See also: Wheat Wine
Double IPA (7.5-10.0% ABV) should be hoppy, bitter and resinous, a fuller form of IPA in every sense. Emerging from American craft brewers in the mid-1990s, it is not however without historic precedent, some 19th century British IPAs reaching the lower end its spectrum. The oft-quoted hop content of a Double IPA is 60 to 120 IBUs, though above 100 perceived bitterness does not coincide with measured bitterness. The terms Triple IPA and Imperial IPA, which appeared for a time, are falling out of usage, for adding machismo without meaning.
The American take on this classic English style (8.0-12.0% ABV) is significantly different from the original. While the intense malt is still there the layered richness tends to be absent, extra dimensions coming instead from assertive use of floral or resinous hops. Frank bitterness is not uncommon. The conflation of the words barley and wine is deliberate.
American Strong Ale
Hop forward, sometimes aggressively so, but balanced against a firm malty base, this heavy style (6.5-9.0% ABV) is best described as a like any modern American ale, only bigger. It should lack the intensity and depth of Barleywine, have less bitterness and greater balance than Double IPA but be hoppier than the rest.
Footnote: if a single beer can lay claim to being a style, then Xiauyù and its variants, from Italy’s Baladin brewery, an intense barley wine main with three cycles of fermentation, ending virtually free of carbonation and with the character of a fortified wine, can make that claim. As yet, however, the complexity of its creation has meant that it is scarce and has few imitators.