A spring lever espresso machine's inherent pressure profile is a natural curve,
starting with a gentle pre-infusion and quickly ramping up to a peak pressure before tapering off
as the spring expands.
Skilled baristas can manipulate this profile by "pulling back" or "pushing through" the lever to control flow, enhance specific flavors, and achieve greater extraction uniformity compared to conventional, fixed-pressure machines.
The Basic Spring Lever Profile
1. Pre-infusion:
The process begins with a gentle pre-infusion, using lower pressure (around 1.5-5 bar) to saturate the coffee grounds.
2. Pressure Ramp:
Releasing the lever allows the compressed spring to expand, creating a quick spike in pressure (around 9-12 bar).
3. Pressure Taper:
As the spring continues to expand throughout the shot, it exerts less force, causing the pressure to gradually decline.
Note, there is a variation of this spring lever profile called "Londinium profile".
It is a adapted version of the spring lever profile that uses
a higher initial pre infusion pressure. For more info:
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There are two types of spring lever machines:
Single vs Dual.
Single spring.
This is a Elektra La Casa.
The spring produces about 8 bar pressure
This pic is from the Decent app
The Elektra is a really simple single spring machine, but it gives me some of the best tasting coffee I've ever had. The temp is closer to 90C, and I think the pressure lives somewhere between 7-8 bar.
Examples of dual spring lever espresso machines are the ACS Vostok and the Nurri Leva. They feature a double spring system for a consistent and repeatable extraction pressure.
These machines incorporate a lever system with an inner and outer spring to provide a controlled and gradual pressure release, offering users precise control over the brewing process.
How it works:
Double Spring System:
Unlike single spring designs, a dual spring system in a lever machine uses two springs—an outer and an inner—to create a more stable and controllable pressure profile during the extraction.
Lever Operation:
When the user pulls the lever, it compresses the springs, which then provide a consistent, descending pressure to the coffee puck.
Consistency:
The dual spring setup helps to minimize pressure fluctuations, leading to a more repeatable and high-quality extraction.
Examples of machines:
ACS Vostok:
This machine is known for its use of a double spring system in its Lost Marco-clone group head, allowing for a repeatable style of extraction.
Nurri Leva SA:
Another example of a modern dual spring lever machine, the Nurri Leva is praised for its beautiful design and innovative features, including the dual spring mechanism
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These are some graphs using the Smart espresso pressure profiler app
Pressure reaches 0.5 bar at 1 secs.
Stays there till 11sec. then steep ramp up.
Pressure hits 6.5 bar at about 17 secs followed with a gradual decline in pressure over 45 secs
Profitec dual spring
Pressure reaches 0.75 bar at 1 secs.
Stays there till 11sec. then steep ramp up.
Pressure hits 9 bar at about 18 secs followed with a gradual decline in pressure over 35 secs
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Faemia Faemia 1964
Its a pretty old machine .
The highest pressure is I think about 5 bar. The coffee isn't perfect, but this machine is more sculpture and work of art.
Really long 20 sec preinfusion that initially rises to 1-2 bar then settles down to 1 bar.
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For fun I though I'd add a La Marzocco Leva x (graph below)
The X is a springless machine.
It utilizes a sophisticated electro-pneumatic system for brewing and pressure control rather than mechanical springs.
Pressure reaches 2.5 bar at 3 secs.
Stays there till 10sec. then steep ramp up.
Pressure hits 9bar at about 13 secs followed with a gradual decline in pressure over 50 secs
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