Layering is the act of getting one ingredient to sit atop another. This is key for the presentation of many drinks, and hobbyists will argue that certain drinks must be layered to properly "set off" the taste of each layer as you sip the cocktail. However, it is one of the more difficult techniques in bartending.
Layering is density dependent. Any solution has a specific density. Those with higher density sink through those with lighter densities, and the lighter density solutions will tend to remain floating above the high density liquids. Thus the key to knowing how the layers will turn out is by consulting a density chart. If all else fails, experiment and get used to the liqueurs that you most often use.
Submitted By: Chris on 07-13-06 (Definition has not yet been rated)