Fortunately, vacuum coffee makers are still being manufactured today. And you can still get older versions of vintage vacuum coffee makers on ebay.com. They just have this look about them that is so elegant, so retro and so inviting that once you master vacuum coffee makers, you may never go back. Vacuum coffee makers work on a very simple scientific principle: the expansion and contraction of gas.
The top sphere is where the brewing takes place. A gasket creates a partial vacuum in the lower vessel, drawing the infused water between the two vessels. Underneath the bottom sphere is a heating unit. Vacuum coffee makers can be electric, have an alcohol burner, a special butane burner or be designed for use on a gas or electric stove. Once the unit is set up, all the cool science of vacuum coffee makers takes place. The water in the lower chamber heats up. The water vapor created (think steam) wants to escape. The only route is through the siphon tube, which is blocked by the water. To escape, the vapor pushes the water into the upper chamber where the coffee grounds are waiting. Water continues to be forced up the tube until the vapor can have an escape route. This is a very good thing in vacuum coffee makers. It means that the water in the lower chamber is at the ideal brewing point at 180 to 200 degrees. As such, the oils are released from the ground beans up above. As the vapor arrives, it heats the water in the upper chamber to the perfect drinking temperature is not too hot and not too cold, but just right. Once all the water is in the top and the vapor has done its thing its time to turn off the heat below. More magic occurs. When the heat is removed, vacuum coffee makers reverse the process, pulling the infused water back through the filtered siphon and into the lower chamber.
This process in vacuum coffee makers, known as the kick down, is so efficient that the spent grounds will feel dry to the touch, as if they've been vacuumed dried. Well, they have. Best of all, vacuum coffee makers are very affordable. They are certainly in the same range as drip coffee makers, especially if you get the non-electric variety. If you crave a perfect pot of coffee, try vacuum coffee makers.