Many factors contribute to creating the perfect cup of coffee: the quality of the beans, the preparation method, the grind, and even the water.
Water makes up on average 95% of a cup of coffee . This will therefore be considerably influenced by the quality of the water used for its preparation and the temperature at which it extracts the aromatic compounds from the coffee.
Choosing your water - nm
Tap water, full of impurities, that makes you grimace with every sip, isn't exactly going to be a good thing for your brew, or at least, your Celsius coffee won't taste the same. Take our word for it, we've tested it and the difference is striking, to the point where you can't even recognize our coffees!
Conversely, water that's ideal for everyday drinking won't necessarily be the best for your coffee. For example, some popular mineral waters are too rich in certain minerals.
Depending on the geographical location, water has varying flavors and mineral content. It's necessary to have water with a certain mineral content to be able to "carry" the coffee's aromas, but not so much that it overpowers them.
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For the purists
TDS, or "total dissolved solids," is a measure of water hardness, usually expressed in ppm (parts per million). The SCA recommends a TDS level of 150 ppm, with an acceptable range between 75 and 250 ppm. While TDS is a useful measurement, it lacks precision and does not allow for the identification of which minerals are present, or in what proportion.
Three elements are important in the composition of the TDS:
- Calcium helps extract the aromas from coffee; a deficiency will result in a tasteless cup, while an excess can lead to undesirable sensations (earthy, heavy). Calcium, when combined with carbonates in water, forms calcium bicarbonate and causes limescale buildup, so it's important to limit its presence in a coffee machine. We recommend a concentration between 30 and 50 ppm.
- Magnesium plays a significant role in coffee aroma extraction, much like calcium, but with more delicate aromas and a tendency towards greater acidity. We recommend a dosage between 20 and 40 ppm.
- Carbonates help maintain a neutral pH, act as a buffer, and tend to reduce acidity. They are necessary to temper the strong acidity of washed Ethiopian coffee, but too much will make your cup unappealing. The carbonate content is called carbonate hardness. We recommend a concentration between 55 and 75 ppm.
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Solutions - nf
How can we achieve, or at least come close to achieving, these measures? Two solutions are available to you:
- Filtering your tap water is very simple, relatively economical, and above all, more environmentally friendly than collecting plastic bottles. Filtration can be done either with a filter screwed directly onto your automatic machine or with a filter jug (Brita® or other) if you don't have an integrated water reservoir. More radical methods exist, such as reverse osmosis followed by the addition of desired minerals, but these are mainly used by professionals who are most rigorous in this area.
- Using bottled water : while not particularly economical or environmentally responsible, it does allow you to control the composition of your coffee depending on the type of brewing. We recommend it for gentler brewing methods (filter, V60, Chemex, French press, Aeropress). Choose Volvic® for a balanced cup and Mont Blanc® for a cup with high acidity.
In short, you need water with low mineral content, a neutral or near-neutral pH, and the right balance of components to bring out the coffee's full potential without diminishing it. But in an ideal world, it would be possible to adjust your water based on your coffee of the day. And that's where things get really complicated.
Water temperature - nf
Temperature plays a crucial role in the balance of your coffee and its extraction rate, determining whether it will be bitter or acidic, light or full-bodied. 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 develop properly. Even the slightest temperature difference can significantly impact the cup, especially with specialty coffees , which are more sensitive during extraction.
On espresso machines, this water temperature is usually preset or can be adjusted, but if you consume your coffee using gentler methods (filter, V60, Chemex, etc.), you will need to control it precisely if you want to get the best from your coffee.
The recommended average water temperature is 92°C .
This temperature can be adjusted up or down (88-96°C) depending on several parameters:
- The degree of roasting
- The volume in a cup
- The quantity ground
- The density of the coffee variety (fragile or robust)
We provide recommendations and reference values here, but the best thing to do is to experiment, test and understand your tastes and preferences.
Regarding equipment, we understand that not everyone has the budget or the desire to own an electric kettle with a precise temperature display. In that case, you can use a trial-and-error approach: once your water has boiled, wait between 30 and 45 seconds.
But if you want to take the plunge and buy this kind of high-end electric kettle, we advise you to choose one of these three models:
- Timemore Fish Smart : the most accessible.
- Fellow Stagg : the Rolls Royce of gentle methods, with a very narrow gooseneck that allows you great precision in pouring.
- Brewista Artisan: with a slightly less narrow neck than the Fellow, this allows for a higher flow rate, which can have advantages.