The most common technique for floating or layering an ingredient is to pour it slowly over the back of a spoon. This disperses the liquid over a wider surface, allowing it to float instead of sinking under its own weight. As you can see, the technique is simple. The trick is to place the ingredients in layers according to their specific gravity.
This means that the heaviest ingredients are placed on the bottom and each layer builds up so that the lighter liquid is on top. The greater the difference in density between two layers, the more defined the separation will be. Stratification can be achieved in two ways. The first involves pouring liquid through the spiral handle of a bar spoon, keeping the flat disc-shaped end of the spoon on the surface of the drink.
Alternatively, you can hold the end of the bowl of a bar spoon (or soup spoon) in contact with the side of the glass and over the surface of the drink and pour slowly over it. The term “float” refers to placing the final ingredient of a cocktail in layers on its surface. Layered cocktails taste good, look amazing, and impress anyone who sees them successfully serving them. They're usually associated with sweet liqueurs, but many layered cocktail recipes use rum, whiskey, vodka, and other hard liquors to reduce sweetness and add a special touch.
Christmas is a time for overindulging, which is why Christmas cocktails tend to be rich in every sense of the word. As the name suggests, layered beverages include layers of different ingredients, often with contrasting colors. While “pouse” type coffees have largely fallen out of use, waiters are still using the same floating technique. Drink the mix yourself, use it as a single ingredient in another cocktail, put it in a coffee (or other drink), or soak a cake in it for a great dessert (the latter is as simple as it sounds).
This is an extremely artistic approach to serving cocktails, and there's no end to what you can think of. Whether your style is “cin-cin” or “chug chug”, there's a layered cocktail for you. A rainbow in a glass, these beverages included three to eight or more colorful layers of liquors of various flavors at once. Apparently, someone brought out a 34-layer drink.
Pour the heaviest liquor or into a shot glass or a soda glass (or whatever you prefer; the wider the glass, the less visible the layers will be). Floating alcohol or any liquid ingredient isn't difficult and is an excellent waiter technique to learn.