The term “double brewed coffee” is used to describe two different preparations of coffee. In both instances, the end goal is to make the coffee much stronger, concentrating it to create a powerful kick. One technique involves running already brewed coffee back through a coffee maker over fresh grounds, while the other simply requires using twice the normal amount of grounds. The flavor of the coffee varies widely, depending on how it is prepared.
Coffee that is run through a coffee machine twice can acquire a strange taste. Some machines can be damaged by having coffee instead of pure water in their reservoir, and reheating the beverage can destroy some of the flavor, creating a strange, bitter aftertaste. While this coffee is certainly stronger, it is not always very tasty. When old coffee is used, such as that which has been sitting overnight, the result can be rather stale.
More commonly, people really mean “double strength coffee” when they talk about double brewed coffee. Double strength coffee is made with twice as many coffee grounds as usual, creating a very strong, bold flavor. This type of coffee is easy to make in a coffee maker, and it can also be produced in a French press or on the stovetop. Some people also like to throw spices like cardamom into the grounds to make the resulting coffee more interesting. This coffee is ideal for iced coffee drinks, as it keeps the drink strong even as the ice melts.
Coffee experts do not recommend trying to make double brewed coffee by cooking coffee grounds on the stove for an extended period of time. The longer coffee brews, the more bitter it gets, as the heat brings out the tannins in the coffee. The subtle flavors of the coffee will also start to disappear in the heat, leaving the beverage tasting extremely bitter and unpleasant. It is also not advisable to reuse coffee grounds for much the same reason, as the bulk of the flavor has already been leached from them.
Because people can mean two different things when they talk about double brewed coffee, it doesn't hurt for a drinker to get a confirmation of what, exactly, is under discussion when someone offers him or her a cup. People should also be aware that the typically higher levels of caffeine in this coffee can be a shock to the body, and individuals may experience some uncomfortable side effects as a result of a rush of caffeine to the system.