Coffee Data Science
Wafo Soe Classic vs VST for Espresso
Intenso espresso
Wafo has produced four new espresso baskets in 2022 that began wider sales in 2023. The basket designs are much different than previous espresso baskets, and they have a very interesting potential to change how espresso is brewed. I looked at the Wafo Soe Spirit, and now, I will write about the Soe Classic.
The Classic has a hole count around 4 times that of the VST. I have previously theorized that having more or larger holes would be beneficial to espresso because I (as have others) have observed stains between filter holes on the puck after the shot. This indicates that some solubles are getting stuck.
However, we need some data to better understand.
Equipment/Technique
Espresso Machine: Decent Espresso Machine and the Kim Express
Coffee Grinder: Niche Zero and the Rok
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Shot Preparation: Staccato Tamped
Pre-infusion: Long, ~25 seconds
Filter Basket: 20g VST and 20g Wafo Soe Classic
Other Equipment: Atago TDS Meter, Acaia Pyxis Scale, DiFluid R2 TDS Meter
Metrics of Performance
I used two sets of 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).
Intensity Radius (IR) is defined as the radius from the origin on a control chart for TDS vs EY, so IR = sqrt( TDS² + EY²). This metric helps normalize shot performance across output yield or brew ratio.
Data
I pulled 19 paired shots, and I stopped because the Wafo Soe Spirit arrived. I wonder if my shots are optimized to the point where such a change would not be as noticeable.
I didn’t see a big change in terms of extraction yield. Taste seemed like there were some improvements, but it was case dependent.
Even looking at IR, both baskets behaved similarly.
Broken down by machine, the Kim Express does not see a benefit, but in taste, the Decent does.
There wasn’t anything noticeable in the time metrics to distinguish both baskets.
The average scores don’t show much of a difference, and the average differences aren’t statistically significant when doing a two tailed paired t-test.
Here are the general statistics:
This initial data suggests there is something interesting with Wafo. More investigation needs to be done especially for people pulling longer shots on different machines.
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