What Is Pre-Infusion in Espresso?
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Watch a skilled barista on an E61 machine and you may see a small pause: the lever goes halfway up, nothing much happens for a few seconds, and then the shot begins. That pause is pre-infusion. What is pre-infusion in espresso? It is a short, low-pressure phase at the start of the shot in which water gently soaks the coffee puck before the full brewing pressure of around 9 bar kicks in. A wet, swollen puck resists water more evenly, which can reduce channeling and make extraction more uniform.
Below you will find how pre-infusion works on different machines, how long to use it, when it makes a real difference, and a simple test you can run at home.
Key takeaways
- Pre-infusion wets the puck at low pressure before full pressure, so water flows through it more evenly.
- Many baristas pre-infuse for about 2 to 8 seconds; programmable machines let you go longer.
- It helps most with light roasts and imperfect puck prep; with dark roasts, the difference is often small.
- Passive pre-infusion is built into E61 groups and lever machines; many entry-level machines have little or none.
- Change only one variable at a time and taste the results side by side.
In this article
- How pre-infusion works
- Types of pre-infusion by machine
- How long should pre-infusion be?
- When pre-infusion helps and when it does not
- A home test you can run
- FAQ
What is pre-infusion in espresso, and how does it work?
Dry ground coffee is not uniform. When water hits it at full pressure all at once, it can find the easiest routes through cracks, loose edges or less dense areas, a problem called channeling. Those paths over-extract while the rest of the puck is under-extracted, giving a shot that is sour and bitter at the same time.
Pre-infusion slows the start. Water arrives at low pressure, wets the grounds and lets them swell. As the bed expands, small gaps close and the puck becomes more uniform. When full pressure arrives, the water meets a bed that resists it more evenly. Fresh coffee also releases carbon dioxide on contact with water; giving that gas a moment to escape is related to the bloom you see in pour-over, explained in our article on the coffee bloom.
Types of pre-infusion by machine
| Type | Where you find it | How it works | Control |
|---|---|---|---|
| Passive chamber (E61) | Many heat exchanger and dual boiler machines | A small expansion chamber in the group, about 8 to 10 ml, fills first, delaying full pressure | Fixed and short; on plumbed machines you can also hold the lever halfway |
| Line pressure | Plumbed E61 machines and many commercial machines | Mains water pressure, far below 9 bar, soaks the puck before the pump starts | Manual (lever halfway) or programmed |
| Spring lever | Lever espresso machines | Water enters at boiler or line pressure before the spring engages | Set by how long you hold the lever |
| Programmed or pulsed | Many modern home machines, from Breville models to the La Marzocco Linea Mini | Electronics run the pump at low power, pulse it or pause it before full pressure | Adjustable time and sometimes pressure |
| Flow or pressure profiling | Profiling machines and paddle groups | Barista or software controls pressure or flow throughout the shot, including the start | Full control |
The E61 story
The E61 group, launched by Faema in 1961 and named, according to Swiss coffee educators Kaffeemacher, after the total solar eclipse visible in Italy that year, made passive pre-infusion common. Its cam-operated valves and small expansion chamber gently wet the puck before the pump reaches full pressure. Its thermosiphon loop also keeps the heavy brass group hot. More than six decades later, versions of the design remain among the most common groups on prosumer machines. For the bigger story, see who invented the espresso machine.
How long should pre-infusion be?
There is no single correct time, but practical ranges look like this:
| Roast and situation | Starting pre-infusion | Notes |
|---|---|---|
| Dark roast, good puck prep | 0 to 3 seconds | Dark roasts extract easily; long soaks can push them toward bitterness |
| Medium roast | 3 to 6 seconds | A good default on most machines |
| Light roast | 5 to 10 seconds or more | Dense beans benefit most from a thorough soak |
| Channeling problems | Add 2 to 3 seconds | Fix distribution too; pre-infusion is a helper, not a cure |
Many baristas on manual machines pre-infuse for about 2 to 8 seconds, and the right time depends on coffee, grind and machine. A useful sign on a bottomless portafilter: the first drops appear evenly across the basket rather than in one corner.
Does pre-infusion count in shot time?
Conventions vary. Some baristas start the clock when they press the button, others when the pump reaches full pressure. Either is fine as long as you are consistent. If you add pre-infusion, expect the total time to increase; judge the shot by taste and yield, not by a fixed number of seconds.
Will I need to change my grind?
Often, yes. A well-soaked puck can let water through more readily once full pressure arrives, so many people find they can grind a little finer with pre-infusion. Adjust in small steps and keep dose and yield the same while you test.
When pre-infusion helps and when it does not
- Helps most: light roasts, very fresh coffee, finer grinds, imperfect distribution and machines with aggressive pressure ramps.
- Helps a little: medium roasts with solid puck prep. Seattle Coffee Gear calls the gain real but modest in this case.
- Helps least: dark roasts, which extract easily; the difference is often hard to taste.
- Cannot fix: a poor grinder, stale beans or an uneven tamp. If shots are sour or bitter, start with our guide to under- vs over-extracted coffee.
If you are choosing a machine, pre-infusion is a nice feature but not a reason on its own to spend more. A good grinder will improve your espresso far more. Our guide to types of espresso machines helps you weigh the options.
A home test you can run
- Pick one coffee and one recipe, for example 18 g in, 36 g out.
- Pull a shot with no pre-infusion (or the shortest your machine allows).
- Pull a second shot with 5 seconds of pre-infusion, keeping dose, grind and yield the same.
- Pull a third with 10 seconds.
- Taste them side by side, ideally blind. Note sweetness, sourness, bitterness and texture.
Run the test with a light roast and a dark roast to feel the difference. A bright coffee such as our Ethiopia Natural, a medium-light Sidama roast with milk chocolate, ripe fruit and caramel, shows pre-infusion’s effect clearly. Compare it with our Italian Roast, our darkest blend, where you may find little change. Kenya from Nyeri, bright and juicy with citrus and floral notes, is another great test for light-roast technique. All are roasted 1 to 5 days before delivery; browse our single origins for more.
Pre-infusion FAQ
Is pre-infusion the same as blooming?
They are related. Both wet the coffee before the main extraction. In espresso, blooming usually refers to a longer pause after pre-infusion before ramping up pressure.
Does pre-infusion make espresso less bitter?
It can, if bitterness comes from channeling. By wetting the puck evenly, it reduces over-extracted channels. It will not fix bitterness from a very dark roast or an over-long shot.
Do all espresso machines have pre-infusion?
No. Many entry-level machines ramp straight to full pressure. E61 machines, lever machines and many mid-range and high-end machines include some form of pre-infusion.
What pressure is used for pre-infusion?
Low pressure, typically line pressure or a few bar, well below the roughly 9 bar of normal extraction.
Can you pre-infuse too long?
Yes. Very long soaks on dark or very fresh coffee can lead to over-extraction or uneven flow. Increase time in small steps and stop when taste stops improving.
Sources
- What Is Pre-Infusion and Does It Matter?, Seattle Coffee Gear
- What Is Pre-Infusion?, Clive Coffee
- Faema E61 brew group, Kaffeemacher
Facts checked in October 2026.
Keep reading: How to make espresso at home · Types of espresso machines · Shop single origins