A coffee percolator

(caffettiera in Italian) it is a type of pot used to brew coffee. The name stems from the word "percolate" which means to cause (a solvent) to pass through a permeable substance especially for extracting a soluble constituent ^[1]. In the case of coffee-brewing the solvent is water, the permeable substance is the coffee grounds, and the soluble constituents are the chemical compounds that give coffee its color, taste, and aroma. There are two basic types of percolator:

• One which forces boiling water under pressure through the grounds into a separate chamber; and
• One which continually cycles the boiling brew through the grounds using gravity until the required strength is reached^[2].

Coffee percolators once enjoyed great popularity but were supplanted in the early 1970s by automatic drip coffee makers, and more recently by the French press, as well as a renewed interest in espresso coffee. Percolators often expose the grounds to higher temperatures than other brewing methods, and may recirculate already brewed coffee through the beans. As a result, coffee brewed with a percolator is susceptible to over-extraction^[3]. In addition, percolation may remove some of the volatile compounds in the beans. This results in a pleasant aroma during brewing, but a less flavourful cup^[4]. However, percolator enthusiasts praise the percolator's hotter, more 'robust' coffee, and maintain that the potential pitfalls of this brewing method can be eliminated by careful control of the brewing process^[5].

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