An espresso machine heats water and pushes it through a compact bed of finely ground coffee at high pressure, conventionally around nine bar. The pressure is not what makes the coffee strong. It is what makes it possible to force water through grounds that fine, in under a minute, at a ratio of about two parts water to one of coffee.
The parts that matter to the shot are few. The group head delivers water through a shower screen. The portafilter holds a metal basket; the basket holds the coffee. A pump or lever supplies pressure. A boiler or thermoblock supplies heat, and on many machines the same or a second boiler supplies steam through the wand.
The basket deserves a moment's attention. A single-wall basket has many fine holes and lets the coffee itself create the resistance. A pressurised basket has one small exit hole that creates resistance regardless of the grind. Most espresso advice, including this course, assumes single-wall. If your shots do not respond to grind changes, check the underside of the basket before anything else.
An espresso recipe is three numbers. Dose is the dry coffee in the basket, chosen to suit the basket: a basket sold as 18 g works best within a gram or so of that. Yield is the weight of espresso in the cup. Dividing yield by dose gives the ratio.
A ratio around 1:2 — 18 g in, 36 g out — is the common modern starting point. Shorter ratios, towards 1:1.5 and below, are thicker and more intense and are usually called ristretto. Longer ones, towards 1:3, are thinner and are usually called lungo. The boundaries are not fixed and cafés use the words differently.
Time is the result, not the target. With a sensible dose and yield, a shot that takes somewhere around 25 to 35 seconds is in the range most recipes assume. A shot inside that range can still taste bad, and one outside it can be excellent. Time tells you whether the grind is in the right neighbourhood and whether today's shot matched yesterday's.
Yield from an 18 g dose at four ratios
CoffeeHQ diagram
1:1.527 gShorter — often called ristretto
1:236 gThe common starting point
1:2.545 gLonger
1:354 gLong — often called lungo
Axis runs from 0 to 60 g.
The whole span from a short shot to a long one is 27 g of liquid — under two tablespoons. That is why yield is weighed and not judged by eye.
Arithmetic: yield = dose × ratio. The names are common usage with no fixed boundaries, and cafés apply them differently.
Water under pressure takes the easiest path. If one part of the puck is less dense than the rest, water rushes through it, over-extracting that path and barely touching the coffee beside it. Puck preparation is the work of making the bed uniform so that there is no easiest path.
The sequence is simple. Grind into the basket or a dosing cup and weigh the dose. Break up clumps and even out the density, most reliably by stirring through the full depth of the grounds with fine needles — the Weiss Distribution Technique, or WDT. Level the surface. Tamp once, straight down, firmly enough that the bed stops compressing. Tamping harder than that does little; tamping crooked does a lot.
Leave some headspace between the puck and the shower screen. An overfilled basket presses against the screen, cannot expand as it wets, and often chokes or channels. A simple check: a shallow, clean puck surface after the shot, without the imprint of the screen screw.
Puck preparation, in order
CoffeeHQ diagram
1Weigh the doseTo suit the basket, within about a gram of its rated size.
2DistributeStir through the full depth with fine needles to break clumps and even out density.
3LevelA flat surface before tamping, so the tamp compresses evenly.
4Tamp once, straight downFirm enough that the bed stops compressing. Level matters more than force.
5Check headspace, then lock in and startThe puck should not touch the shower screen. Start the shot promptly.
A common sequence for a single-wall basket. Tools and details vary; the aim at every step is a bed with no easier path through it.
Watch the shot as well as timing it. After a few seconds, dark drops should appear and gather into a steady, syrupy stream that lightens gradually in colour. From a bottomless portafilter you can see the underside of the basket: an even shot darkens across the whole surface at about the same moment and the streams merge into one.
Channelling shows as pale spots that appear early, jets that spray sideways, or one side flowing before the other. In the cup it has a recognisable signature: sour and harsh at the same time, because some coffee was barely extracted and some was stripped. Grinding finer into a channelling puck usually makes it worse, which is why distribution is checked before grind.
Crema, the foam on top, is carbon dioxide and coffee oils emulsified under pressure. It says something about freshness and roast and very little about quality. A thick crema on a stale-tasting shot is still a stale-tasting shot.
Your task. Enter your basket's dose and work out the yield for 1:1.5, 1:2 and 1:2.5. Write the three target weights on a note by the machine before you pull anything.
What to notice. The difference between a ristretto and a long shot from the same dose is only a couple of dozen grams of liquid. Stopping by eye cannot hit that reliably; a scale under the cup can.
Exercise: One shot in three cups
Objective. Taste how an espresso changes from its first drops to its last.
You will need
An espresso machine and grinder, dialled in to a shot you like
Three small cups and a scale
Keep the same
Your normal dose, grind and total yield
A single uninterrupted shot
Procedure
Start the shot into the first cup.
At roughly one third of your usual yield, slide the second cup under the spouts; at two thirds, the third.
Stop at your usual total yield.
Taste each cup on its own, then pour all three together and taste the whole.
What to notice
Which third is thickest and most intense? Which is thinnest?
Where does sourness sit? Where does bitterness arrive?
Does the combined cup taste better than any single part?
Reading what you found
The early part of a shot is usually the most concentrated and sharpest, and the last part the thinnest and most bitter. That is why stopping a shot earlier or later changes its balance and not only its strength, and why yield is a flavour control.
What this cannot show
Swapping cups by hand is imprecise. The exercise shows a direction, not a measurement.
A different coffee, roast or ratio will divide differently.
Safety. Keep fingers clear of the group and the hot portafilter while moving cups.
A protocol for you to run. CoffeeHQ has not run it and reports no result from it.
A new machine owner has moved the grinder from one end of its range to the other. Every shot takes about the same time and looks about the same, with a thick pale crema. All of them taste thin and a little sour.
Reasoning it out
A grind change that large should move shot time dramatically. It did not, so something other than the coffee is setting the resistance.
A pressurised basket does exactly that: the single exit hole controls the flow whatever the grind.
Its foam looks like crema but is produced mechanically, which is why it is pale and thick on every shot.
Thin and sour suggests the coffee is barely extracting, which fits a coarse grind hidden behind an artificial restriction.
What to do
Turn the basket over. One small hole means pressurised. Either accept its limits and use it with pre-ground coffee as intended, or fit a single-wall basket and start dialling in properly — which also needs a grinder capable of fine espresso adjustment.
Tamping level and distributing evenly are physical skills. A description can tell you what a good puck looks like; only repetition, and looking at your own pucks, makes it consistent.
Comparisons worth making now
Bottomless or spouted portafilterA bottomless portafilter is a diagnostic tool; this explains what it shows and what it costs you in mess.
SCA brewing and espresso standards — Specialty Coffee Association (SCA)
Barista Hustle technical training content — Barista Hustle
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