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 double brewed coffee varies widely, depending on how it is prepared.

Double brewed coffee which is run through a coffee machine twice can acquire a strange taste. Some coffee machines can be damaged by having coffee in their reservoir, and the heating of the coffee can kill off 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 coffee 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. Double strength 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 sort of double brewed coffee is ideal for iced coffee drinks, as it keeps the drink tasting strong even as the ice melts.

Whatever you do, don't try 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 would-be double brewed coffee 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 to get a confirmation of what, exactly, is under discussion when someone offers you a cup. You should also be aware that the typically higher levels of caffeine in double brewed coffee can be a shock to your body, and you may experience some uncomfortable side effects as a result of a rush of caffeine to your system.