How to Use a Chemex: Recipe, Grind and Why It Tastes So Clean

Use 30 g of coffee ground medium-coarse and 500 g of water just off the boil. Seat the filter with its thick side against the spout, rinse it well, then bloom with about 70 g of water, pour the rest in stages, and let it drain. The whole brew should finish in roughly three and a half to four and a half minutes, and you will have two clean, bright cups.

The two things that make a Chemex different from other pour-over brewers — its thick paper and its glass-walled shape — are also the two things that cause most Chemex problems.

The recipe

That is 60 g of coffee per litre, the standard filter strength explained in the coffee-to-water ratio guide. Scale it freely: 45 g to 750 g makes three generous cups. Keep the ratio and adjust the grind.

Step by step

1. Fold and seat the filter. Chemex filters come folded into a cone with three layers on one side and one on the other. Put the three-layer side against the spout.
2. Rinse thoroughly. Pour plenty of hot water through the paper to wash out papery flavours and heat the glass. Then pour the rinse water out through the spout, holding the filter in place.
3. Add the coffee and give the Chemex a gentle shake to level the bed. Put it on a scale and tare it.
4. Bloom. Start a timer and pour about 70 g of water, enough to wet all the coffee. Wait about 45 seconds while the gas escapes.
5. Pour in stages. Add water in slow circles, keeping the level roughly constant, to about 300 g by 1:30, then to 500 g by around 2:30. Avoid pouring directly onto the paper.
6. Let it drain. The bed should be flat and the brew finished between about 3:30 and 4:30. Lift out the filter, swirl the carafe and serve.

Why the filter matters so much

Chemex filters are made of bonded paper that is thicker than the standard filters used in drip machines, and they are why a Chemex cup tastes the way it does.

Thick paper traps more of the very fine coffee particles and more of the oils than thin paper does. The result is a cup that is unusually clean and clear, light in body and bright in flavour — the opposite end of the spectrum from a French press, where a metal mesh lets oils and fines through. It also means Chemex coffee is low in cafestol, the compound in coffee oil that raises LDL cholesterol.

The thickness has a cost: it slows the water down. That is why the Chemex needs a coarser grind than a thin-papered cone like the V60. The water takes longer to pass through the bed and the filter, so it spends longer in contact with the coffee; grind too fine on top of that and the brew runs long and over-extracts.

The stall, and how to avoid it

The most common Chemex complaint is a brew that slows to a crawl in the last minute. There are two causes, and they are worth telling apart.

The grind is too fine. Fine particles migrate down and clog the thick paper. The brew tastes bitter and drying. Grind coarser.

The air channel is blocked. As coffee drips into the carafe, the air inside has to escape, and it does so up the groove of the spout. If the single-layer side of a wet filter sits over the spout, it can collapse into that groove and seal it. Then air cannot get out, the flow slows dramatically, and you will sometimes see the filter pressed flat against the glass all the way round.

The thick, three-layer side is stiff enough not to collapse, which is why it belongs at the spout. If the brew stalls anyway, lift the filter slightly away from the spout with a spoon handle to let air through.

Troubleshooting

When the fault is not obvious, the bitter and sour guide explains how to read what the cup is telling you, and the grind size guide explains why a single step on the grinder can change the brew so much.

Chemex or V60?

They are both cone-shaped pour-over brewers, and they make related but distinct cups.

• The Chemex suits brewing for two or more, makes a very clean and delicate cup, and is more forgiving of uneven pouring because the thick filter and deep bed even out the flow. It needs a coarser grind and takes a little longer.
• The V60 suits a single cup, drains faster through thinner paper, and gives you more control — and more ways to get it wrong. Its cup has a little more body.

A chemist's coffee maker

The Chemex was designed and patented in 1941 by Peter Schlumbohm, a German-born chemist who took out more than 300 patents in his career. He drew on laboratory glassware and Bauhaus design, and the result was a single piece of borosilicate glass with a wooden collar fastened with a rawhide tie — a handle that also keeps your hand off the hot glass.

It has been treated as a piece of design almost from the start. The Chemex is in the collection of the Museum of Modern Art in New York, and it turns up in fiction too: in Ian Fleming's 1957 novel From Russia, with Love, James Bond's breakfast coffee is made in one.

The design has barely changed in more than eighty years. It has not needed to.