The proper term is a Vacuum Brewer. I know the owners at BC Gelati and I really must ask them why they chose to call their vacuum brewers "alembic" which is a word for a laboratory distillation process. Perhaps its what Italians call them. They carried the Hellem models from France, who have since stopped manufacturing them. 'Vac Pots' were invented in late 1830’s europe, and the concept/design is exactly the same today. throughout the 1930’s, 40’s and 50’s, they were mass manufactured (by Solex, Westinghouse, GE etc) and became a very common household and restaurant item. this is long before percolator and filter auto drip machines fully entered the market, which through convenience and marketing (not quality) killed off the vacuum pot. Vacuum brewers are still around, very popular in asia and amongst coffeegeeks who widely agree that the vacuum pot is the finest methods of brewing non-espresso coffee. how do they work? water is heated in the lower chamber and ground coffee is placed in the upper chamber. when the correct brewing temperature is reached, vapor pressure will move water into the upper globe and saturate the coffee. when heat is removed, a vacuum is formed which siphons the coffee down through a cloth filter. when complete the upper chamber is removed and the lower pot is used to serve the coffee. why is it so good? firstly temperature, which is a big problem with almost every other brewing device. pretty much ALL home drip machines do not heat water hot enough to brew coffee correctly. by nature the vacuum pot will only begin to brew when water reaches 195-200 degrees. coffee grinds are being fully saturated, and are being filtered out through cloth or paper when you remove it from the heat. it seems complicated to read (and explain), but its quite a simple device. it looks fantastic, and can be used right on a dinner table in front of guests. read more in the Vac Pot FAQ by Mark Prince. We use and sell the Yama and Hario Vac Pots in our store and I use one at home on a daily basis. Love it.
