The puck sticks to the shower screen
On unlocking the portafilter, the spent puck has lifted out of the basket and is stuck to the group.
Applies to: Espresso machine, Espresso
Why the puck comes away with the group
CoffeeHQ explanation
When a shot ends, the puck is a wet, swollen cake sitting just under the shower screen. On machines with a three-way valve, pressure above the puck is released suddenly at that moment, which pulls the surface of the cake upwards. If the cake was already touching the screen, or the screen is tacky with old coffee oil, the puck lifts out of the basket and stays on the group when you unlock the handle.
It is a nuisance more than a fault. But it is also a reliable sign that there was no gap between coffee and screen during the shot, and a puck with no gap cannot wet evenly. The same condition that makes it stick is likely making the shot channel.
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 too large for the basket, leaving no headroom
- What to change
- Reduce the dose by a gram or two and check the puck clears the screen when locked in.
Cause 2 of 3 · Reported, not independently verified
A puck screen taking up the remaining headroom
- What to change
- Reduce the dose to account for the screen's thickness, or leave the screen out.
Cause 3 of 3 · Reported, not independently verified
Residue on the shower screen giving the puck something to adhere to
- What to change
- Brush the screen after each session and backflush at the interval the manual specifies.
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.
- Make my coffee better: Espresso machineEvery reading for this brewer: the check, and the one thing to change first
- Care, by sign and by the manual: espresso machineThe habit with every use, what to check and what triggers a job
Make room above the coffee
Reduce the dose by a gram and pull the same yield. If you use a puck screen, remember that it occupies the headspace too: a dose that fitted without one may not fit with one, and the dose has to come down to make room for it. Then clean the shower screen, because fresh oil is slippery and old oil is glue.
Easily confused with
- An overfilled basket — Usually the same problem seen from the other side. Overfilling is the cause; a puck stuck to the screen is one of its effects.
- A group that needs cleaning — If the puck sticks at a dose that used to release cleanly, nothing about the coffee has changed and the screen has become dirty.
What not to change at the same time
Do not lower the dose and remove the puck screen in the same shot. Each frees headspace, and you will not learn which one your basket needed.
How to tell it is fixed
The puck stays in the basket when the handle is unlocked and knocks out whole, with a flat top that shows no imprint of the screen or its screw.
If that changed nothing
A puck that still lifts at a modest dose on a clean screen may simply be how your group releases pressure. If the shots taste right and flow evenly, wait a few seconds before unlocking and let the puck settle; that is a habit, not a repair.