A coffee percolator is a device which is designed to be used in the brewing of coffee. The percolator was actually the original coffee brewing device, although they are not commonly seen these days, having been supplanted by drip coffee makers, French presses, and espresso machines. The flavor of percolator coffee is quite distinctive, and some people consider it an acquired taste; it also takes skill to learn to use a percolator correctly, as it is easy to ruin coffee when using a percolator.
There are several parts to a coffee percolator, contained inside the percolator itself, which looks rather like an urn. Working from the top down, the percolator has a spout which allows people to pour coffee, along with a lid which is typically clear so that people can check on the coffee as it brews. Next is a perforated chamber which is designed to hold coarsely ground coffee. Attached to the chamber is a tube, which runs to the bottom of the percolator, making contact with a chamber which holds water close to a heat source.
To use a coffee percolator, the pot is placed over a source of heat such as a stove or campfire. As the water in the bottom chamber heats, it is forced up the tube, where it spurts out over the grounds, making a very distinctive sound. The hot water percolates or seeps through the coffee grounds, eventually trickling back down into the bottom chamber. When coffee is percolated well, the water never quite reaches the boiling point, and the coffee can be quite strong.
The major danger to a coffee percolator is that it is easy to overextract the beans, creating bitter coffee with an unpleasant flavor and aroma. Overextraction happens as a result of using water which is too hot, or because the coffee is rebrewed, with hot coffee being sent through the beans instead of hot water, removing the volatile aromas of the coffee on the second pass. When a coffee percolator is used right, both of these problems can be avoided.
Several companies make electric coffee percolators with sophisticated controls which are designed to extract the best possible coffee. If you use a percolator on the stovetop or on a fire, however, you will need to watch it carefully to ensure that it brews properly. It may take some experimentation to create the perfect coffee with a percolator, so be patient and plan on having a few aborted tries before you make the coffee of your dreams.