The Kim Max filter has almost twice the surface area of the holes than the VST filter, and the average hole size is not only larger, but also more widely spaced.
Then I took out a glass.
Coffee Maker: A decent coffee maker
Coffee grinder: Zero niche
Coffee: Home Roasted Coffeemedium (First crack + 1 minute)
Shot Preparation: Staccato Tamped
Preinfusion: long, ~25 seconds
Filter basket: 20g VST and Imprecision basket.
Other equipment: Atago TDS meter, Acaia Pyxis scale
To evaluate the differences between techniques I used two sets of metrics: Final Score and Coffee Extraction.
Final result is the average of a scorecard of 7 metrics (acute, opulent, syrupy, sweet, sour, bitter, and aftertaste). These ratings were of course subjective, but they were calibrated to my tastes and helped me refine my shots. There is some variation in the results. My goal was to be consistent across each metric, but sometimes the granularity was complex.
Total Dissolved Solids (TDS) is measured using a refractometer and this number, combined with the output weight and input weight of the coffee, is used to determine the percentage of coffee in the cup, called Extraction Efficiency (EY).
Intensity Radius (IR) is defined as the radius from the origin on the control chart for TDS vs EY, so IR = sqrt( TDS² + EY²). This metric helps normalize shot efficiency across the entire output efficiency or brewing ratio.
Let’s start with two pairs of shots. I took them during the cooling extraction study, so I have with and without. As for taste, Kim D Max came out noticeably better. As for TDS and EY, it’s a mix.
