Water constitutes around 90% of a typical espresso and approximately 98% of a brewed coffee.
The better you look after your water, the better your coffee will be.
Water Hardness
Across the Uk there are varying degrees of hardness in water. Knowing how hard (or soft) your water is will help determine whether it is worth taking action to improve your coffee brewing.
Your local water company is obliged to publish water quality data and you can often do a postcode search on their site.
Calcium & Magnesium
These two minerals help carry flavour. If you have the right amount of them you will better appreciate those flavour notes on the coffee bags.
Soft water can contain too little of these minerals. Flavour will be difficult to determine and your coffee might taste weak.
Hard water contains too much of these minerals. Your coffee can taste heavy as a result.
Alkalinity
In part linked to mineral content is alkalinity. This determines the ability of the water to buffer the acidity in the coffee.
With the correct alkalinity, the acidity in your coffee will be balanced and enjoyable.
Soft water can have low alkalinity which can result in your coffee having a sour or sharp character, particularly lighter roasts.
Hard water is associated with high alkalinity and this can overpower the acidity creating a flat coffee.
Water Temperature
Heating your water to the correct temperature for coffee brewing is probably just as important as the quality of the water you use.
If the water is too hot, control of extraction is difficult and you risk dissolving undesirable compounds into your brew.
Too cold and the water might not have enough energy to dissolve enough solids into your brew, resulting in a sour, underextracted coffee.
