Cona Vacuum Brewer

The Cona is a British all-glass vacuum brewer. Like a siphon, it uses heat to push water up from a lower bowl into a funnel of coffee, then a vacuum to draw the brewed coffee back down. What sets it apart is the glass rod filter: a solid glass rod that sits in the funnel’s spout, so there’s no cloth or paper to replace. Cona traces its first patented design back to 1910. Here’s how to use one, following Cona’s own instructions.

The short version

• An all-glass vacuum brewer, with a spirit lamp and stand.
• A glass rod filter: no cloth or paper needed.
• Cona’s ratio: about 50 g of medium or coarse coffee per litre of water.
• Infuse for 2 to 3 minutes, then snuff the lamp to draw the coffee down.
• Size D holds up to 1.1 litres, good for 4–8 cups.

How does a Cona work?

The Cona works on the same principle as every vacuum brewer:

1. Heat from the spirit lamp builds vapour pressure in the sealed lower bowl, pushing the water up into the funnel.
2. The coffee infuses in the funnel for a couple of minutes.
3. Snuff the flame, the bowl cools, and the vacuum draws the coffee back down, past the glass rod filter, which holds the grounds back.

The glass rod rests in the funnel’s spout by its own weight. Cona dates the introduction of its glass filter to 1947.

How much coffee should I use?

Cona’s own instructions say about 50 g of medium or coarse coffee per litre of water, roughly 1 oz per pint. For a Size D filled to its 1.1 litres, that works out at about 55 g.

How do you use a Cona, step by step?

These steps follow Cona’s user instructions:

1. Fill the spirit lamp with denatured alcohol or bio-ethanol, to no more than 1 cm below the neck, and let the wick soak.
2. Fill the lower bowl with hot or boiling water, to within 1 cm of the base of the neck. Dry the outside and seat it in the stand.
3. Put the funnel in its holder, place the glass filter rod in the centre and add the coffee.
4. Light the lamp. When the water starts to boil, put the funnel into the bowl with a slight twist.
5. Let it infuse for 2 to 3 minutes.
6. Put the extinguisher cap on the lamp. The coffee is drawn back down.
7. Remove the funnel and pour.

Brew mode on this page times the infusion for you.

What sizes are there?

	Size C	Size D
Capacity	About 1.5 pints (Remodelista)	Up to 1.1 litres (Cona)
Serves	Fewer cups	4–8 cups (Cona)

Cona’s current range includes the Size D “Genius” all-glass model.

A short history of the Cona

• 1910: Cona says its first patented design, by Albert Cohn, was a laboratory-style “extraction column”.
• 1947: Cona dates its glass rod filter to this year.
• 1950s: the Aberdeen Art Gallery and Museums collection holds a Cona Model Rex, an electric version with a heating element in the base, dated 1950–1959.
• 1962: Cona says production of the modern Cona design began, and it became a design classic. Its redesign is credited to the graphic designer Abram Games; sources disagree on the exact year.

Cona vs other vacuum brewers

	Cona	Siphon	Balance siphon
Filter	Glass rod	Cloth, paper or glass rod	Cloth
Layout	Stacked, all glass	Stacked	Side by side
Flame	Snuffed by hand with a cap	By hand	Automatic

How do you clean a Cona?

Let everything cool. Empty the grounds from the funnel, rinse the funnel, glass rod and bowl, and dry them.

General guidance only. The Cona uses an open flame and hot glass under pressure: keep it away from anything flammable, never leave it unattended and follow Cona’s instructions.

Cona vs other methods

• Siphon: the general vacuum pot.
• Belgian balance siphon: side by side, with an automatic flame cut-off.
• Chemex: another glass classic, as a pour-over.
• French press: full immersion, with a heavier cup.

Explore every vacuum brewer in the vacuum chapter.