Water is half the recipe

We ship the same lot to a café in Brooklyn and a café in Rotterdam. Same roast date, same grinder, same recipe card. The Rotterdam cup comes out rounder and slightly flat; the Brooklyn one is sharper and thinner. Nothing about the coffee changed. The water did.

What the water is doing

Brewing water is mostly a solvent, and what is dissolved in it decides what it can pull out of the grounds. Magnesium extracts fruit and aromatics. Calcium pulls body and heavier sweetness. Bicarbonate buffers acidity — useful in small amounts, ruinous in large ones, because it neutralises exactly the brightness you paid for.

Too little mineral and the cup is hollow and washed out, no matter how fine you grind. Too much and it turns chalky and dull. Most tap water in northern Europe leans hard toward the second problem.

Where to start

You do not need a laboratory. A cheap TDS meter and a hardness test strip will get you most of the way: aim for roughly 70 to 90 ppm total hardness with alkalinity under 40. If your water sits well outside that, filtration will do more for the cup than a new grinder.

If a coffee tastes flat everywhere except at origin, suspect the water before you blame the roast.

We test the water at every wholesale account we open and send the numbers with the first delivery. It is the cheapest fix in the whole chain.