Grain power

The rise of craft brewing has revived our interest in porter, a dark beer made from brown malt. Despite porter’s presence in Irish literature, lore and legend, it’s an English invention, created by London breweries in the 18th century. The name is thought to have derived from the drink’s adoption as the pint of choice among street and market porters. The histories of porter and stout are intertwined. Stout means strong. Porters were marketed according to strength, under names such as Extra Porter, Double Porter and Stout Porter. Later, the term Stout Porter was shortened to stout.

London porters were hefty brews. In the 1770s, the hydrometer, then a newly invented gadget, transformed the nature of porter. Trials using a hydrometer recorded porter as having an original gravity of 1.071, which translated to an ABV (alcohol by volume) of more than 6.5%. Originally, it was brewed from 100% brown malt. The new device enabled brewers to accurately measure the yield of various malts, revealing that brown malt, while less expensive than pale, produced only two-thirds as much fermentable material. When the malt tax was increased to help pay for the Napoleonic Wars, brewers had an incentive to use less. Their initial solution was to use a proportion of pale malt with added colouring, but a law passed in 1816 restricting the ingredients of beer to just malt and hops scuppered this. The brewers’ dilemma was almost instantly solved by Daniel Wheeler. Wheeler devised a patent malt, capable of colouring a large quantity of wort, making it possible to brew porter from 95% pale malt and 5% patent malt.