|
Lever machines are becoming more popular for home use where more control of the pressure and extraction really pays off.
Home lever models such as the Olympia cremina lever, LaPavoni Euro piccola lever, Bezzera Strega lever, Nurri Leva, ACS Vesuvius, Profitec pro 800, Marzocco Leva X 1, Fracino Retro, Londoninium, Ponte Vecchio Lusso Lever 1 Group, Quick Mill Achille, Izzo Alex Leva are becoming ever more popular in the home. Commercial lever machines such as Bosco, Astoria Core 600, Izzo Pompeii, ACS Vostok, and Victoria Arduino 358 White Eagle Leva, Vibiemme REPLICA Manuale PISTONE are all used in busy environments.
While they don't require a lot of maintenance - you cannot neglect changing the pistons gaskets or shower screens.Cafelat piston lever gasket and Cafelat Lever Gasket cover most modern lever pistons - a little Molykote 111 grease is needed to ensure smooth operation. Most modern levers now use the E61 shower screens IMS Competition Nano Shower Screen E61200NT is a popular choice as it requires almost no cleaning.
Q. What makes the lever so special?
- The long preinfusion: Pull the handle down - the water fills the group head for a low-pressure infusion, for about 10 seconds, then lift the lever,11 bars of pressure are released and the pressure drops down to around 5 bars by the time the shot is finished.
- The extra preinfusion and 11 bar of extraction allow for a finer grind than an ordinary pump machine and almost eliminated channeling.
- The lever group head doesn't get dirty and back flushing is not needed as there is no exhaust solenoid - a simple wipe of the shower will keep it clean.
Q. What’s the difference between a Spring Lever Machine to machines we see in coffee shops?
Spring Lever Machines uses a group head spring to achieve the required pressure while modern machine uses pumps. There are no push buttons to make an espresso as there is no pump. When a barista pulls a shot, this literally means they pull down the lever(roughly approx 10kg of pressure) it loads a spring by elevating a piston into the cocking position. This allows water to enter the brew chamber to pre-infuse the ground at either boiler or line pressure. When the Barista releases the lever, the tensioned spring then pushes the piston down, forcing water through the coffee bed at high pressure which then decreases gradually to zero pressure.
Q. What is the taste difference between the lever and a commercial pump drive in the cup?
- When the Barista pulls down the lever -a pre-infusion occurs as water enters the brew chamber at a low pressure - determined by the Barista -This is different from most pump machines where pre-infusion can be electronically preset. This low-pressure preinfusion increases the surface area - so when the high 11 bar pressure exerted by the spring occurs a full extraction occurs - reducing channeling and increasing crema for a smoother fully bodied extraction.
- When the Barista releases the lever, the pressure can go as high as 12 bar or higher. This forces an even column of water through the coffee bed, whereas in a pump machine, water exit from a couple of small holes at the dispersion plate. This even water pressure enables you to have space above the coffee pluck without affecting extraction, which is something the pump machine cannot do.
- As the piston is pushing down, the pressure naturally goes to zero because of the spring. The barista can increase or reduce the pressure by manipulating the lever, which is exactly what some of the most advanced machines are trying to imitate electronically through the pump. These machines generally double the cost and one has to deal with electronic components, while most of the other pump machine has either line in preinfusion or full pressure to 9 bar only.
- The temperature of water in the group drops very slightly if not used right away - so a dry lever to flush out the colder water is recommended.
All these contribute to a fuller body more velvety mouth feel and an easier drinking cup with single-origin arabica or blends.
|
Galway, Ireland
