Baltic porter

Porter began in London as a top-fermented beer, and the English porters that went to the Baltic in the late 18th and early 19th century were too. The BJCP writes that the Baltic porter was historically top-fermented, and that many breweries later adapted their recipes for bottom fermentation, like the rest of their beers.

According to beer historian Martyn Cornell, that happened in Poland when brewers began making more and more bottom-fermented beers in the Bavarian and Bohemian style. Dark beers such as porter stayed top-fermented for decades, but in the end a lot of Polish porter became bottom-fermented too.

Today the BJCP writes: generally lager yeast, and if ale yeast is used after all, then fermented cold. The Brewers Association even places the style among the lagers: brewed with lager yeast, fermented cold and lagered, which gives a smooth beer.

It is not entirely black and white: Cornell mentions a brewery that was for a long time the biggest porter brewer in Poland and brewed its porter top-fermented in the English way.

What is right: Baltic porter and imperial stout have the same English roots. London porter brewers exported heavily to the Baltic region in the late 18th century, both to Saint Petersburg and to Danzig (Gdańsk).

What is not right: according to beer historian Martyn Cornell, the Baltic porter does not go back to the heavy imperial stout of the Russian court, but to what was called 'double brown stout' in Great Britain, around 7 to 8% alcohol. A Polish publication from 1867 compares the strength of English porter with that of Munich Salvator or bock beer.

The Baltic porter of its own came about when the import was interrupted: by Napoleon's blockade from 1807 to 1814, and in the Russian-administered part of Poland by an import ban in 1824. After that, brewers in Warsaw began making porter themselves in earnest. A lot of Polish porter later became bottom-fermented.

The BJCP puts it more generally: the style developed in several countries on the Baltic Sea after the import of English porters and stouts was interrupted in the early 19th century. And it is much less roasted and often less strong than an imperial stout.

In the 18th and 19th centuries 'stout' was the name for a stronger porter; the word meant 'strong'. At Whitbread in London, porter and stouts were brewed from exactly the same raw materials in 1844; in 1805 only the double stout differed slightly in the types of malt. The difference lay in the amount of water, and so in the strength.

In the 20th century the roles reversed: around 1934 porter was called 'a variety of stout', a kind of stout, that is. By now the difference in strength has disappeared too. Some brewers make stouts that are lighter than their porters.

The BJCP style guide describes English porter as brown and Irish stout as black, and that helps with tasting. But beer historian Martyn Cornell found no sharp boundary in strength or flavour in a sample of 30 British porters and stouts.