Belgian Balance Siphon

The Belgian balance siphon is a vacuum brewer with a bit of clockwork theatre. Instead of stacking two chambers like a standard siphon, it puts a metal water kettle and a glass coffee vessel side by side, joined by a tube. A spirit burner heats the kettle, vapour pressure pushes the water across onto the coffee, and as the kettle empties it rises on a balance arm, dropping a cap over the flame. As it cools, the vacuum pulls the coffee back, ready to pour from a tap. Here’s how it works and how to use one.

The short version

• Two vessels side by side: a metal kettle on a balance arm and a glass coffee vessel.
• Heat pushes the water across, then the vacuum pulls the coffee back.
• It puts its own flame out: the rising kettle drops a cap over the burner.
• CoffeeGeek’s ratio: about 8 g of coffee per 100 ml of water.
• The best-documented early design is Louis Gabet’s 1844 balance siphon, from Paris.

How does a balance siphon work?

1. The kettle is heated by a spirit burner. Vapour pressure pushes the hot water up the tube and across into the glass vessel, onto the coffee.
2. As the kettle empties, it gets lighter and rises on the balance arm, against a counterweight.
3. The rising kettle lets the burner cap drop, putting out the flame.
4. The kettle cools, a partial vacuum forms, and the brewed coffee is pulled back through a filter into the kettle.
5. You loosen a stopper to break the vacuum and pour the coffee from the kettle’s tap.

What do you need?

• A balance siphon, with its cloth filter
• Denatured alcohol or bio-ethanol for the spirit burner; not rubbing alcohol, which burns sooty and yellow
• Coffee, a grinder and scales
• Hot water, to shorten the heating time

How much coffee and water should I use?

CoffeeGeek’s balance brewer guide suggests about 8 g of coffee for every 100 ml of water. That’s a little more than for a standard siphon, because some water stays behind in the kettle. Grind medium: too fine and it can clog the filter.

How do you use a balance siphon, step by step?

1. Fit the cloth filter to the end of the tube in the glass vessel, and seal the other end into the kettle.
2. Add the coffee to the glass vessel and hot water to the kettle.
3. Set the burner: push the balance arm down to raise the kettle, open the burner cap, lower the kettle so it holds the cap open, and light the burner.
4. Watch the water cross. When enough has moved over, the kettle rises and the cap drops over the flame.
5. Let it draw back as the kettle cools.
6. Loosen the stopper and pour from the tap.

Using hot water to start saves a lot of waiting: from cold, the heating can take far longer.

Where does the balance siphon come from?

Vacuum brewers appeared in Europe in the 1830s and 1840s. The best-documented early balance design is by Louis Gabet of Paris, who is reported to have patented a balance siphon with a counterweight in 1844. Where the “Belgian” name comes from isn’t clear from the evidence I’ve found, and “Royal” appears to be a brand name used by modern makers. Several makers still produce balance siphons today.

Balance siphon vs other vacuum brewers

	Balance siphon	Siphon	Cona
Layout	Side by side	Stacked	Stacked
Flame control	Automatic, by the balance arm	By hand	By hand, with a snuffer
Filter	Cloth	Cloth, paper or glass rod	Glass rod
Serving	From the kettle’s tap	Pour from the lower chamber	Pour from the lower bowl

How do you clean it?

Let everything cool fully. Empty the grounds from the glass vessel, rinse the glass, kettle and tube, and rinse the cloth filter well.

General guidance only. Balance siphons use an open flame, hot metal and glass under pressure: keep them away from anything flammable, never leave one unattended and follow the maker’s instructions.

Balance siphon vs other methods

• Siphon: the stacked vacuum pot.
• Cona: the British glass vacuum brewer.
• Napier vacuum machine: an early Scottish relative.
• French press: full immersion without the clockwork.

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