Planting, harvesting, processing, exporting, roasting, grinding, brewing. These are some of the steps that we need to stick with if we want to obtain a cup of coffee. But when it comes to quality, people often overlooked the part played by the water.
In fact, water has to be considered one of the element that will affect the most our cup of coffee, no matter if you have the best beans or the best equipment in the world. We do have to really care about the impact of water on coffee cause it makes up more than 92% of an espresso recipe and more than 98% of a black coffee. It can accentuate its acidity or take it out completely. It can extract lots of fruity and floral notes and it can give us a full body or a flat one. So, what affect the taste of the final cup? Water has a lot of minerals with negative and positive charge. What we have to do is to try to find a balance bonding all the elements.
TOTAL HARDNESS (GH)
Basically, it represents Calcium and Magnesium levels in the water. They both required to extract flavours out in the cup. Calcium is responsible for enhancing body while Magnesium attracts acid molecules giving a more sweetness and citrus tastes. Calcium is also responsible for limescale issues because it doesn’t dissolve properly in water.
CARBONATE HARDNESS (KH)
Carbonate Hardness or temporary hardness are responsible for buffering phenomenon. Carbonate and bicarbonate try to keep the PH of the water stable (an ideal PH range is between 6,5 and 8 according to SCA standards). Keeping PH stable is really important if we want to obtain a balance taste. Low carbonate hardness brings too much acidity in the cup while high carbonate hardness pulls out any acidity leaving a flat cup.
PH is a scale that measure how alkaline/acidic water is. The range goes from 0 to 14 with 7 as neutral. Lower PH indicates more acidity while higher PH indicates more alkaline.
As we know, the water in London are too high in hardness causing limescale issues inside coffee machine, reducing heating efficiency, restricting water flow and damaging valves and orifices.
We can treat the water in different way such as reverse osmosis, filtration or water softener.
This is the most expensive water treatment designed mostly for coffee shops with high volumes. This was the traditional system to obtain a distilled water without any minerals and all the other ions like chlorides and sulphates. However, at this stage, we cannot brew coffee cause we will obtain a flat cup without any flavours. With the blending reverse osmosis, we can now add the minerals we need depending on what we want to obtain.
Carbon filters are less expensive than a reverse osmosis system but they will only remove off-flavours without any change regarding mineral content.
This system also suits at home. It works with ion exchange process in which water pass through a bed called resin. The resin is responsible to reduce the hardness; the hard minerals pass through the resin and at the same time some sodium or potassium ions are released into the water. The resin must be recharged adding some sodium hydroxide or sodium chloride when it is saturated by the hard minerals (mostly calcium and magnesium). Also, I suggest to place a carbon filter to remove any unpleasant flavours due to sodium ions.
In conclusion, the perfect water doesn’t exists. You just have to play balancing the minerals and keep tasting to improve your water quality.