Many factors contribute to creating the perfect cup of coffee: the quality of the beans, the brewing method, the grind, and even the water.
Water makes up an average of 95% of a cup of coffee. Consequently, the cup will be significantly influenced by the quality of the water used for its preparation and the temperature at which it extracts the coffee's aromatic compounds.
Choice of water - n.
Tap water loaded with impurities that makes you wince with every sip won't exactly be an asset to your beverage, or at the very least, your Celsius coffee won't have the same flavor. Take our word for it, we’ve run the tests and the difference is striking, to the point of not even recognizing our own coffees!
Conversely, water that is ideal for daily consumption isn't necessarily the best for your coffee. For example, some mineral waters popular with the general public are too rich in certain minerals.
Depending on geographical location, water tastes different and contains varying levels of minerals. It is necessary to have water that contains some minerals to be able to "carry" the coffee's aromas, but not too many, so as not to mask them.
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For the purists
TDS, or "total dissolved solids," corresponds to the measurement of water hardness, generally expressed in ppm (parts per million). The SCA recommends water at 150ppm, with an acceptable range between 75 and 250ppm. While TDS is useful to measure, it lacks precision and does not identify which minerals are present or in what proportions.
Three elements are important in the composition of TDS:
- Calcium: helps extract coffee aromas; your cup will be insipid if there is a lack, and conversely, it may develop undesirable sensations in case of excess (earthy, heavy sensation). Calcium, when combined with carbonates in the water, becomes calcium bicarbonate and will form limescale, which should therefore be limited in a coffee machine. We recommend a dosage between 30 and 50 ppm.
- Magnesium: contributes very significantly to the extraction of coffee aromas like calcium, but with more delicate aromas that tend toward greater acidity. We recommend a dosage between 20 and 40 ppm.
- Carbonates: help maintain a neutral pH, act as a buffer, and tend to decrease acidity. They are necessary to temper the sharp acidity of an Ethiopian washed coffee, but will make your cup uninteresting in excess. The carbonate content is called carbonate hardness. We recommend a dosage between 30 and 75 ppm.
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Solutions - n.
How can you achieve, or at least come close to these measurements? Two solutions are available to you:
- Filter your tap water: very simple, relatively economical, and above all, more ecological than collecting plastic bottles. Filtration can be done either via a filter screwed directly onto your automatic machine or a filter carafe (Brita® or other) if you don't have a built-in water tank. More radical methods exist, such as reverse osmosis followed by the addition of the desired minerals, but these are mainly used by the most rigorous professionals on the subject.
- Use bottled water: not particularly economical or environmentally responsible, but it does have the merit of allowing you to control the composition according to the type of coffee. We recommend it for slow coffee methods (filter, V60, Chemex, French press, AeroPress). Choose Volvic® for a balanced cup and Mont Blanc® for a cup with high acidity.
In summary, you need water that is low in minerals, has a neutral pH or close to it, and has just the right level of components to bring out the coffee's potential without muting it. But in an ideal world, it would be possible to adjust your water according to your coffee of the day. And that is where you become impossible to be around.
Water temperature - n.
Temperature plays a crucial role in the balance of your coffee and its extraction rate, which will result in a coffee that is either more bitter or more acidic, lighter, or conversely, with more body. If the water is too hot, I burn my coffee and its aromatic components, while if the water is too cold, the aromas won't be able to develop properly. And the slightest degree can count and significantly impact the cup, especially with specialty coffees, which are more sensitive during extraction.
On espresso machines, this water temperature is generally pre-set or adjustable, but if you drink your coffee using slow methods (filter, V60, Chemex, etc.), you will need to control it precisely if you want to get the best out of your coffee.
The average recommended water temperature is 92°C.
This temperature can be adjusted up or down (88-96°C) depending on several parameters:
- The degree of roast
- The cup volume
- The amount of ground coffee
- The density of the coffee variety (fragile or robust)
We are giving you recommendations and reference values here, but the best thing to do remains to experiment, test, and understand your own tastes and preferences.
As for equipment, we easily understand that not everyone has the budget or the desire to clutter themselves with an electric kettle with a precise temperature display. If necessary, you have the option to play it by ear: when your water is brought to a boil, wait between 30 and 45 seconds.
But if you want to take the plunge and buy this type of high-end electric kettle, we advise you to look at one of these three models:
- Timemore Fish Smart: the most accessible.
- Fellow Stagg: the Rolls Royce of slow coffee methods, with a very narrow gooseneck that allows for great precision in pouring.
- Brewista Artisan: with a slightly less narrow neck than the Fellow, it allows for a faster flow rate, which can have its advantages.