The basket is overfilled or underfilled
The puck shows the imprint of the shower screen, or sits so low that water pools above it.
Applies to: Espresso machine, Espresso
What the basket is telling you about the dose
CoffeeHQ explanation
A basket is a container with a fixed volume, and the number stamped on it is the dose it was designed around. Between the top of the tamped coffee and the shower screen there has to be a small gap. Coffee swells when it wets, and the first water needs somewhere to spread before it starts pushing through. That gap is headspace, and the dose is what sets it.
Too much coffee removes the gap. The dry puck presses on the screen, cannot expand, and water arrives at one point instead of across the surface; the shot chokes or channels, and the puck comes out with the screen and its screw printed into it. Too little coffee leaves a deep pool of water above a thin bed. The pool disturbs the surface as it fills, the bed offers little resistance, and the shot runs fast and tastes thin. The spent puck is wet and falls apart.
Causes, most likely first
There are 3 likely causes, listed with the most probable first. Work down the list and change one thing at a time, so that when the problem goes away you know which change fixed it.
Cause 1 of 3 · Commonly the cause
Dose outside the basket's design range
- How to check
- Do you know what dose range your basket is made for?
- What to change
- Work within the range stated for the basket, commonly around 14-18 g for a standard double.
Cause 2 of 3 · Reported, not independently verified
A recipe copied from someone using a different basket
- What to change
- Doses do not transfer between baskets. Establish your own within your basket's range.
Cause 3 of 3 · Reported, not independently verified
Grinder retention making the actual dose lower than the weighed input
- What to change
- Weigh the ground coffee rather than the beans.
If none of these fixes it
Check the cleaning and descaling guide. Equipment that needs maintenance can cause several of these symptoms at once, and no change of recipe will correct it.
Work through it for your setup
The causes above are general. These go to the part of a diagnostic that takes this symptom one check and one change at a time.
- Espresso puck preparation: dose
- Make my coffee better: Espresso machineEvery reading for this brewer: the check, and the one thing to change first
Change the dose by a gram before touching the grind
Weigh what actually lands in the basket, not what went into the grinder: a grinder that holds coffee back can leave you a gram or two short without your knowing. Then move the dose one gram towards the basket's rated figure and pull the same yield. A gram is a large change in a basket this size, and it will alter the shot time on its own. Only once the puck surface comes out clean and shallow should you return to the grind.
When the recipe was written for a different basket
A recipe that says 18 g assumes an 18 g basket. Baskets sold as 14, 18 and 22 g look similar from above and differ in depth, and the basket supplied with many home machines holds less than the recipes people copy. Light and dark roasts also fill a basket differently: darker beans are less dense, so the same weight takes up more room. If a published recipe will not fit, the recipe is wrong for your basket, not your technique.
Easily confused with
- A grind that is too fine — Both choke the shot. An overfilled basket leaves the screen's imprint on the puck and resists grind changes; a grind that is merely too fine leaves a clean surface and responds as soon as you go coarser.
- A wet puck on a machine with no three-way valve — A soupy puck from a correctly dosed basket is normal on those machines. It only points to under-dosing when the shot also ran fast and thin.
What not to change at the same time
Do not change dose and grind in the same shot. Both alter resistance, and a one-gram dose change can easily be mistaken for the effect of the grind adjustment made alongside it.
How to tell it is fixed
The spent puck knocks out in one piece with a flat, shallow surface and no mark from the screen, and the shot time now moves predictably when you adjust the grind.
If that changed nothing
If the right dose for the basket still chokes at any sensible grind, check for a puck screen or a thick gasket taking up the headspace, and try the basket without them.
Espresso dose and yield calculator — Enter the dose your basket is rated for and read off the yield for the ratio you want, so the target changes with the dose instead of being carried over from another basket.