It started innocently. I bought a nicer bag of beans, made my usual cup, and it tasted roughly the same as the supermarket stuff. The internet, when consulted, was unanimous and slightly smug: it is the grinder, not the beans. The grinder is always where the trouble begins.
I had been using a cheap blade grinder for years. A blade grinder does not grind so much as assault the beans, producing a chaotic mix of dust and boulders. The dust over-extracts and goes bitter, the boulders under-extract and go sour, and you get both in the same cup. Once someone explains this you cannot un-know it, and you start eyeing your kitchen worktop with suspicion.
the consistency problem
The whole game with coffee, it turns out, is grind consistency. You want every particle roughly the same size so it all extracts at the same rate. Burr grinders do this by crushing the beans between two abrasive surfaces at a fixed gap, rather than smashing them with a spinning knife. Conical burrs, flat burrs, steel, ceramic; each has a small congregation of people online who will tell you the others are wrong.
I went for a hand grinder with steel conical burrs, partly on price and partly because the reviews kept using the word "stepless", which appealed to the part of my brain that likes a continuous adjustment over a clicky one. You twist a dial, the burrs move closer or further apart, and you dial in your grind by taste over several mornings. It is fiddly and a little bit wonderful.
retention, and other things I now care about
Then I learned about retention: the grounds that get stuck inside the grinder and don't come out, so today's cup is partly yesterday's stale coffee. There are people who tap, knock, and bellow-puff their grinders to chase out the last half-gram. I am not yet one of them, but I understand them now, which is its own kind of warning sign.
Here is the honest bit. The hand grinder made a genuine, obvious difference. The coffee got noticeably better, the kind of better you can taste without trying. Everything beyond that point, the second grinder I have been "researching", the scale that measures to a hundredth of a gram, the talk of single-dosing, is the long tail of diminishing returns where the hobby stops being about coffee and starts being about the kit.
So I am drawing a line. One good grinder, decent beans, a kettle I already owned. The cup is excellent and my bank account is intact. I give it three weeks.