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1 September 2020

Chemex: filter coffee and design

Let’s get familiar with this technique to brew coffee

The Chemex Coffeemaker is a manual pour-over style glass coffeemaker, invented in 1941 by Peter Schlumbohm, a German doctor living in New York.
Despite its simplicity, it has been defined as “one of the best-designed products of modern times” and it is included in the collection of the
Museum of Modern Art in New York City.
The classic model consists of an hourglass-shaped glass flask with a conical funnel-like neck and a heatproof wooden collar around the neck, held loosely in place by a tied leather thong.
The brewing process is intuitive: coffee is brewed by placing a paper filter into the neck of the flask, then ground coffee is added to the rinsed paper filter.
Hot water (90-96 °C) is then poured through the coffee and filter, depositing brewed coffee into the flask.
Apparently, this technique looks easy, but there are many variables to take into account to ensure a perfect coffee.
Although each coffee has slightly different parameters according to the desired result, we will give you some simple rules for approaching this brewing technique.
Coffee is not the only thing that matters. There are other aspects to be considered: the characteristics of the water and its temperature, the type of filter, the roast and the grind of the coffee.
The water must not simply be odourless, tasteless and collarless. It should have a hardness between 50-175 ppm (parts per million), an alkalinity between 40 – 75 ppm and a pH between 6.5 and 8.
These parameters may seem very strict, but a water too rich in minerals will give an under-extracted coffee; on the other hand with a light water the coffee would be over-extracted.
As for the filter, we recommend using the original non-recycled white paper filters to avoid intrusive aftertaste that could cover the flavour of the coffee.
Fresh roasted coffees are always preferable for filter brewing, because the CO2 excess is easily buffered and you can fully enjoy the coffee aromas.
Depending on the type of coffee, the grind must be medium/fine, between 400 and 800 µ and the coffee must feel like table salt. In principle, the brewing ratio (i.e. the ratio of coffee to water) is 60 g/litre.
Once these parameters are clear, let’s see into the tools that we need: a gooseneck kettle, a thermometer, a scale, a timer, a coffee grinder, a filter, a Chemex coffeemaker and a good coffee.
Constant attention to the amount of coffee used and to the extraction time are essential to get that perfect tasting cup of coffee.
We have chosen to extract our coffee grown in the Nicaraguan finca (farm) Buenos Aires to enhance its elegant sweet and spicy aromas, so all the parameters have been adjusted to this type of coffee.

Brewing instructions

Pour the water into the kettle, heat it to 90° C and insert the Chemex filter in the top of the brewer.
Pour hot water around the inside of the filter. Rinsing the filter helps heating the dripper and also gets rid of any papery taste.
Whirl the Chemex to evenly distribute the heat and finally discard the rinse water.
To prepare two cups of about 250ml each, weigh and grind 30 g of coffee. Put the Chemex on the scale, pour the ground coffee into the filter and check the weight. Tare the scale and start pouring
the water.
This step is called the bloom. Hot water forces the coffee to release trapped gases and CO2.
Slowly pour just enough water over the grounds to wet them evenly (about 60 g).
Begin pouring continuously in a spiralling pattern, gently swirl the Chemex and let it sit until your timer reads 30 seconds.
The release of the CO2 leads to expansion of the coffee bed, bubbling at the
surface, and wonderful aromas for you to enjoy.
Allow the first part of water to drain through the filter and pour the remaining water in two steps: keep on pouring in a spiralling pattern going from the inside to the outside (and vice versa).
The first step ends when our scale reads 300 g (try to avoid pouring directly in the centre or too much from above to keep the coffee bed as compact as possible).
Pour the remaining water, allow all the water to drain through the filter, while gently swirling the Chemex (as already done at the beginning of the first step).

The time to prepare a perfect Chemex is between 3 and 5 minutes.
Finally remove the filter and the ground from the dripper, pour the coffee and enjoy its freshness and its flavours: chocolate shortcrust pastry, chili pepper, hints of chinotto and a pleasant acidity.