One of the top 10 questions people who end up at this site put into search engines such as Google is a query about how to distinguish between porter and stout, something I’ve not actually tackled head-on yet. So – what difference is there between the two beers?

Er …

None.

Not now, anyway, not in any meaningful way. I’m not sure that there was ever a point, even when porter was at its most debased, when you could point to any truly distinctive difference between porter and stout except to say that “stout” meant a stronger version of porter. Indeed, for much of the past 300 years, to ask “what’s the difference between porter and stout?” would have been like asking “what’s the difference between dogs and Rottweilers?”

Since the revival of porter brewing, or to be more accurate, “the revival of beers being called porter”, even the “different strength” division has vanished, with several brewers making “stouts” that are weaker than their “porters”, I don’t believe it’s at all possible to draw a line and state categorically about dark beers being brewed today: “Everything over here is a stout and everything over there is a porter.” You can’t even draw a couple of meaningful Venn diagram circles and label one stout and the other porter: in terms of strength, ingredients, flavour and appearance, modern-day stouts and porters, I suggest, with the exception of “milk stouts”, occupy effectively identical spaces.

Here’s a quick and dirty survey of 30 more or less randomly chosen porters and stouts from the 2009 Good Beer Guide, 15 of each, with their ABVs and the adjectives used to describe them:

Porters 2009 Brewer ABV Adjectives Elland 6.5% creamy liquorice chocolate roast malt Larkins 5.2% roast bitter-sweet fruity Oulton 5.2% fruity bitter-sweet Cox & Holbrook 5.0% caramel roast malt very sweet White Horse 5.0% dark red chocolate fruity berry Wicked Hathern 4.8% ruby lightly smoked chocolately nutty Beowolf 4.7% mint-chocolate liquorice roast fruit toffee Berrow 4.6% ruby hops Bartrams 4.5% ruby hops Burton Bridge 4.5% malty roast fruit liquorice bitter Enville 4.5% sulphurous sweet fruity Moor 4.5% fruity roast malt slightly sweet RCH 4.5% chocolate coffee roast dark fruits Vale 4.3% roast rich fruitiness sweet to dry hoppy Pilgrim 4.0% roast bitter-sweet berry fruit Average 4.8% Stouts 2009 Brewer ABV Adjectives Outstanding 5.5% bitter liquorice Burton Bridge 5.0% roast malty fruity Famous Railway Tavern 5.0% full-bodied intense roast grain sweet to dry Keynsham 5.0% roast liquorice smoky Wapping 5.0% bitter fruit dry Bartrams 4.8% biscuity smoked lightly roast coffee Beowulf 4.7% charcoal liquorice raisins Wye Valley 4.6% smooth roast bitter B&T 4.5% bitter coffee roast Goachers 4.5% Irish-style Hop Back 4.5% roast sweet malty Titanic 4.5% tobacco smoke liquorice chocolate dry Town House 4.5% roast chocolate toffee sweet to bitter Big Lamp 4.4% roast malty Woodlands 4.4% creamy roast dry Average 4.7%

The porters, you will notice, are on average slightly stronger than the stouts, though if you take the Elland 1872 Porter out, the averages are exactly the same. Commonest adjectives used for porters: roast (60%) fruity (53%) chocolate (33%) sweet (27%) liquorice (20%) ruby (20%). Commonest adjectives used for stouts: roast (67%) liquorice (27%) bitter (27%) dry (27%) fruity (20%) smoked (20%). I’m not certain how meaningful this is – it suggests that porters (in the UK at least) have a tendency to fall on the fruity-chocolate-sweet side, stouts on the liquorice-bitter-dry side, but the differences are not that marked. A survey that chose a different 30 porters and stouts might easily have different results, and there are certainly stouts that are fruity, porters that are dry.

I suspect that when a brewer brews something today he or she calls “stout” this is simply meant to mean that it will be a dark beer, while if it is named “porter”, the beer is very probably meant to be making a nod at an idea of authenticity, a suggestion that it is true to an earlier model. However, since anyone looking for an earlier model of porter has a choice of at least six or seven different versions (roughly 1720s, 1740s, 1780s, 1820s, 1880s, 1910s and 1930s, I would suggest, with each era of porter being significantly different from its predecessor in one or more of ingredients, method of manufacture, flavour and strength), “authentic” is meaningless without being specific about which period you’re trying to be authentic to, and it certainly doesn’t tell you what sort of drink you’re going to get.

Historically, from the 1720s to the early 20th century “stout” (or to be more accurate, brown stout – it is possible to find references to “pale stout” right up to the early 1840s) was just another name for strong porter. There are plenty of references from the early 19th century showing that, for both brewers and drinkers, “strong porter” and “stout” were interchangeable terms: one of my favourites comes from a court case reported in The Times in July 1803, which revolves around the marvellously named crime of “sucking the monkey”.

An attorney called Johnson was suing a carrier called Ottadfield (sic) for the price of a 36-gallon cask “of porter, of superior quality, called Brown Stout”, which he had bought as a present for his mother and had paid to have delivered to her in Barnsley by wagon. The cask arrived safely but on the way north “an accident happened to it, which now and then took place, namely the sucking the monkey.” Someone had inserted a straw or tube into the cask through a hole bored into it with a gimlet and sucked out all the rich and doubtless deliciously alcoholic contents. All that arrived in Barnsley was what The Times called the “caput mortuum”, the empty cask. The beer was described in court as “remarkably fine old porter and very strong” and “excellent brown stout”. Johnson was awarded £5 2s 2d damages for the loss of the porter and the cost of the cask, the carriage and the booking.

Three decades later, in 1831, “stout” still mean “top quality porter”: when the partners at Truman’s brewery in Brick Lane, on the eastern edge of London, one of the three or four biggest porter brewers in Britain (and thus the world) renewed their lease on the premises for 61 years at £1,500 per annum and four kilderkins of “the Best Beer or Porter called Stout”.

As Ron Pattinson has pointed out, notably here, early 19th century brown stouts very often had identical recipes to the same brewer’s porter, differing only in the amount of wort drawn off a given quantity of malt: less water was used for mashing stouts, so that they would be stronger.

Ron has also put together a survey of stout and porter gravities showing that in the 19th century the average beer described as porter had a gravity of a little less than 1058, while stouts were on average about 1078. In the second half of the 19th century, recipes for stout and porter start to diverge: I’m indebted once again to “Statto” Pattinson for the figures: as his tables here and here show, as the strength of the black beer grew, generally speaking London brewers in the later 19th century dropped the proportion of black (or roast) malt and increased the proportion of brown malt, while final gravities in the stronger beers climbed. If I’m interpreting this correctly, the stronger stouts would thus have tended to be less roasty and rather sweeter than the porters – particularly if they were sold “mild”, that is, unaged.

My suspicion is that this was the start of a long move towards English brewers producing sweeter stouts, which was definitely in progress by the 1880s, and which culminated in the arrival of “milk” stout, containing some unfermentable lactose sugars, in the 1900s. In 1883 the Brewer’s Journal made several references to sweet-tasting stouts brewed with a considerable quantity of non-malt saccharine. “one-fifth or even larger proportions of Egyptian sugar… This stout …tastes extremely sweet.” The move to sweet stouts, the Journal said, was “rendered necessary, perhaps, by a desire for rapid turn-over and a changeable public taste.”

These sweet stouts had to be sold quickly, however, or secondary fermentation would destroy their sweetness, The arrival of milk stout around 1908, which would stay sweet without any danger of further fermentation, probably hastened the end of production of the slightly older types of sweet stout. made from 20 per cent and more sugar. (Though as Ron P has shown [thanks again, Big Man], sugar usage rose during the First World War.)

There is no evidence that I’ve been able to find from the literature, however, of any major difference developing between the standard, drier porters and stouts, except that stouts continued to be stronger, Recipes were changing, though: the Journal wrote in February 1890 that brown malt was now

“no longer used by the majority of brewers in the production of black beers to anything like the original extent … [original, here, meaning 20 or 30 years earlier rather than the 1720s] … the brown malt of the present day neither corresponds in physical appearance or value to the “blown” material that was manufactured with the greatest possible care fifteen or twenty years ago. In fact crystal and candied forms of coloured malt have latterly been taking the place of the brown, while dextrinous forms of caramelized sugar are now frequently used …”

By now porter was losing ground to mild as Britain’s (though not Ireland’s) favourite drink, a process hastened by the tax rises and restrictions of the First World War. After the war the strength of stout had dropped to the same level as pre-war porter, around 1055 OG, while porter was down to 1038 or so. As porter sales declined even more, one publication, written in 1934, could say; “Porter is a variety of stout”, and similarly TEB Clarke’s book What’s Yours in 1938 called porter “a lowly brand of draught stout”. In the public’s eye, the roles had been turned upside down, and stout was now the generic, porter merely a sub-type. Soon after, British brewers stopped brewing porter, so that Maurice Gorham in 1949 called it “obsolete … though its name survives on the beer pulls of some unmodernised houses. It was originally to stout as X is to XX [that is, as ordinary mild was to best mild]”

There we are, then – a chase down the centuries, during which we’ve been unable to find any real difference between porter and stout except that stout was originally stronger, something which, as was demonstrated way up there at the top of this post, is now no longer true. Hope that answers your question, Google queryist …