Siphon (Vacuum Pot)

The siphon, also called the vacuum pot or syphon, is one of the oldest coffee brewing devices still in active use. Patented in Germany in the 1840s by Loeff of Berlin, it was refined and popularised in France and later in Japan, where it became a defining feature of kissaten cafés. Today it occupies a niche as the most visually dramatic of all brew methods and one of the most temperature-stable.

How It Works

The siphon has two glass chambers connected by a tube with a filter at the lower end. The bottom chamber holds water; the top chamber sits above it. When heat is applied to the bottom, the water heats and produces vapour pressure. This pressure forces the hot water up through the tube and into the top chamber, where it meets the ground coffee and immerses it. The brewer essentially pushes water upward using physics rather than gravity.

When the heat is removed, the bottom chamber cools rapidly, the pressure drops, and a partial vacuum forms. The vacuum pulls the brewed coffee back down through the filter and into the bottom chamber. The grounds remain in the top chamber, held by the filter. The result collects below, ready to serve.

Why Temperature Matters

Most pour-over and immersion methods involve temperature decay: the water is hottest at the start and cools as brewing progresses. In a siphon, the brewing chamber sits over active heat for the entire brew time. The water stays within a very narrow temperature band — typically 88–92°C — throughout contact with the grounds. Extraction is therefore highly consistent from start to finish. Compounds that only extract at specific temperatures are extracted predictably.

This temperature stability is the siphon's primary technical advantage over other methods. The resulting brew often shows exceptional clarity and a very clean, transparent flavour expression.

Parameters

• Grind: Medium. Slightly finer than a V60, coarser than AeroPress concentrate grind. A burr grinder is necessary; blade grinders produce uneven particles that cloud the final brew.
• Ratio: 1:14 to 1:16. Similar to pour-over ratios.
• Brew time: 1:00–1:30 minutes in the upper chamber. Stir gently after water rises to wet all grounds, then stir once more before removing heat to ensure even extraction.
• Temperature: 88–92°C. Lighter roasts benefit from the higher end; medium roasts do well at 88–90°C.

Filters

Three filter types are available:

Cloth filter: Traditional and widely preferred in Japan. Produces excellent clarity while allowing a small amount of oils through. Requires thorough rinsing after each use and must be stored in water in the fridge between sessions. Replace when it begins to impart off-flavours.

Paper filter: Produces the clearest, most transparent brew. Convenient; discard after each use. Slightly flatter texture than cloth.

Metal filter: Most durable but allows fines and oils through freely. The resulting brew is closer to French press in texture. Less popular for siphon, where clarity is often the goal.

Heat Sources

The siphon requires a controllable heat source. Options:

Butane burner: Compact, controllable, the most common choice for café use. Clean flame with no soot.

Halogen lamp: Used in Japanese café siphon bars. Very precise temperature control; no open flame.

Spirit lamp: Traditional, but difficult to control and leaves a slight flame smell.

Induction or electric: Some electric siphon models exist but sacrifice visual drama.

The Kissaten Tradition

In mid-20th-century Japan, the siphon became integral to the kissaten café culture. Baristas prepared each cup individually, often in silence, with meticulous care for each step. The theatrical aspect was not incidental but central: watching water climb and coffee descend through glass was the experience, not just a byproduct. Some of the world's finest siphon service still happens in Tokyo's old-school kissaten, where the same equipment has been used for 30–40 years.

Practical Limitations

The siphon is fragile, slow (a single cup takes 5–8 minutes of active preparation), and requires attentive heat management. It is not a high-volume brewer. The equipment is expensive relative to pour-over setups, and the cloth filter demands maintenance. For home brewers, it rewards patience and produces results that simpler methods cannot match. For cafés, it works as a table-side experience brew or for special single-serve service.