Coffee Making

Coffee beans must be ground and brewed in order to create a beverage. Grinding the roasted coffee beans is done at a roastery, in a grocery store, or in the home. They are most commonly ground at a roastery then packaged and sold to the consumer, though "whole bean" coffee can be ground at home. Coffee beans may be ground in several ways. A burr mill uses revolving elements to shear the bean, an electric grinder smashes the beans with blunt blades moving at high speed, and a mortar and pestle crushes the beans.

Coffee making machines such as percolators or automatic coffeemakers brew coffee by gravity. In an automatic coffeemaker, hot water drips onto coffee grounds held in a coffee filter made of paper or perforated metal, allowing the water to seep through the ground coffee while absorbing its oils and essences. Gravity causes the liquid to pass into a carafe or pot while the used coffee grounds are retained in the filter.In a percolator, boiling water is forced into a chamber above a filter by pressure created by boiling. The water then passes downwards through the grounds due to gravity, repeating the process until shut off by an internal timer, or, more commonly, a thermostat which turns off the heater when the entire pot reaches a certain temperature. This thermostat also serves to keep the coffee warm (it turns on when the pot cools), but requires the removal of the basket holding the grounds after the initial brewing to avoid additional brewing as the pot reheats.
Coffee making may also involve brewing by steeping in a device such as a French press (also known as a cafetière). Ground coffee and hot water are combined in a coffee press and left to brew for a few minutes. A plunger is then depressed to separate the coffee grounds, which remain at the bottom of the container. Because the coffee grounds are in direct contact with the water, all the coffee oils remain in the beverage, making it stronger and leaving more sediment than in coffee made by an automatic coffee machine.
Coffee Making by using the espresso method forces hot, but not boiling, pressurized water through ground coffee. As a result of brewing under high pressure the espresso beverage is more concentrated and has a more complex physical and chemical constitution. A well prepared espresso has a reddish-brown foam called crema that floats on the surface.