A typical espresso machine pushes water at one set pressure from the start of a shot to the end. Pressure profiling changes it as the shot runs: gentle at first, full in the middle, easing off at the end. Lever machines have long done a version of this, and Rao calls the end of his model a “lever-style” decline.
This page assumes you can already pull a consistent flat shot. If not, start with our dial-in guide; profiling makes small inconsistencies bigger, not smaller.
Pressure and flow are two different controls
Pressure is how hard the machine pushes. Flow is how fast water actually passes through the puck. The puck’s resistance links the two, and that resistance changes during the shot.
- More pressure isn’t always more flow. Rao writes that flow rises with pressure until somewhere between 7 and 9 bar at the group head; beyond that, the extra pressure compacts the bed more than it pushes water through.
- Your gauge may not show the group. Rao notes that almost every built-in gauge reads pressure at the pump. Pressure at the group is a little lower, by an amount that varies from machine to machine.
- The puck wears as the shot runs. Rao explains that holding the pump pressure constant shows up as a slow fall in pressure at the group, because the bed resists less as it erodes. Decent, which makes a programmable machine, describes the same thing from the other side: hold the pressure fixed and the flow speeds up near the end of the shot.
That gives two ways to shape a shot. A pressure profile sets the pressure and lets the flow follow the puck. A flow profile sets the flow and lets the pressure follow; Decent notes that with flow capped, the pressure falls on its own as the puck breaks down. Decent’s guidance uses flow control for preinfusion, because a dry puck that is still soaking up water gives no meaningful pressure reading.
The two views overlap more than they differ. Holding the flow steady makes the pressure fall as the puck breaks down, which is the shape of Rao’s decline. Decent’s documentation adds that a flow that falls at the end of a shot tastes flat and muted to them, so how fast you let the pressure drop matters. Both are practitioners’ views, not settled findings.
Rao’s three-phase model
Rao set out this profile in Espresso Extraction (2013). He’s candid about its origins: he designed it before he had much experience with profiling machines, then suggested versions to consulting clients. None of them, he writes, claimed to have improved on it, and their experience taught him two things: the best shot times were longer with a ramp-up and a declining finish, and the profile allowed higher extraction than a flat one.
Rao’s preinfusion is a ramp, not a hold at a fixed low pressure: the curve climbs steeply from zero to full pressure over those first seconds. The decline is much gentler than the ramp.
Finding your machine’s full pressure
This applies only if your machine lets you set the pump pressure. Rao’s test finds the pressure that gives the most flow through your coffee, which he uses as the starting point for the full-pressure phase.
- Fit a blind filter and, with the pump running, set it to 7.5 bar on the machine’s gauge (7.0 bar if you measure at the group).
- Pull three shots with the same dose, weighed to 0.1 g, and the same prep. Stop each at exactly 30 seconds, weigh it, and average the three.
- Raise the pressure by 0.5 bar and repeat.
- When the average shot weight falls, stop. The best pressure is the one that gave the heaviest average.
- If you like, retest around it in smaller steps, such as 0.2 bar.
Don’t change the grind during the test, and throw out any shot that channels.
What profiling changes in your routine
- Dose to 0.1 g. Rao found that with a ramp-up and decline, raising the dose from 18.0 to 18.5 g can cut the shot weight by perhaps 3 to 4 g, so he recommends keeping every dose within 0.1 g of the target.
- Tamp the same way every time. Rao notes that tamping pressure changes the space above the puck, which delays full pressure and distorts the curve the machine is meant to follow. If several people share the machine, agree on one tamp.
- Grind finer. A gentle start needs a finer grind for the same flow; Rao sees that as one of preinfusion’s benefits.
- Expect longer shots. Rao’s time range for espresso is 25 to 40 seconds: flat profiles at the low end, profiling machines at the top. Our Brew Guide and Fix My Coffee time a flat shot at 25 to 30 seconds, so a profiled shot will run past their target without anything being wrong.
- Log every shot, with the profile you used. Our shot log works for this too: change one phase at a time and taste.
Preinfusion without a profiling machine
You can’t shape the whole curve without the hardware, but many machines can preinfuse. Rao’s rule of thumb in The Professional Barista’s Handbook is that low-pressure infusion followed by an uninterrupted rise in pressure is probably worth using. He describes four methods:
- Manual preinfusion. You start at low pressure and decide when full pressure begins; lever machines and some semi-automatics do this. For a machine fed at mains line pressure, his starting point is a line pressure of 3.5 to 4.5 bar (51 to 65 psi) and preinfusion times of 3 to 10 seconds.
- Progressive preinfusion. A spring-loaded chamber at the group lets the pressure on the coffee build gradually.
- Flow restriction. A small restrictor, or gicleur, slows the water to the group, delaying full pressure.
- Pulsed (electronic) preinfusion. The pump switches on and off in the first seconds. Rao found it doesn’t wet the bed properly and didn’t recommend it.
Your machine’s manual says which kind it has, if any. With any preinfusion, expect to grind a little finer for the same flow.
Which machines can profile
These examples show the main ways machines give you control during a shot, as published by the makers:
- Manual levers. Your arm sets the pressure. Flair describes its Flair 58 Plus 2 as a direct-lever manual machine with an integrated pressure gauge.
- Flow control at the group. Lelit describes the Bianca’s paddle as changing the water flow on the coffee until the highest pressure is reached, with a group gauge that reads the actual extraction pressure.
- Programmable machines. Decent’s DE1 lets you draw either a pressure curve or a flow curve on its tablet, and reports pressure at the puck.
- Fixed-pressure machines, with or without a preinfusion stage, can’t change the curve during a shot.
If your machine can’t profile, even distribution and a level tamp are what Rao relies on to prevent channeling; our channeling guide covers both.
Is it worth it?
Rao’s verdict on preinfusion was that it won’t necessarily make your best shot better, but it will almost certainly make great shots much more frequent. Profiling adds control, and it adds variables. If your shots are already consistent and you enjoy experimenting, it’s a rewarding next step; if they aren’t, puck prep and a steady dial-in will help more.
Sources
- Scott Rao, Espresso Extraction: Measurement and Mastery (2013), chapter 1 (“What Is an Ideal Extraction?,” the time range), chapter 3 (“Pump Pressure” and “How to Optimize Pump Pressure”) and chapter 11 (“Pressure Profiling,” including the model profile chart and “Quirks to Consider When Using Pressure Profiling”)
- Scott Rao, The Professional Barista’s Handbook (2008), pp. 27–30 (“Preinfusion,” “Why Preinfusion Works,” “Common Preinfusion Methods” and “Other Considerations”)
- Decent Espresso, “Pressure vs. flow profiling, and how to convert into an advanced shot” (documentation, updated July 2026) and “Decent Espresso Overview,” checked October 15, 2026: decentespresso.com/docs and decentespresso.com/overview
- Lelit, “Bianca PL162T-EU” product page, checked October 15, 2026: lelit.com
- Flair Espresso, “Flair 58 Plus 2” product page, checked October 15, 2026: flairespresso.com