Dialling In Espresso at Home Without Wasting Half a Bag

If the shot tastes sour and thin, grind finer. If it tastes bitter and drying, grind coarser. That one rule fixes most bad espresso made at home, and the rest of this is about applying it in an order that does not cost you half a bag.

Three numbers, and only three

Everything you do at the machine shows up in three measurements.

• Dose — the weight of dry ground coffee in the basket.
• Yield — the weight of liquid espresso in the cup. Weigh it rather than judging the level by eye; crema volume changes with grind and roast date and will mislead you.
• Time — from the moment the pump starts to the moment you stop the shot.

Yield divided by dose is your brew ratio. 18g in and 36g out is 1:2, the standard modern espresso ratio. Shorter ratios such as 1:1.5 give more body and less clarity. Longer ones, 1:2.5 or 1:3, give more sweetness and more risk of thin, papery flavours.

A sane starting point

• 18g of coffee in an 18g basket
• 36g of espresso in the cup
• 25 to 30 seconds from the pump starting
• Water around 93°C; the usable range is 90 to 96°C, lighter roasts higher, darker roasts lower

If your basket is 15g or 20g, dose to the basket and hold the ratio: 15 in, 30 out; 20 in, 40 out. Scales that read to 0.1g are the most useful thing you can buy after the grinder.

Change one variable at a time

The usual way people burn through coffee is by moving the grind, the dose and the yield together, getting a better shot, and having no idea which change did it. Lock the dose. Lock the yield. Move the grind only, one step, and taste.

A worked example. 18g in, 36g out in 18 seconds, tastes sharp and sour: water ran through too fast and took the acids without the sugars. Go one step finer, purge the old grounds in the grinder, pull again. Land at 26 seconds and sweeter and you are done. If it takes 40 seconds and tastes bitter and drying, you have gone past it; come back half a step.

Grind is the main lever by a distance. Pressure profiling, basket brand and water recipes come later, once you can hit the same time three shots running.

Distribution and tamping

A level tamp with steady pressure is enough. The exact force is close to irrelevant, and beyond about 15kg you compress nothing further.

Channelling, though, is real. Water is lazy and finds the loosest path through the puck. When it does, part of the coffee is over-extracted and part is barely wetted, and the shot manages to taste sour and bitter at the same time. The signs are a stream that sprays sideways, one spout going pale far earlier than the other, or wildly different times from identical settings. The fix is stirring the grounds with a fine needle tool to break up clumps, then tamping level rather than hard.

Roast date changes what the grinder needs

Coffee gives off carbon dioxide for days after roasting, and in an espresso puck that gas gets in the way of an even extraction. Very fresh coffee is simply harder to dial in: shots channel, the crema comes out thick and foamy, and the same setting can behave differently two mornings running. Rather than chase it, give a new bag a few days and re-dial once it has settled.

Roughly seven to fourteen days off roast is where espresso settles down and becomes repeatable. Coffee roasted yesterday and coffee roasted last week are not the same thing to dial in, which is why every bag we send out carries a roast date rather than a vague best-before. We roast in batches from 100g to 4kg at three sites — Kensington and Monument in London, and Gurney in Penang — and the four UK satellite shops are supplied from the London roasteries. There is more on how we roast if the mechanics interest you.

Past three or four weeks open, aromatics fade and the coffee tastes flat whatever you do with the grinder. That is not a dialling-in problem.

Milk drinks want a different target

Milk brings sugar, fat and volume, and it flattens acidity. A bright, tea-like shot that is a pleasure black can vanish under 150ml of steamed milk. For flat whites and cortados, pull shorter, around 18g in and 27 to 32g out, to keep density and sweetness, and choose a heavier coffee. Iwa is the blend we would point you at for milk. The Brazil Fazenda Santa Cruz from Varginha, a pulped natural Catuaí, also has the body to hold up. For black espresso, go the other way: a longer ratio and a lighter coffee such as the Ethiopia Damo when it is in rotation, where clarity is the point.

The routine

1. Weigh the dose. Same number every time.
2. Pull one shot and write down dose, yield and time.
3. Taste it. Sour and fast means finer. Bitter and slow means coarser.
4. Change the grind only, one step, and purge the grinder before the next shot.
5. Repeat until it lands.
6. Record the setting alongside the coffee and its roast date.

Re-dial when you open a new bag, and expect drift as that bag ages. Keep beans sealed, at room temperature and out of the light, and buy what you will get through in three or four weeks. The current coffees all carry their roast date, and if you would rather taste something before committing to a bag, that is what the seven shops are for.