Coffee Data Science
Tamp Pressure for Espresso
Exploring pressure affects on the shot
Espresso is by far the richest way but also the most difficult way to produce coffee. There is a challenge in every shots as multiple variables come together to form a beautiful thing. Grind setting, tamp pressure, water temperature, pressure, pre-infusion, dosage, basket, grinder, and machine all play a part. The most challenging obstacle, for a beginner, is being able to understand what adjustments they should make based on how other shots run.
I’ve been look at all the ways I do failure analysis for my espresso shots, and I thought it would be interesting to look at a couple of variables. At the beginning, I want to look at these variables separately and show what I see in the hopes that it will help someone else better see their shot output and understand where to go from there.
This article focuses on 3 tamp settings. For each one, I put the grounds in a basket, used a toothpick to distribute them, and used an automatic leveler to tamp. I made the center a little less dense to combat donuting inherent in lever machines. I also used the same basket and the same beans for all three shots. Then I tamp each one with a scale to measure the tamp pressure. I also tamp lightly compared to others, and previous data on tamp pressure reveals pressures beyond 5lbs (2.27 kg) decreases extraction yield.
I took videos for each shot. Every row is 5 seconds in time. The columns are 200g, 400g, and 600g of tamp pressure.
200g …….……………….400g …..…………………………….600g
The shots flowed pretty similarly. The flow logs don’t tell any special story except that the 600g shot flows a little slower.
The bottom of the puck for these shots also didn’t reveal anything particular except that the 400g shot was a little one sided. The 200g bottom has more dark spots throughout while the center of the 600g tamp has very few dark spots.
200g …….……………….400g …..…………………………….600g
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).
Taste and EY
As for taste, the 400g shot tasted the best. For TDS/EY, 600g performed the best, but it was pretty close to the 400g tamp.
In terms of time, the 600g tamp took the longest to cover the filter, and the infusion time was longer, but they were pretty similar.
The key to making good espresso is to experiment and try out some different tamp pressures. Try out a few different variables, and try to understand how to make adjustments until you get something that tastes of heaven. Then keep adjusting all your variables until you reach the next level of heaven as all these different variables are inter-connected.
If you like, follow me on Twitter and YouTube 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:
Collection of Espresso Articles
A Collection of Work and School Stories
Measuring Coffee Grind Particle Distribution using Image Processing
A Summary of the Staccato Lifestyle
Measuring Coffee Grind Distribution
Espresso Baskets and Related Topics
