What's in your water
Your kettle's biggest ingredient isn't coffee — 5 min
A cup of filter coffee is about 98.5% water, and none of it is neutral. Water arrives carrying dissolved minerals, and those minerals do real work: calcium and magnesium — general hardness — help pull flavour compounds out of the grounds, with magnesium especially good at grabbing the bright, fruity ones. Bicarbonate — alkalinity — is a chemical buffer that neutralises acids in the cup.
Both are dials, not villains. Too little of everything (distilled or reverse-osmosis water, alone) brews flat, sour, hollow coffee: nothing to extract with, nothing to cushion. Too much hardness and alkalinity brews dull and chalky, mutes the acidity you paid for, and lines your kettle with scale.
In the app
The rest of this lesson is in the Blend app — with the interactive widget and the practical brew.
Finish this lesson in the app.
The interactive widget, the footnotes, and the practical brew you can taste. Free on iOS and Android.