Session Imperial Stout Approaches Its Centennial

History by the Glass by | Jan 2018 | Issue #131

Sun new under the nothing. As I keep telling everyone, there are very few genuinely new ideas in brewing, just words arranged in a slightly different order.

London’s Barclay Perkins brewery fascinates me. Which probably isn’t much of a surprise if you know my blog. Among other things, it was the first brewer of Russian Stout, way back in the 18th century when it still went under the name of former owner Thrale.

It was a powerful beer, over 10 percent ABV and aged for a couple of years, leaving time for complexity to develop through the secondary conditioning with Brettanomyces. I was lucky enough to drink its final incarnations, brewed first at Courage in London and finally at John Smith in Yorkshire. Displaced from home, but still Bretted. The 40 or so bottles of the final two vintages from 1992 and 1993 are my fondest beery possessions.

Unusually, the 1970s version was brewed to the same strength as the one from 120 years before. Most British beers were emasculated by two world wars and few retained their full pre-1914 vigor. Barclay Perkins Imperial Russian Stout belonged to that exclusive club, a beer undiminished by time. Then I looked in the London Metropolitan Archives.

The archives have a good set of Barclay Perkins brewing records. There are a few gaps, but the interwar period is complete. That’s where I discovered another version of its Imperial Stout—a much weaker one, a mere shadow of the original.

Slightly disappointed, I looked at it more closely. The full-strength version was still brewed and dubbed IBS ex (Export Imperial Brown Stout), while the weaker version was simply IBS. Compared to the original, it was session strength.

Not that the session version was a thin and watery beer. With a very high percentage of dark malts, it must have punched well over its weight. It contained three roasted grains, brown malt, amber malt, and roast barley. Between them, these three accounted for between 25 and 35 percent of the grist. Which is a lot, even for an Imperial Stout.

Speaking of sessioning Imperial Stout, when last in Manchester, I was delighted to find Marble’s brewery tap had one on cask. I got a funny look from the owner when I had more than one pint. “I’ve never seen anyone session our Imperial Stout before,” she remarked.

All those dark malts had a couple of consequences. They produced less fermentable wort, which explains the poor degree of attenuation. Most 20th century beers, especially ones of relatively modest strength, usually hit at least 70 percent apparent attenuation. They also produced beer that was extremely dark in color. An SRM value of 40 is pretty much midnight in a coalmine. Above 70 is black hole black.

For a relatively weak beer, it’s also very heavily hopped. Running the numbers through brewing software, I come up with around 50 IBU. Couple that with a large proportion of roasted barley and you’ve got a very bitter beer.

WWII looked to have given session IBS a knockout blow. It was discontinued in 1942, when the necessities of war made brewing strong beer impossible. Churchill insisted beer was available, but he didn’t make any promises about its strength.

Just after the war, session IBS pops up again. This time specifically for the Scottish market, at a strength that would even satisfy the most ardent session crusaders, who insist on a 4 percent ABV cutoff. But as things gradually started to pick up for UK brewing after 1950, the need for a weaker version of Imperial Stout evaporated and Barclay Perkins went back to just brewing the full-strength version.

Would there be an interest in Session Imperial Stout today? I have plenty of recipes if anyone wants to have a go at brewing one.