Espresso Shot Not Tasting Right? Read Your Puck and Find Out Why

The spent coffee grounds in your group handle are called the coffee puck. Examining properties of the puck, including its surface and structural integrity, provides valuable feedback on the quality of the shot. Variables like consistency, colour, and adhesion can indicate whether ideal extraction took place or if flaws developed during the brew that could produce an imbalanced flavour. By regularly inspecting coffee pucks, baristas can tweak parameters like grind size and dose in order to achieve optimized extraction yield and flavour from each shot. Flavour is always the end goal, so if you have a less then ideal puck but perfect flavour, there’s no need to troubleshoot through puck analysis. But if your flavour is failing, this guide might just get you back on track.

Cracks In Your Puck

Cracks compromise the coffee puck, promoting uneven saturation and poor extraction. Fissures often stem from:

Aggressive Handling: Tapping or banging the portafilter can fracture the puck edges, enabling water to rapidly channel around the cracks.

Overzealous Tamping: Excess tamping pressure can cleave cracks across the surface, creating low resistance pathways for water to bypass much of the grounds.

To prevent cracking and uneven flow, handle the portafilter gently when distributing and grooming. When tamping, use moderate, consistent pressure to evenly consolidate the grounds. This encourages water to penetrate uniformly during brewing for balanced extraction. With care to avoid damaging the puck, you can achieve quality, even saturation.


Channelling mars extraction when water flows too rapidly through the coffee grounds, creating tunnels that lead to uneven saturation. Telltale signs in the spent puck include:
Rapid Flow: If espresso gushes out too quickly, preferential flow paths have likely formed inside the puck.

Dripping: The early drops emerging may wiggle about instead of a steady, centered stream, indicating uneven extraction.

Density Variations: The puck’s surface may appear mottled, with dense areas next to spongy spots as water flows around slower-saturating areas.

Fissures: Jagged cracks clustered near the puck’s edges betray channels around the edges, leading to poor extraction uniformity.

Observing these visual cues signals channeling has occurred, requiring grind size adjustments to restore even, controlled flow and balanced extraction.

Sloppy & Detached Puck

If the spent grounds bloat and detach from the filter basket sides, this floating puck signals over-extraction and boosts bitterness. Trigger causes include:

Ultra Fine Grind: An overly powdery grind lacks resistance to counteract infusion pressure. Combined with skimping on coffee dose, swelling occurs as water hyper-saturates the puck.

Creeping Flow: When drips emerge at a sluggish pace resembling diluted syrup, it betrays significant back pressure from swollen, choked grounds hindering flow.

Fixes involve adjusting the grind towards coarser particles to reestablish flow impedance and control saturation. Additionally, dose more grounds to provide greater resistance while achieving proper water-to-coffee contact time. With puck adhesion maintained, balanced extraction can be restored.

Super Fine Grind Compensating For Low Dose

When an overly fine grind muffles the coffee bed into an impenetrable barrier, extraction suffers. Hallmarks include:

Dripping: Instead of a rich, viscous stream, drips emerge reluctantly in a narrow, drizzly trickle indicating highly restrained flow.

Messy Flow: Rather than a smooth consistent pour, coffee emerges erratically in weak, pulsing spurts from the saturated but obstinate puck.

Lackluster Crema: A thin layer of pale bubbles with little persistence betrays poor extraction from the chokingly dense grounds.

Blame excessively powdery grinds that compact into an impassable mass at typical infusion pressures. Light dosing further diminishes the puck’s flow channels. To revive extraction, shift the grind coarser. This restores the passageways for evenly dispersed infusion that builds multidimensional flavour.


Reading the coffee puck provides a window into the complex dynamics occurring during brewing to shape flavour. Becoming fluent in identifying extraction flaws evident in spent grounds is key for continually improving one’s craft. Scan for signs like cracks spreading unevenly saturated regions, tunnels hinting at channel risks diverting flow, swollen detachment pointing to overwrought grounds, or fluid trickles rather than a viscous stream that betray impermeable packing. Though subtle to the untrained eye, for the attentive barista artfully prepared pucks reveal a great deal, directly connecting visual diagnostics to adjusting parameters like grind size, dose, or prep method when pursuing the ideal, balanced cup. Inspecting this leftover record of brewed coffee equips one to stepwise master nuances of extraction through experimentally honing technique.