An extra-dark, almost black, top-fermenting brew, made with highly roasted malts. Sweet stout, an English style, is typified by Mackeson, which has only about 3.75 percent alcohol by volume in its domestic market but more than 5 in the Americas. Sweet stout usually contains milk sugars (lactose), and is a soothing restorative. Dry stout, the Irish style, is typified by Guinness, which comes in at around 4 percent in the British Isles, a little more in North America and as much as 8 in tropical countries. Dry stouts sometimes contain roasted unmalted barley. Imperial Stout, originally brewed as a winter warmer, for sale in the Tsarist Russian Empire, is medium dry and distinguished by its great strength: anything from 7 to more than 10.