Coffee is mostly water. The quality of water naturally affects cup result. Coffee is often considered to be a water containing small coffee particles, but it is ideally a clean solution in which various tasty chemicals are completely dissolved. Except, the espresso is a colloidal solution which soluble and unsoluble matters exist in the liquid.
The ideal water for coffee is soft water which contains less minerals, rather than mineral rich hard water. The soft water with less soluble substance dissolved in is more capable to dissolve coffee nutrients. The hard water which already dissolved minerals within is less capable to dissolve substance in it.
The following article is a good example of how a coffee shop can actually prepare special water to differentiate the cup quality.
Hardness of Water and Brewing Method
It is found interesting that coffee brewing methods are developed differently depending on the areas of the world. In Italy, where hard water is common, the espresso has been developed. While pretty much all the brewing methods started in Europe, espresso has been notably developed.
Japan, the place the most of contemporary pour over methods have been developed, has great access to soft water throughout its land. The two major coffee drinking cultures evolved based on their natural water quality.
But now is the time, coffee chooses water rather than water chooses coffee. The trend is shifting from Starbucks driven espresso to third wave driven pour-over, shift of hard water to soft water could be undergoing water trend.
Hardness of water you use
Technically, there seems to be other factors contributing to determine hardness of water besides minerals, but the following classification chart(from wikipedia) by United States Geological Survey gives a good idea.
If you brew coffee at home, knowing the water hardness in your area might be helpful.
There is some useful study I found about “Mineral Content of Tap Water in Major North American Cities”.
Or for the bottled water users, this study is useful.
Comparing the tastes between hard water brewed coffee and soft water brewed coffee could be an interesting coffee science project.
(photo credit: rootseven)