Water makes up more than 98% of a black brew, and around 90% of an espresso, so the water chosen makes a huge difference to all aspects of the final character of the brew. Not only this, but the balance and level of the water’s mineral content makes a huge difference to what we are able to extract from coffee. Dissolved minerals in water exist as charged ions, which help us to bind to the flavour compounds in coffee that lead to the most exciting and involving cups. For coffee brewing, we can think of these minerals existing in two broad categories, General Hardness (GH) and Carbonate Hardness (KH). For natural water hardness, the two most important GH ions are Magnesium and Calcium. Magnesium has a very strong attraction to natural acid molecules, so has a huge effect on perceived acidity in coffee, pulling out flavours we like to describe as fruits in coffee, normally sharper acidities like citrus and forest berries. Calcium has a slightly weaker interaction, so tends to enhance softer acidities like strawberry and cherry, while also directly enhancing body. The final piece in the puzzle is KH, which has a slightly more complicated interaction. Through a phenomenon known as buffering, the carbonate hardness tries to keep the pH (the scientific measurement of acidity) of the water around 7, which is neutral. This means that controlling KH is very important. Too little, and the coffee tastes unbalanced and sharply acidic, no matter what brewing parameters are changed. Too much, and it is impossible to perceive any acidity in the coffee, leaving a flat and dull cup.
Therefore finding the right brewing water is possibly even more important than the brewing method. We recommend using mineral water of a soft Total Dissolved Solids count, ideally below 150 ppm, or asking your local speciality coffee bar if they can provide you with some of their filtered water. For our customers in Aarhus, we are always happy to provide this at either of our locations. You can also create brewing water from scratch, and there are great guides on how to do this at Grind Science and Barista Hustle. (Keep links from before)
There are great guides and recommended mineral contents on the links below.Barista Hustle Grind Scene
To brew coffee well, extraction is an important concept to understand. If we were able to dry out coffee grounds after they have been brewed, they will have lost about 20% of their weight. This is the amount that we have dissolved into our cup during brewing, and the percentage is termed extraction. This is important, as flavour does not extract from coffee in a linear way, more is not necessarily more. When we begin to brew a coffee, the natural acids present in the coffee will extract most easily, followed by sugars, and then heavier bitter compounds towards the end of the brew. This means controlling how much we extract from a coffee will control the balance of flavour in your cup. Extract too little, and we have a sour coffee, too much acid from the beginning of the brew, and not enough sweetness to create balance. Extract too much, and we will extract too much bitterness from later in the brew, resulting in an overall bitter and drying cup.
There are two main ways we can control extraction, in ANY method of brewing coffee. Grind Size, and Contact Time. The table below shows a guide to controlling extraction when brewing.
|Coffee Tastes||Too Bitter/Dry||Too Sour|
By tweaking these variables, and tasting every cup you brew with a critical pallet, you’re sure to be brewing transparent and delicious brews.Brew Guides
This method involves pouring hot water over fresh coffee grounds to extract flavour. Popular methods include V60, Chemex and Kalita Wave. Here as a starting point we would suggest a ratio of approximately 65 g of dry coffee per litre of water, scaled up or down depending on how much you’re brewing, and aim for a brew time of around 3 minutes, either by using a fine grind to slow the flow through the coffee bed, or by spacing out your pours to increase the total contact time.
Here, hot water and coffee sit together in a chamber for a certain period before being separated, possibly by a filter. Popular methods here are the French Press, Aeropress, and cupping. Here we would recommend a slightly higher starting ratio of approximately 75 g of dry coffee per litre of water. Here you are in control of both contact time and grind size, so either start with a finer grind and a shorter contact time of approximately 1 minute, popular with Aeropress, or a coarser grind and a longer contact time, around 4 minutes, popular with French Press and cupping. Either combination, and anything in between, can yield clean and balanced results, and can often show off slightly different facets of a coffee’s character, so experimenting is recommended.Brew Guides
Here we recommend resting your coffee for even longer, in our bars in Aarhus we try to use coffee that has been roasted more than 3 weeks ago for espresso. Espresso is also measured slightly differently, here we measure the ratio of dry coffee to the yield of espresso in the cup. For this we recommend placing a small set of scales under your cup as you brew, to measure the weight of espresso as it falls. When we brew our coffees, we recommend starting with a 1:2 ratio of dry coffee to espresso yield, and using the same rules as above to adjust grind size.