The sake was literally pressed (separating liquid from the mash) by vacuum pressure. This is an unconventional method of pressing the sake that is not commonly used in Japan. In order to extract the sake out of the thick rice mash, the mash is sealed in an air pressurized tank and the sake is literally sucked out of the tank. Most commercially available sake are made by pressing method that totally crushes the rice mash to draw out high yield of sake, but crushing the mash too much can draw out off-flavors or harshness. Thus, Nova decided to create a vacuum of space in the tank to put enough pressure to extract the sake but not enough pressure to crush the rice mash. Result is less yield but clean and refined sake.