Dialling in: the loop that turns a bad shot into a good one

Dialling in is adjusting your grinder until a given coffee tastes right on your machine. That is the whole of it, and the reason it takes people so long is not that it is difficult but that they change several variables at once and cannot tell which one helped.

The underlying idea is extraction. Water passing through ground coffee dissolves the soluble material, and how much it dissolves depends mostly on how long it is in contact and how fine the grind is. Too little extraction tastes sour, thin and sharp; too much tastes bitter, dry and hollow. Almost every espresso fault is one of those two, and the grinder is the control that moves you between them.

This is a decision loop rather than a physical skill, which is why it can be written down. The parts of espresso that are genuinely a physical skill — distributing grounds evenly and tamping consistently — are covered here as what to hold constant rather than as something this page can teach you to do.

The main control

Grind size

Sour, thin, sharp

Under-extracted — grind finer

Bitter, dry, hollow

Over-extracted — grind coarser

The discipline

One variable at a time

1. 1

   Step 1: Fix your dose and leave it alone

   Weigh the dry coffee and use the same weight every time. It does not matter enormously what that weight is — what matters is that it stops being a variable. A scale reading to 0.1g is the single most useful thing you can buy for this and costs less than a month of café coffee.

   You will know it worked when: One variable removed.

2. 2

   Step 2: Decide the ratio you are aiming for and weigh the output

   Espresso is described as a ratio of dry coffee in to liquid out. Pick one, weigh the shot rather than judging it by eye, and keep it constant while you adjust. The calculator on the home espresso page does this arithmetic; it deliberately states no correct ratio, because there is not one.

   You will know it worked when: A target you can hit repeatably.

3. 3

   Step 3: Pull a shot and time it

   From the moment the pump starts to the moment you stop. The time is not the goal — the taste is — but it is the fastest diagnostic you have, because it tells you which direction the grind needs to move before you have even tasted it.

   You will know it worked when: A number to compare against the next one.

4. 4

   Step 4: Taste it, and name the fault

   Sour, sharp, thin and lacking sweetness means under-extracted. Bitter, drying, hollow and lingering unpleasantly means over-extracted. This naming step is the one beginners skip, and without it the adjustments are guesses.

   You will know it worked when: A diagnosis rather than a hunch.

5. 5

   Step 5: Change the grind, and nothing else

   Finer if it was sour and running fast; coarser if it was bitter and running slow. One adjustment, in one direction, then repeat the loop. The temptation to also change the dose, the tamp and the ratio in the same round is what turns a ten-minute job into a fortnight.

   You will know it worked when: A shot that moved in a known direction.

6. 6

   Step 6: Purge the grinder after adjusting

   A small amount of coffee at the old setting stays in the grinder. Grinding a little through and discarding it before the next shot removes the commonest source of confusing results — a shot that is a blend of two settings.

   You will know it worked when: A shot that reflects the setting you chose.

7. 7

   Step 7: Stop when it tastes good, not when it hits a number

   Published times and ratios are starting points and nothing more. Coffees differ enormously by roast, age and origin, and the correct setting for one bag is the wrong setting for the next. The target is the cup.

   You will know it worked when: A dialled-in coffee, and the loop learned.

• Distribution and tamping — consistency matters more than technique — Uneven grounds let water find a fast path through, which produces a shot that is simultaneously over- and under-extracted and tastes confusing rather than simply wrong. What matters for dialling in is that you do the same thing every time, not that you do any particular thing. The physical feel of an even tamp is a hand skill and this page will not pretend to transmit it.
• The dose, once chosen — Changing the dose changes the depth of the coffee bed, which changes the resistance, which changes the time — so a dose change looks exactly like a grind change and you cannot tell them apart afterwards.
• The basket — Different baskets behave differently. Swapping between them mid-process is another hidden variable.
• Water — Water chemistry genuinely affects taste and it also affects your machine. It is worth settling on one supply and leaving it, both so it stops being a variable here and because it is the thing that determines how long a machine lasts.
• Freshness, which moves under you — Coffee degasses for days after roasting and continues changing for weeks. A bag that was dialled in on Monday may need adjusting by Friday, and this is normal rather than a sign you did it wrong. It is also why chasing somebody else’s published setting is futile — their bag is a different age from yours.