and I know that the whole “Irishness” is inherently fake. Nonetheless, it’s quite satisfying to take a half-hour out in a strange or foreign land and sit in the cool darkness with a pint of the black stuff, and imagine that the rain is shrouding the mountains outside.