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Easy Blooming: What ending preinfusion at a target pressure (dynamic bloom) and a pressure decline during extraction do to coffee
1. Introduction
This article is based on Stéphane Ribes' September 2020 Easy Blooming study, conducted on the Decent Espresso DE1PRO v1.1. The work investigates whether the conventional blooming-espresso approach can be made more tolerant of changes in grind size by replacing a bloom of predetermined duration with a dynamic bloom stage that ends when puck pressure reaches a defined threshold.
In a conventional blooming profile, the bloom lasts for a fixed period regardless of the hydraulic resistance of the coffee puck. If the grind is changed, however, water penetration and pressure development also change. Ribes therefore tested a pressure-triggered alternative: instead of ending the bloom after a fixed number of seconds, the machine advances to the next stage when measured pressure reaches a specified value.
The underlying hypothesis is that the bloom duration should adapt automatically to puck resistance. A coarser grind, which offers less resistance, should reach the pressure threshold sooner and therefore receive a shorter bloom. A finer grind should reach the threshold later and consequently receive a longer bloom.
The presentation states that this behavior makes extraction pressure less sensitive to grind variation and that espresso prepared at the most extreme grind settings was more enjoyable when the dynamic bloom was used.
The study then extends the concept further by combining dynamic blooming with pressure-priority extraction and a dynamic pressure decline. In this configuration, the rate of pressure decline changes according to the evolution of water flow, with the intention of stabilizing flow during the latter part of the extraction.
2. Questions asked
The experiments address six principal questions:
1. Can a pressure-triggered dynamic bloom make espresso extraction less sensitive to changes in grind size than a fixed-duration bloom?
2. How does dynamic blooming affect bloom duration, total shot time, pre-extraction drippage, extraction pressure, extraction yield, and sensory quality?
3. Does dynamic blooming improve espresso at the coarse and fine extremes of the tested grind range?**
4. **How does the behavior of dynamic blooming change when the post-bloom flow ramp is fast versus slow?
5. Can a pressure-priority extraction with dynamic pressure decline further widen the range of grind settings that produce enjoyable espresso?
6. Does dynamic pressure decline produce a more consistent flow rate during the final part of the extraction?
3. Method
Equipment and preparation protocol
The general test protocol used a Decent Espresso DE1PRO v1.1, a Mahlkönig EK43 S grinder fitted with SSP High Uniformity burrs with Silver Knight coating, and Montcalm water adjusted to 35 ppm CaCO₃-equivalent alkalinity and 112 ppm CaCO₃-equivalent total hardness using sodium carbonate and Epsom salts.
The portafilter and basket were preheated to 80°C in a kettle. Before every extraction, the basket and shower screen were dried completely with a clean tissue. Frozen beans were single-dosed and ground into a double-walled stainless-steel cup.
Puck preparation consisted of WDT in the basket using a homemade tool with three 0.4 mm needles and a Decent funnel, followed by gentle vertical taps. A Bravo Tamper, 58.50 mm in diameter, set to 36 lb, was used for tamping. For the tests performed on 19 September, a Hog puck-preparation tool with 0.8 mm needles was inserted and withdrawn vertically using a stand to ensure straight movement.
TDS measurements were performed with an Atago PAL refractometer, zeroed with the adjusted Montcalm water. Samples were not filtered and were measured at room temperature after vigorous stirring. Each reported data point represents the mean of three to five measurements.
Experiment 1: fast flow rise
The first experiment was conducted on 12 September 2020 using naturally processed Guatemalan coffee. The recipe was:
The profile used is called Easy Blooming. In the first round of the experiment, a 30-second fixed bloom was used followed by a 5-second ramp to 2.2 mL/s. In the second round of the experiment, the bloom ended when pressure reached 1.5 bar (dynamic bloom), followed by the same 5-second ramp to 2.2 mL/s.
Here's the settings for the 30-second fixed bloom step:
And here's the settings for the "Move on if...pressure is under 1.5 bar" (dynamic bloom) step:
Experiment 2: slow flow rise
The second test used the same coffee, dose, basket, output, shower screen, and grind range, but extended the post-bloom ramp to 12 seconds (vs. the 5 seconds in experiment 1).
The presentation contains one labeling inconsistency that should not be silently resolved: page 8 identifies the fixed comparator as a 20-second bloom, while page 9 identifies it as a 30-second bloom. Both slides specify a 12-second flow ramp to 2.2 mL/s. As in experiment 1, the first round of the experiment with a fixed bloom was followed by a dynamic bloom, which ended when pressure reached 1.2 bar.
Experiment 3: pressure-priority extraction with dynamic decline
A separate experiment was conducted on 19 September 2020 with anaerobically fermented Costa Rican coffee:
Both profiles used a dynamic bloom ending at 1.5 bar. The flow-priority comparator then used a 5-second ramp to 2.2 mL/s, whereas the alternative moved into a 6-bar pressure-priority extraction with dynamic pressure decline.
The presentation illustrates dynamic decline rates of approximately −0.2 bar/s, −0.1 bar/s, and −0.04 bar/s. A faster increase in water flow results in a steeper pressure decline.
4. Proceeding
For the flow-priority experiments, each profile was repeated across a sequence of six EK43 grind settings. The fixed-bloom profile was used as the reference, while the dynamic version replaced the time-based bloom termination with a pressure threshold.
The effect of the profile was then evaluated through:
The essential adaptive behavior can already be seen in the summary slide. With the same pressure-triggered bloom, the coarse EK1.9 grind receives an approximately 20-second bloom, whereas the fine EK1.4 grind receives an approximately 40-second bloom. A fixed-duration profile gives both grinds the same 30-second bloom.
The pressure-priority experiment subsequently examined whether dynamic blooming could be combined with an extraction whose pressure declines in response to flow behavior. The purpose was not simply to reduce pressure, but to make late-shot flow more uniform across grind settings.
5. Results
5.1. Fast flow rise
The fast-ramp experiment shows a clear difference in how shot duration responds to grind resistance. With the fixed bloom, total shot time remains relatively stable at roughly 57–60 seconds across most of the grind range. With dynamic blooming, coarse-grind shots become much shorter—approximately 46–47 seconds at EK1.9–EK1.8—while fine-grind shots become substantially longer, reaching roughly 68 seconds at EK1.5 and 73 seconds at EK1.4.
These values are approximate visual readings from the graph on the right, in which "Quick flow rise" is the shots with fixed bloom and the "Easy quick" line represents the shots with the dynamic bloom:
This is expected from the control logic: coarse pucks reach the 1.5-bar trigger rapidly, whereas finer pucks remain in the bloom stage for longer.
Extraction yield
Extraction yield remains comparatively insensitive to the bloom strategy. Both profiles cover roughly 22–25% EY, with the highest values at the coarser end and progressively lower yields toward EK1.4.
Approximate values from the graph are:
Thus, dynamic blooming does not materially increase EY across the entire range, although it appears to preserve slightly more extraction at the fine end.
Drippage before extraction
At coarse settings, dynamic blooming markedly reduces the beverage mass released before the main extraction stage. At EK1.9, the fixed bloom produces roughly 7.5–7.7 g of early drippage compared with approximately 5.8 g under dynamic bloom.
The relationship reverses toward the fine end. At EK1.4, the fixed profile produces less than approximately 1 g, whereas the dynamic profile produces around 3 g. Dynamic blooming therefore redistributes bloom duration according to puck resistance rather than minimizing drippage uniformly.
The graph showing the results is on the right-hand side. Again, in this context, "Quick flow rise" stands for the fixed bloom shot whereas "Easy quick" stands for the dynamic bloom shot.
Extraction pressure
The largest pressure peaks occur at the fine end of the grind range. Around EK1.5–EK1.4, peak extraction pressure approaches approximately 12–13 bar under the fixed profile. Dynamic bloom lowers these extreme peaks modestly, to approximately 11–12 bar.
To the right is the graph showing the extraction pressure results. Again, what's labelled "Quick flow rise" stands for the shot with fixed bloom, whereas "Easy quick" is the shot with dynamic bloom.
The difference is relatively small in the middle and coarse parts of the range, but it supports the presentation's central claim that extraction pressure becomes somewhat less sensitive to grind variation.
Sensory results with fast flow rise
The sensory graphs show the clearest advantage of dynamic blooming not at the optimum grind, but toward the edges of the grind range.
Both profiles produce their highest taste score around EK1.7, at approximately 8/10. At that grind, the two profiles are essentially equivalent.
At more extreme settings, however, the dynamic profile performs better:
Dynamic blooming also keeps sweetness relatively stable at approximately 3/5 across the range, whereas the reference profile falls to about 2/5 at several settings. Flavor clarity is likewise more stable, particularly around EK1.5. Astringency remains broadly comparable and does not show an obvious penalty from dynamic blooming.
Here's the taste scores of the coffee. As stated before, in our context, "Quick flow rise" is the fixed bloom shots, whereas "Easy quick" is the dynamic bloom shots:
The cup photographs are consistent with the quantitative results in showing usable espresso throughout the tested range, but the study's principal distinction is sensory rather than simply visual.
5.2. Slow flow rise
The slower 12-second ramp produces the same general adaptive behavior but with somewhat different hydraulic effects.
With a fixed bloom duration, total shot time of Easy Blooming is approximately 50–53 seconds across all grind sizes. With dynamic bloom (namely moving on once pressure reaches 1.5 bar) shot times vary much more widely: roughly 39–40 seconds at EK1.9–EK1.8, approximately 44–49 seconds in the middle, and approximately 56–61 seconds at EK1.5–EK1.4.
To the right is the graph showing the results. The shots with fixed bloom are labelled "Slow flow rise" whereas "Easy slow" stands for the dynamic bloom shots.
Extraction yield
Again, EY changes little between the two strategies.
Approximate values are:
The two profiles therefore produce broadly similar extraction yields despite substantially different bloom durations.
Drippage before extraction
Dynamic bloom has a large effect at coarse settings:
By EK1.7, the values converge near 2 g. At finer settings, the fixed bloom approaches virtually zero drippage, whereas the dynamic profile retains roughly 1 g.
To the right is the graph showing the results. Again, "Slow flow rise" stands for the fixed bloom shots whereas "Easy slow" stands for the dynamic bloom shots.
Pressure peak
Peak pressure rises sharply as the grind becomes finer.
At approximately EK1.5, the shot with fixed bloom reaches nearly 12 bar, while the dynamic bloom shot is closer to 10 bar. At EK1.4, both remain very high, but the dynamic bloom shot is still approximately one bar lower.
To the right-hand side is the graph showing the results. As before, the "Slow flow rise" stands for the fixed bloom shots whereas "Easy slow" stands for the dynamic bloom shots.
Thus, the pressure-triggered bloom again moderates, rather than eliminates, the increase in peak pressure caused by a much finer grind.
Sensory results with slow flow rise
The sensory data again indicate that dynamic blooming is most useful at the boundaries of the grind range.
The approximate overall taste scores are:
The improvement at EK1.4 is particularly notable. The fixed-bloom shot receives a very low score, while the dynamic version remains substantially more acceptable.
Dynamic bloom also preserves flavor clarity at the finest grind. The reference profile falls from approximately 3/5 to 1/5 at EK1.4, whereas the dynamic profile remains near 3/5. Bitterness at the fine extreme is also slightly lower, approximately 3/5 rather than 4/5. Sweetness and mouthfeel are generally equal or slightly better with dynamic bloom.
Here's all the results from the sensory analysis:
These results directly support Ribes' summary that the most extreme grind settings were more enjoyable when the bloom duration was pressure-triggered rather than fixed.
As in the previous experiment, the coffees looked fine from a visual perspective. However, what really matters when drinking coffee is that it tastes well:
5.3. Pressure-priority extraction with dynamic pressure decline
The final experiment extends the concept from bloom control into the extraction itself.
Both profiles begin with a bloom ending at 1.5 bar. In the first round of experiments, flow then ramps up to 2.2 mL/s over five seconds and is held constant. The alternative enters a 6-bar pressure-priority phase whose pressure declines dynamically.
Extraction yield is very similar between the two methods, remaining approximately 22.5–23.5% throughout the EK2.1–EK1.6 range.
There is no consistent EY advantage for either strategy.
Sensory consistency, however, improves with pressure decline.
Approximate taste scores are:
Here's all the results from the sensory analysis. The "Easy quick flow" stands for the shots with fixed flow and the "pressure decline" speaks for itself:
The conventional flow-priority version reaches a slightly higher peak score at EK1.9, but its performance deteriorates rapidly toward the finest grind. In contrast, the dynamic-decline profile remains relatively stable.
The same pattern appears in other sensory variables. Mouthfeel with dynamic pressure decline remains near 2–3/5 rather than dropping to approximately 1/5 at coarse settings. Flavor clarity remains close to 3/5 throughout the entire range, whereas the flow-priority profile rises to approximately 4/5 around EK1.8 before collapsing toward roughly 1/5 at EK1.6. Bitterness and astringency remain restrained.
The presentation therefore concludes that combining dynamic bloom with pressure-priority extraction further widens the usable grind range and that dynamically increasing the pressure-decline rate as flow rises produces more consistent flow late in the extraction.
6. Conclusion
Taken together, the experiments indicate that “Easy Blooming” is primarily a robustness strategy rather than a mechanism for substantially increasing extraction yield. A pressure-triggered bloom allows the profile to adapt its duration to puck resistance, reducing sensitivity to grind-size variation and improving sensory performance when the grind is considerably coarser or finer than the apparent optimum. The subsequent addition of dynamic pressure decline extends that principle into the extraction phase and improves consistency across an even broader grind range.
1. Can a pressure-triggered dynamic bloom make extraction less sensitive to grind size than a fixed-duration bloom?
2. How does dynamic blooming affect bloom duration, shot time, drippage, pressure, extraction yield, and sensory quality?
3. Does dynamic blooming improve espresso at the coarse and fine extremes?
4. How does the behavior differ between fast and slow post-bloom flow rises?
5. Can pressure-priority extraction with dynamic pressure decline further widen the usable grind range?
6. Does dynamic pressure decline make the final extraction flow more consistent?
#research #Ribes #coffee #preinfusion #dynamic #bloom #decline #documentation
mirjam created 2026/08/23, mirjam updated 2026/09/22