Analysis
The flow rate starts high at 1.5 ml/s at 2s and continues to increase up to 7.2 ml/s by 14s while the pressure remains close to zero, then flow suddenly drops, finally stabilizing around 1.5 ml/s after 36s. The temperature drops by 14°C within 12 seconds, and then increases again.
Primary Issue
Severe Channeling: Indicated by the extremely high initial flow rates (reaching 7.2 ml/s at very low pressure) followed by a sudden drop and erratic behavior later in the shot.
Recommendation
Adjust: Puck Preparation
How:
- Implement WDT (Weiss Distribution Technique): Use a fine needle or tool to thoroughly declump and evenly distribute the coffee grounds in the portafilter before tamping. Ensure no areas are more dense than others.
- Focus on Even Tamping: Ensure a consistent and level tamp. If you are using a calibrated tamper, ensure proper contact and consistent pressure (around 30 lbs).
Why: The extremely high initial flow at near-zero pressure indicates a very weak and uneven puck. WDT will break up clumps and distribute the grounds evenly, eliminating areas of low resistance. A level tamp ensures uniform density across the puck, preventing water from finding preferential paths through the puck.
What to Look For Next Shot
A more gradual increase in flow during the initial phase, without the sudden spike to 7.2 ml/s. A more stable and consistent flow rate throughout the shot, without drastic fluctuations.
Important Context
Addressing the puck preparation is crucial before considering any grind adjustments. If channeling persists after implementing these puck prep improvements, only then should you consider adjusting the grind finer. The large temperature instability should be addressed to ensure accurate brewing.
Advice by Google Gemini