E61: The secret behind the chrome cylinder head - Deep Dive

Deep Dive E61: The Secret Behind the Chrome Head

You've opted for a machine with an E61 brew group – perhaps an ECM, Rocket, or Lelit? Then a piece of espresso history stands in your kitchen. The E61 was developed in 1961 by Ernesto Valente for the Italian manufacturer Faema and fundamentally changed the way espresso is brewed.

But why does this chrome-plated head weigh almost 5 kilos? Why does it take so long to be ready for use? And what exactly happens when you pull the lever? At the Coffee Coaching Club in Bern and Zurich, we explain the mechanics so you can feel them with your next shot.

Act 1: The Preparation – The Thermosiphon

Before you even think about coffee, the E61 is already working. The secret to its legendary temperature stability is the sheer mass of chrome-plated metal – and an ingenious, purely physical circulation system.

The brew group is connected to the hot boiler by two copper tubes:

1. Ascent: Hot water rises from the boiler through the upper tube into the hollow head of the brew group. Hot water is less dense than cool water – it rises naturally.
2. Heat Transfer: In the brew head, the water transfers its heat to the massive brass construction. This takes time – hence the 20 to 30 minutes warm-up phase until the entire head reaches operating temperature.
3. Return: The slightly cooled water becomes denser and heavier. It sinks through the lower tube back into the boiler, where it is reheated. This cycle runs continuously as long as the machine is on.

Act 2: The Shot Starts – The Cam Controls Everything

You pull the lever. What looks like a simple movement from the outside is a precise mechanical interplay on the inside. The central component: the eccentric shaft (cam).

The cam is a metal rod with an asymmetrical profile – not a uniform curve, but deliberate elevations. When you turn the lever, this shaft rotates, and its elevations push various valves open or closed. A single lever thus controls the entire water flow: inlet, pre-infusion, and pressure release.

Interactive: Pull lever, change pressure & temperature, pause/play. Explained in detail in the Coffee Knowledge article on the E61 brew group.

Lever all the way up: Pump starts

1. You fully pull the lever. A microswitch behind the lever activates the pump.
2. At the same time, the cam pushes open the upper inlet valve.
3. The hot water from the thermosiphon circuit flows with pump pressure into the center of the brew group – through a small nozzle element (gicleur), which already slightly restricts the flow – and then towards the coffee puck.

Act 3: The Core – Mechanical Pre-infusion

This is where the taste is decided. This is why E61 espresso has that characteristic soft, full-bodied character.

If the full 9 bars of pump pressure were to hit the dry coffee grounds immediately, cracks would form in the puck (channeling) – and the espresso would be thin and unevenly extracted. The E61 prevents this with a built-in "soft-start automatic" that works purely mechanically.

The detour of the water:

1. The water flows not only to the coffee but also simultaneously into a small, hidden chamber in the lower part of the brew group – the pre-infusion chamber.
2. This chamber is sealed by a spring-loaded valve. As soon as the pressure in the brew head reaches approximately 1.5 to 4 bars (depending on the spring design), this valve opens, and the water fills the chamber.
3. This is the crucial mechanism: As long as this chamber is filling and the spring resists, the pressure on the coffee grounds builds up slowly. The coffee grounds are gently moistened, swell up, and "repair" small irregularities in the puck.
4. Only when the chamber is completely filled can the pressure rise to the full 9 bars. The actual extraction under full pressure begins.

All of this happens purely mechanically in the first 4 to 8 seconds of your shot. You often hear it because the pump works a little quieter at the beginning and then audibly "engages."

The Finale: Lever Back – Pressure Release

Your espresso is ready, you pull the lever back.

1. The pump stops (microswitch triggers).
2. The cam rotates back. The upper inlet valve closes immediately – no new water flows in.
3. At the same time, the cam pushes open the lower outlet valve (pressure relief valve).
4. The residual pressure still in the portafilter above the coffee puck escapes downwards into the drip tray. That typical hiss you hear.

This ensures that you can safely remove the portafilter immediately. The coffee puck is relatively dry – no hot splashes when removing.

All E61 Features at a Glance

• Massive brew head made of chrome-plated brass (approx. 4 – 5 kg)
• Thermosiphon circuit for passive temperature stability
• Mechanical pre-infusion via spring-loaded chamber
• Cam control: One lever controls all valves
• Pressure release when turned off – clean puck, safe removal
• Purely mechanical system – no electronics in the water path
• Standardized 58mm mount – compatible with a wide range of accessories
• Proven technology since 1961 (patent by Ernesto Valente, Faema)

E61 Brew Group: Technical Overview

Who is an E61 machine suitable for?

The E61 is the right tool if you are looking for the classic, full-bodied espresso. Round, viscous, with deep body and chocolate notes. If you celebrate the ritual – pulling the lever, feeling the mechanical feedback, hearing the hiss of pressure release. And if you're willing to plan 20 minutes of warm-up time in the morning (or use a timer).

In combination with a high-quality coffee grinder and our roasts like Cozy Chocolate or Nutty Delight, the E61 fully plays to its strengths: the gentle pressure build-up precisely emphasizes the chocolatey, nutty notes that characterize these roasts.

Do you need more temperature precision, shorter heat-up times, or electronic control? Then take a look at our machines with saturated brew groups (La Marzocco) or the Arkel Coast – different philosophy, different result.

Experience E61 Machines at the Coffee Coaching Club

In our showrooms in Bern (Gerberngasse 44) and Zurich (Hagenholzstrasse 50b), you can see E61 machines from ECM, Rocket, Lelit, and other manufacturers live. Pull the lever yourself, feel the mechanics, compare the espresso with that of a La Marzocco Micra. When purchasing a coffee machine priced at 1500 CHF or more, you receive a free 60-minute barista workshop with us – so your first shot at home is perfect.

Frequently Asked Questions about the E61 Brew Group

The massive brass head (4 – 5 kg) must fully reach operating temperature. This takes 20 to 30 minutes. The advantage: once hot, the E61 maintains an extremely stable temperature – even with several shots in a row. Many owners use a timer so that the machine preheats automatically in the morning.

Yes. The mechanical pre-infusion generously forgives minor errors in tamping and grind size. The gentle pressure build-up compensates for slight irregularities in the puck. This makes the E61 a forgiving platform – especially if you are still fine-tuning your workflow.

A good espresso grinder is crucial for any portafilter machine. For E61 machines, we recommend at least a solid single-dose grinder. Depending on your budget, the Varia VS4, the Option-O Lagom, or a Weber Workshops grinder are ideal partners.

Neither nor – it depends on your priorities. The E61 delivers a softer, rounder espresso with more body and is more forgiving of errors. The saturated brew group offers higher temperature precision, faster heating time, and clearer flavor separation. The best option is to visit our showrooms and compare both directly in the cup.

Roastery Tip

The E61 is perfect for medium to darker roasts. Its gentle pressure build-up emphasizes body, sweetness, and chocolate – precisely the strengths of our Cozy Chocolate and Nutty Delight. For nutty depth, Very Nutty on an E61 is particularly impressive. If you also want to try light, fruity roasts: the E61 can do it, but a machine with a saturated brew group will bring out the delicate fruit notes even more clearly.