Observations of Line Pressure vs Boiler Pressure on my Londinium R

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#1: Post by cskorton »

Hi All!

I've found some pretty interesting differences in taste when comparing the same coffee at the same grind setting at different preinfusion pressures of 1.5 bar vs 3 bar on my Londinium R.

There's been a lot of talk about the superiority of using line pressure (usually around 3 bar) over boiler pressure of a typical dipper (around 1.3 bar). In practice, however, I've found that generalization to not always be true and has left me somewhat confused. I'm hoping to get your thoughts as well.

Paradise Coffee Roasters Philippines Gloria Estate. Bag states it's dark roast but I'd consider it more medium (I consider something like Saka to be true dark roast).

Tasting notes stated on the bag are Lime, Cola, and Toasted Marshmallow

1.5 bars of pressure:
For my first shot I used lower preinfusion pressure in accordance to Reiss's advice. In theory, shots pulled in this way are at a lower temperature. Starting pressure after pulling the lever up is around 7 bar, ending around 5 bar (I think).

I preinfused for 10 seconds, until I could visually see water peeking through the bottom of the ports filter. I slowly raised the lever and let the shot run for a total of 28 seconds. 16g in, 30 grams out.

Visually, the shot was somewhat ugly and I could tell the extraction was somewhat uneven. At 1.5 bars of pressure, the water struggled to fully saturate the puck.

Taste wise, it was excellent. I'd describe it as soft and sweet. All of the tasting notes on the bag clearly came through, though I had to really search deep for that toasted marshmallow note at the finish. Body was light and airy, almost like a soufflé.

3 bars of pressure:
I kept the grind exactly the same, which is out of the ordinary. I always use a slightly finer grind setting at 3 bar, but figured I'd compensate with a shorter preinfusion time. In theory, at 3 bars of pressure the water temperature will be higher and peak pressure will be higher at 8 bar, dropping to 6 bar before finishing the shot.

Preinfusion time was 6 seconds before I saw coffee evenly peeking out from the bottom of the portafilter. Shot ran for a total of 28 seconds. 16g in, 31 grams out.

Visually, it was stunning and much better looking than the 1.5 bar shot. The extraction was much more even for sure as the water was evenly pressed through the puck at 3 bar.

Interestingly, I'd describe the taste as harsher than the 1.5 bar shot. Each tasting note was sharper, with the biggest difference being in the finish. It didn't have that delicate aftertaste and I'd describe it as somewhat astringent and not as pleasant. Body was heavier, which I preferred.

Follow up:
Have you all experienced the same? I'm surprised that visually a shot can look so good yet taste not as great. What do you think is the driving factor since grind setting was the same? Do you think it was differences in temperature or pressure? I believe flow was kept about the same but there's no way for me to know for sure.

Reiss's suggestions for changing preinfusion pressure are as follows:
1.5 bar - dark roast
2-2.5 bar - medium roast
3+ bar - light roasts


#2: Post by mathof »

I sometimes wonder if bottomless portafilters have encouraged us to misjudge what's going on during an extraction. For example, I have often found that shots which show bare patches on the bottom of the basket taste fine and measure respectable TDS/EY. And conversely, as you point out, beautiful pulls are no guarantee of a good tasting shot. My conclusion is that more goes on inside the puck than is dreamed of in our theories.

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#3: Post by spressomon »

Generally, but not universally (jives with all things espresso making...), the longer the PI for medium-light and light roast level beans, the sweeter the espresso. But it comes at a cost: Flavor layers are more compressed. I have made some super tasty espresso on my Slayer, with 25 second +/- PI/PB to first drops on harder & lighter roasts.

I just finished a gift bag of "Santa's Helper" from Keith & Jen at Northbound and would classify it as dark side of medium roast. These were relatively hard beans...I was able to grind finer and extend the PI/PB time out to 22-25 seconds (unusual for this roast color based upon my experience) and pull a shot with the same general perimeters as I would for a lighter roast. And the espresso was not only sweet but had distinct flavor profile layers.

Bottom line: It all depends. :lol: Its great to have different "tools in the toolbox" to achieve what we desire in the cup.
No Espresso = Depresso