Siphon (Vacuum Pot)

The siphon was invented in the 1830s, with the earliest designs attributed to Loeff of Berlin in 1830. The design was refined by Madame Vassieux of Lyon in 1840, who patented a double-globe siphon. The siphon became popular in Europe and the United States in the mid-19th century and was used in many cafes and homes. In the 20th century, the siphon fell out of favor in the West but remained extremely popular in Japan, where it is still a common brewing method in specialty cafes. The siphon experienced a revival in the West in the 2000s with the growth of the specialty coffee movement, and companies like Hario and Yama Glass began producing modern siphon brewers.

Loeff of Berlin (1830), refined by Madame Vassieux of Lyon (1840). Modern versions by Hario, Yama Glass, and others.

A siphon consists of two glass chambers connected by a tube. Water is placed in the lower chamber and coffee grounds in the upper. The lower chamber is heated (by a burner or halogen heater). As the water heats, vapor pressure builds and forces the water up the tube into the upper chamber, where it mixes with the coffee. The mixture is stirred and brewed at a relatively stable temperature (around 90 to 95 degrees Celsius). When heat is removed, the air in the lower chamber cools and contracts, creating a vacuum that draws the brewed coffee back down through a filter (cloth, paper, metal, or glass) into the lower chamber. The grounds remain in the upper chamber.

The siphon offers unique extraction characteristics. The water temperature in the upper chamber is remarkably stable, hovering around 90 to 95 degrees Celsius, as it is governed by the boiling point and vapor pressure equilibrium. This stability ensures consistent extraction. The agitation from the rising water and stirring promotes even contact between water and coffee. The vacuum drawdown provides a gentle, uniform filtration that produces a very clean cup. The full immersion phase (water in contact with coffee) combined with the vacuum filtration creates a cup that is both clean (like pour over) and full-bodied (like French press), a combination unique to the siphon.

Ideal water for the siphon has a TDS of 75 to 150 ppm, general hardness of 50 to 90 ppm, and alkalinity of 30 to 50 ppm. The stable temperature and full immersion extraction work well with moderate hardness. Water with too much hardness can leave scale on the glass and burner. Water temperature in the upper chamber will be approximately 90 to 95 degrees Celsius due to vapor pressure equilibrium, regardless of the heat source intensity.

Water is pushed upward by vapor pressure, then drawn downward by vacuum suction. The flow is not gravity-driven but pressure-driven, creating a unique extraction dynamic. The vacuum drawdown provides even, uniform filtration across the entire coffee bed.

Typical Extraction Yield: 19 to 22%.

Typical Strength (TDS): 1.2 to 1.5% TDS.

• •Using too fine a grind, which clogs the filter and causes slow drawdown and over-extraction
• •Over-heating, which can raise the temperature in the upper chamber too high (though vapor pressure limits this)
• •Insufficient stirring, causing uneven extraction
• •Leaving the coffee in the upper chamber too long, causing over-extraction and bitterness
• •Not pre-wetting the cloth filter, which introduces cloth flavors
• •Using too much heat during drawdown, which can cause continuous boiling and agitation

• •Stir gently but thoroughly when the water first rises to ensure all grounds are wetted
• •Use a cloth filter for the cleanest, most aromatic cup
• •Keep the cloth filter clean and store it in water in the refrigerator between uses
• •Reduce heat once the water has risen to prevent excessive boiling and temperature fluctuation
• •Time the immersion carefully: 60 to 90 seconds for a balanced cup, longer for more body
• •Stir gently just before removing heat to help the drawdown start evenly
• •Use a butane burner for precise temperature control, or a halogen heater for visual appeal

• •The Agate Filter method using a glass rod filter for maximum body and oil retention
• •Splitting the coffee addition: add half when water rises, then the other half 30 seconds later for staged extraction
• •Using a lower water temperature by pre-cooling the upper chamber slightly
• •Stirring technique variations: the 'Hoffmann stir' (gentle circular), the 'Japanese stir' (back and forth)
• •Controlling drawdown speed by adjusting the heat source or tilting the upper chamber slightly

• •The siphon is dangerous due to the burner. Modern siphons use safe butane or halogen heaters with stable bases.
• •Siphon coffee is bitter. When brewed correctly, the siphon produces a remarkably clean, sweet, and aromatic cup.
• •The siphon is only for show. While theatrical, the siphon produces a genuinely unique and high-quality cup due to its stable temperature and vacuum filtration.

Allow the glass to cool before cleaning. Wash both chambers with warm water and mild soap. Cloth filters should be rinsed thoroughly after each use and stored in water in the refrigerator. Replace cloth filters every 2 to 4 weeks with regular use. The tube and filter assembly should be disassembled and cleaned after each use. Glass can be cleaned with a soft brush.

Check the gasket seal between the upper and lower chambers regularly; replace if cracked or worn. Cloth filters should be replaced every 2 to 4 weeks. Butane burners should be refilled as needed. Handle the glass carefully to avoid breakage. Descaling the lower chamber periodically if using hard water.

• •Chapter 1: Brewing Methods
• •Chapter 5: Extraction Science

• •Specialty Coffee Association
• •Hario
• •Ueshima Coffee Academy