Before coffee extraction, coffee bean is ground into a portafilter. After which we will do levelling, tidying, and tamping of the coffee powder in the portafilter, resulting in a beautifully flat, well distributed coffee bed – the coffee puck – ready to have its first bath under the shower head.
But have you ever wondered the condition of the coffee puck inside the portafilter after each coffee extraction? Besides looking at the flow of extraction, which is one parameter to determine whether an extraction is an optimal one, another indicator is to view the status of the puck after extraction.
At times, some people may wonder whether the film or puddle of water that stays on top of the coffee bed after each extraction is a matter to be concerned about, since it has been generalized mostly by many that a wet, soggy coffee puck equals to poorly textured beverage with stagnant flavour. We would like to assure you that this is not necessarily the case, and there is nothing to worry about.
First, let us see how coffee is extracted from a semi-automatic home espresso machine. When we engage the machine to start coffee extraction, water will start to flow through the boiler / heating element to the group head, ultimately through the shower screen before it flows onto the coffee bed. The water will occupy the space / gap between the coffee bed and the shower screen when the machine pump is engaged, and seeps through the bed.
At the end of extraction, the brew valve inside the machine opens and releases pressure. The water simultaneously will run down a pipe and into the drip tray. Since water does not compress under pressure, and there is no pressure to push water out of the portafilter basket once coffee extraction stops, the remaining water that did not manage to flow out will thus be resting on top of the coffee puck in the portafilter basket.
It is recommended that after an extraction shot is pulled, wait for a few seconds and the last few drip of water to drain from the portafilter. Then remove the portafilter, press on the surface of the coffee puck with your fingers. It should feel nicely firm, with an appropriate film of water OR moisturized sheen on the coffee bed. Proceed to knock the pack out from the portafilter. The ground pack should come out as one intact piece – this indicates an ideal extraction dose.
But what if the coffee puck turns out otherwise than what is described above? If the ground pack looks or feels hard and almost dry, it means that the final extraction flow rate is slow, the taste of the coffee is inclined towards the bitter side.
The said scenario also demonstrates too high a dosage of coffee. When this happens, the coffee bed will seem too full for the portafilter to contain, resulting in the top of the coffee bed touching the shower screen. The ultimate extraction in this case will be very sluggish, uneven and inconsistent. The consequential taste is going to be bitter too.
The “overfill” of the filter basket in the portafilter means there is no room for the coffee grind to expand, and at the same time it is putting pressure on both the gasket ring and the shower screen of your machine. In time to come, this continuous, accumulated “soft” friction and pressure on the 2 components will lead to faster wear and tear of both. Another issue that will happen here is the clogging of the shower head.
On the contrary, if the puck turns out too soggy, it means your dosage of coffee is too low. This low dosage of coffee creates a gap between the coffee bed and the shower screen, allowing more excess water to enter, filling up this “headspace”. Once extraction ends, and the portafilter is dislodged from the group head, the remaining excessive water that did not manage to flow out from the portafilter will appear as a puddle of water on top of the coffee bed, resulting in a muddy soggy puck.
Furthermore, in this case, the flow rate from extraction will always be very quick with lots of channelling occurrences. The finishing espresso will taste sour, look watery, thin and lacking in volume.
Well, after knowing the condition of your coffee pucks, what to do next? For a start, you can tune the grind size OR the dosage of coffee. Soggy watery packs mean you had a coarse grind size OR a low dosage of coffee. In this case, adjust your grind size to a finer setting OR increase your coffee dose. Execute the opposite action for a coffee puck that is dry and hard.
All in all, if you need to select in the context of not getting that “perfect” puck, a wetter puck would be a better outcome than a dry one since per mentioned earlier, a dry, hard ground pack causes faster wear and tear to the shower head and the gasket ring eventually.
In addition, fret not on the condition of the resulting coffee puck since it is the coffee beverage that we are going to savour at the end of the extraction, not the puck itself. If, regardless the state of the puck, the final extraction flavour turns out superb and fits your palate, then there is no need to be too concerned about the state of the ground pack.
Coffee extraction is not merely, and it is more than a single, straightforward focus on the puck condition. The coffee puck is just one of the many indicators or clues that points to us the results of our shots.
Pulling a coffee / espresso shot is an art, a craft to learn, explore and enjoy. The espresso machine provides us the ready built-in functions and features to extract, but the final application still lies in our hands. With each day in the process of extraction, we discover and learn new things, ways to improve our techniques, adjust our applications to achieve a better coffee each time.
In no time, we will be sufficiently dexterous and skilful in obtaining what we always called the “optimal” coffee according to each individual preferences and expectations. Hence for now, just enjoy the art of coffee making. You will be enthralled and amazed 😊