A coffee percolator is a type of stove-top brewing device that brews the coffee by continually cycling near boiling point water through the ground coffee beans until the required strength is reached by the brew.
The Percolator is one of the more familiar methods of brewing coffee in the U.S. It works by sending boiling water upwards, through a tube to the top of a perforated basket, where it rains down over the coffee grounds, and back down into the boiling water to start the process repeatedly. Many people still enjoy this old favorite, and with careful timing you can get a wonderful cup.
To “percolate” means to filter through. It also means to become spirited, lively, just like the bubbling you see inside the glass top of non-automatic percolators. The glass top helps you to see the changing color of the brew and determine its readiness for consumption