We discovered the Coffee vac (or syphon) many years ago when we bought our coffee from a local coffee roaster/seller in Port Melbourne Coffee for Connoisseurs . We fell in love with it and it is still going strong - although I have replaced bits of it over the years! A very brief description is - You start with the coffee grounds in the top section and the water in the bottom. Once it is over the heat and the water rises to the top to mix with the coffee grounds it causes a vacuum in the bottom section. Once taken off of the heat the vacuum causes the brewed coffee to fall back to the bottom section leaving the coffee grinds in the top section. They have been around in one form or other for nearly 100 years but their hey day was in the 30' and 40's. Click here to see what they looked like and here for a little history.