Coffee Data Science

Optimizing Espresso on the Flair Signature

Signing a soon to be classic machine

5 min readOct 10, 2023

I got the Flair Signature in 2018, and I pulled a lot of shots. However, other machines seemed to be better and less time intensive. More importantly, I bought a few more machines, so my frequency of us on the Flair slowed.

However, I gave it another go when my first floor flooded. We had to go to a hotel, so I brought the Flair Signature with the Niche Zero with me. The key was applying the previous knowledge I had gained to maximize extraction yield.

I accomplished my goal with thermal pre-infusion and silicone rings.

Pre-Heat

Heating the grouphead has always been challenging. Steam is the most useful, but when traveling, I didn’t bring a kettle. I used water in the microwave.

I figured out that a Fellow travel mug was effective. I poured hot water into the mug, put the grouphead on top, and put at cap at the top.

This was very effective in warming up the grouphead. I used the same method with the portafilter locked in, which allowed me to do thermal pre-infusion.

Shower Screen Ring

I have found a restricted shower screen performs better, so I cut a silicone ring to sit beneath the shower screen.

I pulled a shot, and noticed a heavy dark ring. The dark spots went up the side a little meaning that the flow slowed down. I suspected this was partially do to the holes on the filter basket not going to the edge of the basket.

Bottom Silicone Rings

As a test, I cut two silicone rings for the bottom of the puck. I figured that if there isn’t much flow going to that ring, I should restrict coffee flow to the edge a little bit.

This is six frames from the video of the shot, and it looks splotchy, but the extraction was good. This basket and the other one for my machine have the same extraction pattern dictated by the hole size distribution.

In looking at the puck afterwards, there are dark spots down the side of the puck.

I cut it open, and I saw distinct traces of channeling. I suspect this is due to uneven holes in the filter basket, which I have previously looked at.

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 a few feasibility shots, and there could have been other variables at play. The taste saw a noticeable improvement.

In terms of TDS, EY, and IR, there was also an improvement.

At the very least, I feel more confident in making repeatable coffee when traveling using the Flair Signature.

Pre-heating is so important for good espresso, and I should also note I packed the basket to the top. Leaving little headspace has been key for syrupy, high TDS shots with excellent mouthfeel.

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.