Coffee Vacuum Brewers 

Coffee Vacuums work off of air displacement, tiny bubbles that form in the bottom chamber when the water starts coming up to temperature force the water from the lower bulb to the upper bulb, where the water gets mixed with the coffee grounds, steeps a bit, then, when removed from heat, gets drawn back down through the filter into the lower bulb due to the vacuum that gets created when cooled. vacuum. The entire process is fascinating to watch, and provides an excellent cup of brew. The brewed coffee in a vacuum is never directly exposed to heat.