What is wrong with your shot?

How the diagnosis works

Espresso faults fall into two groups: faults of extraction and faults of material. Extraction problems — grind, dose, timing, puck prep — respond to adjustments you can make on the next shot. Material problems — stale beans, pre-ground coffee, a pressurised basket — do not respond to adjustment at all, which is why people chase grind settings for weeks and never improve.

The quiz separates the two before suggesting anything. If it finds a material problem, it says so first, because no amount of dialling in will help.

The four signals

Taste is the only measurement that matters, but it is ambiguous on its own — sour and bitter are easy to confuse, and a weak shot is not the same as an under-extracted one. The quiz combines taste with three objective signals that narrow the possibilities:

Signal	What it rules out
Shot time	Distinguishes under- from over-extraction when taste is ambiguous
Puck condition	Reveals channeling, under-dosing and over-filling
Equipment	Identifies problems that adjustment cannot fix

What it will not tell you

It cannot taste your coffee. Sourness in particular is easy to misidentify — what reads as sour is sometimes just acidity from a light roast, which is a feature rather than a fault. If the quiz suggests grinding finer and the shot gets harsh rather than sweeter, you were probably not under-extracted. Back up and try the opposite direction.

It also cannot tell you that your water is wrong. Hard water above 150 ppm total hardness and soft water below 50 ppm both produce faults that look exactly like grind problems. If adjustments are not working and the beans are fresh, check the water.

Common questions

Why does my espresso taste sour and bitter at the same time?

That combination almost always means channeling: water found fast paths through the puck, over-extracting those channels while the rest of the coffee under-extracts. Fix puck preparation before changing the grind.

How long should an espresso shot take?

25 to 32 seconds from pump on to pump off for a standard 1:2 ratio. Ristretti run shorter, lungos longer. Timing is a diagnostic, not a target in itself.

What does a soupy puck mean?

Usually that the dose is too small for the basket, so water pools above the puck instead of being forced through it. Increase the dose until the puck just meets the shower screen.

Does grind size fix a bitter shot?

Often, yes. Bitterness with a slow shot means over-extraction, so grind coarser one step. But if the puck was cracked or the beans are stale, grind will not fix it.

Can the quiz fix bad beans?

No. Stale beans cannot be rescued by any grinder or ratio change. If the coffee is more than a few months past roast, that is the first thing the quiz will tell you.