Coffee Data Science
Wafo Spirit vs VST: Another Look at Espresso Baskets
A revision based on profile changes
Two years ago, I compared the Wafo Spirit espresso basket to the VST precision basket. The Wafo basket was new in design, material, and precision, and it came out when a few other similar baskets were being released. In a similar way that VST revolutionized the precision of the espresso basket, Wafo and others would seemed to do cause another espresso basket revolution.
I started my comparison, but it ended quickly (after 11 shot pairs) because all data pointed to the Wafo Spirit being superior. I was more interested in other variables for espresso, and additionally, the Wafo basket outperformed the Weber Unilever basket.
A lot has happened in two years with respect to how I understand espresso, and I began to be curious enough to redo the comparison between the Wafo and VST basket.
To my surprise, over 29 shot pairs, there was statistically no difference in performance. This suggests that while the Wafo basket improves espresso for certain profiles, when the profile is more optimal, the basket itself is less important of a variable.
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).
Shot Data
There was some noise in the shot pairs, but most were within a point of each other.
I broke this data down by general region of where the beans were from, and I did not find a particular preference of basket based on bean origin.
The average amongst the individual taste components was very close. Hold conclusions about the gap until we look at statistical tests.
For TDS/EY, performance had a similar trend compared to taste with one major outlier caused by a mistake in the shot being pulled.
In terms of statistical significance, no differences were statistically significant (p-value < 0.05) using a two-tailed paired t-test.
This result points towards individual optimizations helping to overcome other inefficiencies. This result also makes me want to question other variables in my profile to better understand what has become redundant in my routine.
I still use the Wafo Spirit as my main basket. This data helps explore how complex espresso is, and how data can be used to better understand real vs fancied impact.
If you like, follow me on Twitter, YouTube, and Instagram where I post videos of espresso shots on different machines and espresso related stuff. You can also find me on LinkedIn. You can also follow me on Medium and Subscribe.
Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
