Here are some key technical and historical details of the vacuum coffee maker (ca. 1900) as shown in the blueprint and model: * **Invention & Popularity:** While vacuum coffee makers were invented in the 1830s (notably by Loeff in Berlin and Madame Vassieux in Lyons), they reached widespread commercial refinement and popularity around the late 19th and early 20th centuries. * **Operating Principle:** The machine operates on the principle of vapor pressure and vacuum creation. Water in the lower chamber (*Boiling Chamber*) is heated by a spirit lamp (*Burner*), creating steam pressure that forces the expanding hot water up through a siphon tube into the upper globe (*Brewing Chamber*). * **Brewing Process:** Coffee grounds are placed in the upper chamber. Once the water rises, it mixes with the grounds and brews at an ideal temperature just below boiling (around 90–95 °C), preventing scorching. * **Vacuum Draw (Filter Phase):** When the spirit lamp is removed, the air and remaining steam in the lower chamber cool down and contract, creating a partial vacuum. Atmospheric pressure then pushes the brewed coffee back down through a cloth or mesh filter (*Cloth-Mesh Membrane*) into the bottom glass, leaving the spent coffee grounds behind in the upper vessel. * **Materials & Construction:** Units from this era featured hand-blown heat-resistant glass globes supported by an ornate brass, copper, or nickel-plated frame with insulated handles and knurled clamping screws for secure assembly.