The sometimes-overlooked truth about beer styles is this: They’re always in motion. Fashions change, technology evolves, wars strike, and those styles that survive always end up transforming in the process. There may be no better example than the Irish stout, a 4 percent ABV session beer now engineered to be drunk in threes and fours down at the pub.
This stout is marked by a silkiness that comes from the special nitrogenated dispense system invented for it and has a classically roasty character. But start traveling backward in time, and this ubiquitous beer—the only style besides pale lager found everywhere (usually in Irish pubs)—becomes by increments more and more unrecognizable.
A Porter by any Other Name
The original Irish stouts came from London about 300 years ago, and they were called porter. Their hallmark character came from a particular ingredient known as brown malt—the lowest, roughest grade. It was kilned in such a way that sudden heat caused it to explode like popcorn, and that gave it a burned, acrid flavor—a “smoaky tang” as William Ellis described it in 1736. Brewers hadn’t yet invented sparging and instead drew off successive worts (or “gyles”) from the mash. In other styles, brewers would blend these to produce beers of different strengths; for those early porters, all the gyles were blended back into one “entire” beer.
Porter was destined to become famous, the first global style to set passions ablaze as far from London as Sydney and Philadelphia. Were the beer to be served as brewed, however, porter might not have lasted a year, much less three centuries. Instead, brewers socked that acrid stew away in oaken vats, and there a magical transformation happened. They didn’t know it at the time, but wild yeast slowly nibbled at those smoky bits and what emerged from the vats months or years later was the sophisticated, tart, sherry-like beer that soon became renowned across the globe. Those microorganisms in the wood gobbled up the harsh flavors and replaced them with esters and acids as fine, some said, as French wine.
London porter soon traveled to Ireland and was replicated there without much change until an important event in 1817. That year, Daniel Wheeler invented a roaster that could produce very dark bitter roasts without the smoky tang. He patented his invention, and brewers will recognize the result, “black patent” malt, even today. London breweries took little notice of the event and continued to make their brown-malt porters. Irish brewers, however, embraced the new malt. It created a different flavor profile scorned by one Londoner in 1851 as “soda-water briskness.” The lineage of porters had diverged.
The next evolution came decades later, following a change in U.K. tax law in 1880. (Ireland was, recall, part of the United Kingdom then.) Formerly, only malt could be used in the grists of beer. The Free Mash Tun act of 1880 allowed the use of sugars and an obscure ingredient that would come to characterize Irish stouts—unmalted roasted barley. This was a further deviation from English stouts—as they were by this time being called—which were being made with oddball ingredients such as lactose, oysters, oatmeal, and sugar.
One thing didn’t change through the decades—vat-aging. Despite the changes to the grist, the practice of aging beer for months or years in wooden vats was still very much a mandatory practice. If you’ve ever visited the Guinness Brewery in Dublin, you will have passed by rows and rows of gabled brick warehouses—from the rooftop bar you can see them stretch for blocks. These were filled with vats, thousands of them, and until the 1950s, every bottle and pint of Guinness spent time in one.
The final and dramatic change was the introduction of nitrogenation—which led to the end of vat-aged stout. Indeed, it was intended to end vat-aged stout. Pioneered by the mathematician Michael Ash at Guinness, nitro was designed to replace a finicky, convoluted draft system that combined mature, still vat-aged beer with fresh, highly carbonated beer. The publican would blend them in the pint glass, a process that could take up to a minute to complete. Ash wanted to replicate some of the qualities that system produced while streamlining it, but this may have been the biggest single change in the centuries-long evolution of this beer.
In 1800, Irish stout was a strong, acidic, vat-aged brown beer made with smoky malt. In time, it became a darker, bitterer, strong, vat-aged beer and eventually achieved additional mouthfeel and character through the use of roasted barley. Finally, by the end of the twentieth century, it turned into a session stout, not vat-aged, not strong, darkened entirely by roast barley, and served on nitrogen. We can most easily chart this change through the history of Guinness because it survived all this time, but there were many examples throughout the centuries, including two extant brands from Cork: Beamish and Murphy’s.
The beer we know today has become one of the most rigid styles in the world, little changed since the introduction of nitrogen 60 years ago. It’s so well established that now new-generation craft brewers are making it according to now-fixed standards. When I asked The Porterhouse Brewing Company (Dublin, Ireland) Head Brewer Peter Mosley to describe his approach to Irish stout, he offered tasting notes true of any brand made today.
“A true Irish stout should have a strong dark color, black at first glance, though a deep ruby would be more correct on closer examination. Stouts should also have a rich, full-bodied mouthfeel, traditionally from the roast barley. In an ideal world, the head should also be creamy white and contribute to the sensation of a full-bodied beer.” If you order a pint of stout in Ireland today, this is what you’ll receive. But despite the recent constancy of this beer and its legendary association with Irish drinkers, even Irish stout isn’t fixed. Once it was something more like Rodenbach than draft Guinness. In 20 years? We’ll have to check back and see.