People come into the café and ask which grinder to buy, and I almost always answer with a question about their water. It throws them. But a good grinder poured through bad water gives you a precisely-ground bad cup. Water is somewhere between 98 and 99 percent of what's in your mug. It's worth thinking about for five minutes.
Coffee is a solvent problem. Water pulls flavor out of ground coffee, and how much it pulls — and which parts — depends on what's already dissolved in the water. Too pure, and it strips everything indiscriminately, giving you something sour and thin. Too hard, full of calcium and magnesium and whatever your city adds, and it can't grab the good stuff, so the cup comes out dull and flat. There's a window in the middle, and most tap water is sitting just outside it.
The easy version
If you don't want to think about it at all: buy a jug of low-mineral bottled water — the cheap kind labelled around 50 to 100 parts per million of dissolved solids — and brew with that. You'll taste the difference immediately, especially in lighter coffees. That's the whole tip. You can stop reading here and your coffee will be better tomorrow.
The cheapest upgrade to home coffee isn't a grinder. It's the water you were going to throw the coffee away in anyway.
The five-minute recipe
If you want to make your own and never buy a jug again, here's what we mix at the roastery for cupping. Start with distilled or reverse-osmosis water — something with essentially nothing in it. Then add minerals back in deliberately. The two-jug method is the simplest:
- In one bottle, dissolve a small amount of Epsom salt (magnesium) into distilled water — this brings extraction and brightness.
- In a second bottle, dissolve baking soda (bicarbonate) into distilled water — this is your buffer, the thing that keeps a sharp coffee from going sour.
- To brew, add a measured splash of each concentrate to a liter of distilled water. We use about a teaspoon of each per liter as a starting point and adjust to taste.
The exact numbers matter less than the principle: a little magnesium for clarity, a little bicarbonate to keep it civil, and otherwise get out of the way. Mix a batch, brew the same coffee you drank yesterday, and taste them side by side. If the new cup is sweeter and rounder, you've found your window. If it's flat, you've gone too soft on the magnesium. Adjust by feel.
It's a five-minute job that you'll do once and forget about. And it's the single change that's made the most coffees taste better for the most people we've handed a cup to. Long before the grinder.
← Back to journal