The grounds are placed in a small chamber at the top and plain water goes into the bottom. Brewed coffee drains downward into the bottom chamber. The source of heat can be a stove or a built-in resistance coil. Vacuum Coffee Makers also integrate the heating and brewing functions. Coffee grounds are placed in the clear glass vessel on the top.
Water is heated in the bottom component.
Boiling water travels upward in the tube and contacts the grounds, brewing the coffee in the upper chamber. The brewed liquid remains in the top chamber until the vacuum seal between the parts is broken. The bottom chamber holds water and the upper chamber is empty. A small cup filled with coffee grounds separates the two. The machine has other steam taps for frothing milk for cappucino.