A Great piece (by piece) article by Popular Mechanics
THE WATER - Coffee begins as water in the reservoir (15). Ideally, it starts as cold water—not because of thermodynamics, but because of taste: Hot water has likely had some downtime in the tank of a water heater, which means it’s a little old and a little flat. When the coffeemaker is turned on, the water- heating element (11), a copper coil, begins to heat up. Water goes down the rubber drain tube (9) and into the heating element. When it reaches the boiling point of 212 degrees Fahrenheit, boiling action carries it up the glass water- transfer tube (14). At the same time, that causes the water level in the reservoir to fall, and as it falls, a float (13) falls with it. When the float reaches the bottom of the reservoir, it deactivates a switch (12), turning off the heating element.
THE COFFEE - By the time water reaches the top of the transfer tube, it has cooled to the optimal brewing temperature range of 196 to 205 degrees. It flows into the nine-hole outlet arm (3), which aligns with the opening in the brew basket lid (4) so that water drips into the coffee grounds waiting in the brew basket (5). Because it’s boiling action that forces the water into the outlet arm, the water pulses out of the holes—it’s not the continuous stream a pump would create. That allows the coffee time to “bloom” just like it does when you order a pour-over from the barista at your local coffeehouse. The brew basket’s cone shape creates a large surface area at the top for water to infiltrate while keeping wateramong the grounds for longer before it drips out the narrow bottom.
THE CARAFE - Coffee exiting the brew basket lands in the glass carafe (6) waiting below. The carafe lid (2) funnels it through the destratification tube (1), which ensures that new coffee enters the carafe at the bottom. Different com-pounds are extracted from the coffee grounds after different amounts of time in water, so the first coffee that drips out is usually stronger than the last; the destratification tube ensures an even mix. The carafe sits on the hot plate (7), which contains the hot-plate element (8), a sepa-rate heating element that holds the coffee between 175 and 185 degrees. The temperature is chosen with the hot-plate hi/lo switch (10). The hot-ter option is for people who like to put cold cream in their coffee, and the cooler option is for brave souls who take theirs black. —Kevin DupzykBack