The Ponte Vecchio Lusso was one of the models tested during the Lever Espresso Machine Smackdown and the only one with a themosyphon design. The others (Olympia Cremina, Elektra Microcasa a Leva, La Pavoni Europiccola) bolt the grouphead directly to the boiler. I've owned the Microcasa and Cremina for years and am well familiar with their thermodynamics. The Lusso's thermosyphon design is well known among E61s, but unique among small lever espresso machines. I was curious how well it worked with such a small machine and 1st-line agreed to source a custom 43mm thermofilter from Greg Scace so we could explore it more fully as part of the Buyer's Guide.
The thermofilter proved to be very helpful in refining the brew temperature protocol for the Lusso. In addition, I wanted to answer questions like:
- The Lusso idles cold. What's the optimal flush amount before brewing?
- After pulling a shot, how long before the brewhead cools enough to again act as a heatsink / thermal dampener?
- What techniques could be employed to reduce wait time between shots?
- Can flush amounts / delays be manipulated for more precise brew temperature?
- How capable is the Lusso of "on the fly" repeatable brew temperature manipulations?
As you see, the peak temperature is around 206 each time. Consistency is certainly good news; My other two levers would rise with each pull until the water flash boils immediately upon exit. But what about the water temperature rising so high above the desired brew temperature of ~201? Wouldn't that assure a bitter, burnt espresso?
Prior to the thermofilter's arrival, I had already gotten to know the Lusso quite well. It certainly didn't seem to run hot. When it took the road trip to Counter Culture one Friday morning for an informal side-by-side with their La Marzocco WBC three group, no one's comments even hinted at bitterness. Several attendees expressed surprise at how good the Lusso's espressos were (comments like tasty, smooth, good flavor, etc.).
I enjoy a good espresso imponderable. While it wasn't a mad obsession over the following months, I wanted to better understand why a small, unassuming working-class lever espresso machine avoided the brew temperature machinations of its far flashier cousins. Over the next two weeks, I'll share my thoughts and welcome your explanations of this espresso imponderable.
For the benefit of those new to the group designs of these lever espresso machine designs, here's a brief recap:
For all of these espresso machines discussed in this post, the boiler is under steam pressure of approximately 1.0 bar, thus the water boils around 250 degrees Fahrenheit instead of the usual 212 at sea level. Subsequently the water must be cooled to brew temperature by the grouphead acting as a heat sink. But even if not brewing an espresso, the Cremina/Microcasa/Europiccola espresso machines will overheat when idle, simply by the conduction of heat from the boiler to grouphead. There are various tricks one can employ like wrapping a cool towel around the grouphead or locking in a cold portafilter to reduce the grouphead temperature. A thermosyphon design separates the grouphead and boiler; two thin pipes run from the boiler to grouphead and the difference in temperature of the water in the upper (hotter) and lower (cooler) leg of the loop creates a siphoning effect, drawing the water from the boiler to the grouphead and back. Because no thermosyphon is 100% efficient and because the grouphead radiates heat itself, the effective grouphead temperature is approximately the desired brew temperature. The length and diameter of the upper/lower legs of the thermosyphon loop can be changed to increase or slow the speed of the water circulation, which increases or decreases the effective grouphead temperature. While not directly applicable to the Lusso, the discussion of the thermosyphon of E51 espresso machines is presented in How I Stopped Worrying and Learned to Love HXs.