Floating

• In layered drinks, one or more alcoholic beverages are “floated” on top of others so that each layer is separate, giving the drink a banded appearance. Relative density makes this monochromatic trick possible -- each beverage has its own density, and when left unmixed, the heavier, denser drinks naturally sink to the bottom. More alcoholic beverages are less dense, so when champagne meets the less-alcoholic stout, its relative density causes it to float if left unmixed. To encourage clean layers, pour the second layer over a the back of a spoon so that the beverage gently runs down the side of the glass rather than splashing into the first drink.

Black Velvet

• The cocktail known as black velvet famously floats champagne atop stout. This drink traces its roots to London's Brooks's Club in 1861. On the day of Prince Albert's death, the club steward added stout to the champagne, feeling that even the bubbly wine should be in mourning. To make a black velvet, simple fill half a champagne flute or Tom Collins glass with thick, high-quality stout and then slowly fill the other half with extra-dry champagne, pouring it over the back of a spoon. The result is a drink divided into a nearly black bottom layer with an amber-hued top layer. Over time, the two layers will mix into a deep brown color, or you can simply mix the drinks from the start if you don't want the layered effect.

Variations

• If you substitute hard cider for champagne, the black velvet's rich flavor acquires a more tart edge. This drink is commonly known as a snakebite, or more crassly, a “poor man's black velvet.” Stout also lends itself to the classic black and tan, a layered beer cocktail in which black stout is floated on top of tan ale or lager at a half-and-half ratio.

Champagne on Top

• Black velvet isn't the only cocktail that floats champagne onto a more dense drink. The 1920s sensation known as Buck's fizz features grenadine on the bottom, orange juice in the middle and bubbly on top. While black velvet is smooth and rich, Buck's fizz is tangy and sweet. For a more complex, fruity flavor that layers champagne atop cool bluish-purple hues, try a stormy morning. Fill the bottom half of a highball glass with elderflower liqueur and crème de violette over ice, then add a hearty splash of lime juice, float the champagne on top and garnish with a lime wedge.