What is Sweet Vermouth?

Sweet vermouth — rosso, or Italian vermouth — is wine fortified with distilled spirit, aromatized with botanicals (wormwood historically among them, plus cinchona, citrus peel, spices, and bitter roots), then sweetened. Alcohol and sugar raise stability relative to table wine, but the product remains a wine: once opened, dissolved oxygen continues to work, so refrigeration slows but does not stop decline. Typical bottling strength is about 15–18% ABV.

It is a structural ingredient, not a mixer. In the Manhattan it supplies sweetness, wine acidity, and herbal depth against whiskey and bitters; in the Negroni it is one equal part with gin and Campari. An oxidized bottle will dominate either drink more than a change of whiskey will.

Dried fruit, vanilla, cola spice, bitter herbs, and residual grape. Carpano Antica Formula leans vanilla and cocoa; Cocchi Vermouth di Torino is brighter and more wine-forward; Martini & Rossi Rosso is lighter and useful in highballs. Oxidation produces nutty, bruised-apple, and cardboard notes as aldehydes accumulate after the bottle is opened.

The commercial style crystallized in Turin in the late 18th and 19th centuries, when fortified, wormwood-scented wines moved from medicinal bitters into aperitivo culture. Italian rosso became the default sweet vermouth of the American bar.

The Manhattan (whiskey, sweet vermouth, aromatic bitters), documented in the late 19th century, and the Negroni (gin, Campari, sweet vermouth), a 20th-century equal-parts descendant of the Americano, made the category architecturally necessary. The Americano itself is the same vermouth-and-Campari pairing lengthened with soda.

Refrigerate after opening. A 375 ml bottle is practical if turnover is slow; date the cork or cap. Use within roughly a month for stirred drinks where vermouth is a large fraction of the volume; oxidized vermouth is more tolerable in a highball with soda, where carbonation and dilution mask stale notes.

Standard templates: Manhattan (about 2 oz whiskey, 1 oz sweet vermouth, bitters); Negroni (equal parts gin, Campari, vermouth). If the nose is of stale wine and nuts rather than spice and grape, replace the bottle.