Water chemistry, in a brewing context, refers to the mineral composition of the water used to mash and sparge — calcium, magnesium, sodium, sulfate, chloride, and bicarbonate are the six ions homebrewers typically track, and their relative concentrations shape mash pH, yeast health, and the perceived balance between hop bitterness and malt sweetness in the finished beer.
Two ions that pull perceived flavor in opposite directions
Sulfate sharpens and dries perceived hop bitterness — the mechanism behind Burton-on-Trent's historic association with assertive English pale ale. Chloride rounds out and fills in perceived malt character instead — closer to what Dortmund's water, high in both minerals at once, contributes alongside sulfate's sharpness. Building water toward a specific sulfate-to-chloride ratio, rather than adjusting either mineral in isolation, is the real lever most brewing-salt recipes are actually working with.
Historic city water profiles are a real, checkable reference point
This site's own water reference pages cover the historic mineral profiles of brewing cities like Burton-on-Trent, Pilsen, and Dortmund specifically because those cities' water shaped which styles developed there — a genuinely useful starting reference for a brewer deciding what water profile to build toward for a given style, alongside PeriodicDeck's background on what each of these ions actually is chemically.