I have attached a picture of the BOSCO espresso machine now in place at the Caffe Vita in Fremont.
This machine is a classic lever machine. The use of a spring instead of a pump to provide brew pressure is the main difference between lever machines and conventional, traditional-style espresso machines. The BOSCO lever has no pump and motor–so brewing is quiet.
But first some background on lever machines. . . To make coffee on a BOSCO or virtually any other lever machine, you pull down a handle which compresses a large spring located inside that tall cylindrical area above the group. This action allows water to fill a chamber. (With lever machines the volume of water for brewing is fixed, predetermined by the size and volume of this chamber.) As the spring returns to static position, moving against the resistance of the tamped coffee in the portafilter, it gradually forces water through the coffee. The quality of extraction with a lever is different from a conventional espresso machine, because of the way springs relieve the force applied to them. This is a physical property of springs, and graphs in the case of espresso machine applications as a straight line of pressure reduction over spring length.
Many people who have used lever machines describe a “softness” to the extraction, compared to pump powered brewing. In my experience, espresso brewed this way is usually favored by coffee aficionados who are familiar with espresso brewed from conventional, traditional-styled machines–preferred when they can get it right, that is.
The Downside of Lever Machines . . .
“Getting it right” is an an iffy proposition with a lever machine. The giant five-group leviathan from BOSCO, has some design characteristics that take steps backwards in terms of brew quality. Most notably, brew temperature control is sacrificed, as this is a heat exchange system, often referred to as a single boiler system, where steam and brew water are linked like Siamese twins to one large tank that serves two purposes Erratic brew temperature usually results from systems like this as the need for higher temperature steam (212 degrees F) battles with the countervailing requirement for much lower temperature brew water (196-203.5 degrees F). Scorched coffee is often the bad outcome from this struggle, as steam is a glutton for more heat and simply won’t happen at less than boiling.
Lever machines do best when espresso extraction is continuous. That is, when drinks are made one after another, without big delays between drinks or huge requirements for steamed milk. A store that serves large numbers of 20 oz Breve Lattes would probably do well to steer clear of a lever machine like this, as would any store that must steam milk continuously for more modest sized beverages, with the exception of classic macchiatos.
Learning the Ropes at Caffe Vita
To this point, our first espresso pulled from the BOSCO was bitter and uncharacteristic of the usual quality of Vita coffee, while our second, third, fourth, and fifth beverages, including a macchiato were much, much better. After that we were so caffeinated that we could barely sit down, and our espresso sampling was OVER.
All these pros and cons noted, I love seeing a lever machine in a Seattle cafe, especially one as prominent as Vita. A lever machine is finicky, high-strung and greyhound-like. Lever machines are the most theatrical of all espresso machine types, and the quality of the performance is easily tasted in the cup. Lever machines require a level of barista skill and judgement that most other machines do not. But levers also empower the user to make espresso brewing more than rote action.
Experienced lever-machine- operating baristas will pull the handle down and not release it immediately, delaying extraction to allow pre-infusion before they engage full-on spring-powered pressure. By feel alone a good barista knows what temperature their machine is at and how it will effect the coffee. For me, anytime you can combine human skill and judgement in producing that ultimate God-shot, it’s a good thing. It is unfortunate that the BOSCA machine is decked out the way it is, because with its garish gold & silver design treatment it is likely to be dismissed as a mere novelty item, instead of the radical departure from convention that it truly is. Still, that is simply personal taste and I recognize that others may actually love the look–like Tony Soprano, for example. Anyway, hats off to Caffe Vita for giving us a chance to experience this espresso brewing tradition, first-hand.