The first vacuum coffee maker made out of Pyrex, a heat-resistant glass created by Corning, was the Silex. Though vacuum coffee makers had been in use since 1830, ordinary glass made them unreliable and prone to explosion. The invention of Pyrex ushered in a renaissance in vacuum coffee makers. As of 2010, many coffee purists believe that the vacuum process produces the richest and best-tasting coffee through use of vapors and self-filtration.
Pour the desired amount of water into the lower bowl. Fill the bowl 2 in. below the neck for a full pot of coffee.
Place the coffee into the upper bowl. For regular-strength coffee, measure one level tbsp. of coarsely ground coffee for each cup of water.
Place the lower bowl over the oven burner. Connect the upper bowl to the top of the lower bowl, twisting slightly to lock it into place.
Wait six to eight minutes for the water to rise up through the filter and mix with the coffee grounds. Turn off the stove when the water stops rising into the upper bowl.
Wait two minutes for the coffee to filter back into the lower bowl and for the upper bowl to cool. Carefully remove the upper bowl. Pour the coffee from the lower bowl using the handle.