Coffee Data Science
Shredded Cloth Filters in Espresso
An experiment to understand cloth filters
Previously, I found cloth filters speed up coffee flow by putting one at the bottom or the middle of the espresso puck. I decided to make a crazy experiment. What if I cut a cloth filter into small pieces and mix it into the puck?
Let’s find out!
I cut it up, wet the pieces, and dried them a little to insure they were damp but not soaked.
Then I mixed them into the coffee.
Equipment/Technique
Espresso Machine: Kim Express
Coffee Grinder: Niche Zero
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Shot Preparation: Staccato Tamping
Pre-infusion: Long
Infusion: Pressure Pulsing
Filter Basket: 20g VST
Other Equipment: Atago TDS Meter, Acaia Pyxis Scale
Results
The shot certainly came out strange with some major channeling.
From the bottom of the puck, the pattern was definitely indicative of slow flow and channeling.
Looking from the side, the puck is a bit fragile.
Metrics of Performance
I use two metrics for evaluating the differences between techniques: Final Score and Coffee Extraction.
Final score is the average of a scorecard of 7 metrics (Sharp, Rich, Syrup, Sweet, Sour, Bitter, and Aftertaste). These scores were subjective, of course, but they were calibrated to my tastes and helped me improve my shots. There is some variation in the scores. My aim was to be consistent for each metric, but some times the granularity was difficult.
Total Dissolved Solids (TDS) is measured using a refractometer, and this number combined with the output weight of the shot and the input weight of the coffee is used to determine the percentage of coffee extracted into the cup, called Extraction Yield (EY).
Shot Performance
For comparison, I pulled a shot without a cloth, one with shredded cloth, and one with cloth in the middle. There wasn’t much difference in taste, but EY was higher for cloth in the middle as the flow was better. The roast was two weeks old, so I could have waited another week.
All three shots had similar shot times, which was tied to the age of the roast because I had to do a long pre-infusion time.
The initial thought behind this experiment was to improve the process of using cloth filters. Cloth filters are the best addition to improve espresso shots, but they are difficult to manage over time. The first two shots with a cloth filter aren’t the best, but the next few shots are better. But the filter starts to shrink, which causes more donuting from side-channeling. If you could add shredded bits of cloth, maybe you could still reap the advantages of cloth more consistently. Maybe there is also a better way to do this than how I did it.
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Further readings of mine:
Collection of Espresso Articles
A Collection of Work and School Stories
A Summary of the Staccato Lifestyle
Measuring Coffee Grind Distribution
Espresso Baskets and Related Topics