As absinthe is very potent it's not meant to be consumed straight. This is where the absinthe fountain comes into play. An absinthe fountain is basically just a reservoir for storing ice-cold water, which is then dripped slowly through the fountain's spigots (or, for those of us without a fountain, any carafe or pitcher will do) into a measure of straight absinthe.

The water may be poured through a perforated spoon with a sugar cube on top or directly into the spirit ad libitum.

When the cold water hits the translucent absinthe, it releases essential oils that have been dissolved into the spirit, which produces the famous cloudy effect known as a "louche". Once the drink is fully louched, it's ready to be consumed. This generally happens at a ratio of 3-5 parts water to one part absinthe, so the final product is between 10 and 15% ABV. Ideally, no one will turn into a werewolf at this strength.