Comparing my coffee review to others, it seems that my Conti Prestina extracted more sweet fruit flavor than was done on other gear, specifically a distinctive raspberry note. This made me wonder whether the declining pressure and temperature
profile of my Conti lever extracted more pleasant flavors from this relatively dark roasted blend. Dave's review shows more fruit flavors emerging at the lower range of the roaster's recommended profile. So that's a vote for lower temperature revealing more of that flavor.
My results are very preliminary, but this morning they were supported by pulling this coffee on my Lady Duchessa spring lever and my Olympia Express Cremina manual lever. The raspberry flavor note that consistently revealed itself with my Prestina pulls showed up again on the Lady Duchessa. More fruit flavors appeared on my Cremina when I pulled a cooler shot and emulated the declining pressure profile of the spring lever. But that fruit flavor was stronger with the Duchessa and strongest with the Prestina. Why?
The Conti Prestina has a group with a dipper tube. The group is attached to the boiler with four bolts and is not actively heated between shots except through heat transfer where it is bolted on. The group weighs 18 lbs, so it's a massive heat sink. Long ago I inserted a thermometer in the basket and found that the Prestina has a significant temperature decline during the shot
My rare, vintage Lady Duchessa home spring lever
has a very similar design to early commercial lever machines. The group is separated from the boiler. It isn't actively heated and is bolted on. Water enters from a dipper tube. With its spring and cam mechanism, the group is more massive than that on the Cremina, so it is likely to lose more heat during the pull versus the mostly rising shot temperature profile typically seen with manual home levers. This graph
shows Gabor's excellent temperature study comparing an Olympia Cremina with a Club. Contrast the rising shot temperature of the Cremina and the declining one in the Club.
I will note that my Lady Duchessa has an added booster spring
as a reversible mod, and its shot style is similar to the Elektra Microcasa a Leva. (The old spring may have optimized traditional dark-roasted coffees but would barely produce crema.) As I got closer to dialing in this blend I found the raspberry note emerging more strongly than with the Cremina. I haven't put a temperature probe into the Lady Duchessa and am not about to drill a hole in its vintage basket to do temperature measurement. But the result is suggestive that declining pressure and temperature bring out the best in this coffee, revealing more varied flavor layering and reducing the dominance of other flavor notes.
Few people have a Lady Duchessa for such experimentation. I found myself appreciating the effort put into its design, including a manometer placed behind the group but easily visible from above. This gives a good sense of water temperature in the boiler.
There is a temperature stat underneath that controls the shutoff point of heating. The machine doesn't have a sightglass but is unlikely to burn out the element because heating is initiated by pressing the telegraph key power switch on the lower right which turns it on for one cycle.
I haven't recently tested the accuracy of the vintage manometer but can say that shots were more fruity when pulled when it indicated 1.0 bar than 1.5 bar, with the machine fully warmed up. I will continue to dial in Espresso Lusso's Gran Miscela Carmo (frozen at Day 6 post-roast) on the Lady Duchessa, tightening the grind to emphasize the declining temperature profile with a longer pull. Currently the longest I achieved was 22 seconds. (Added 7/16: By tightening the grind I was able to extract some raspberry flavor with the Lady D this morning and one very nice pull where I held back the lever a bit. It tasted like sweet pipe tobacco with a hint of raspberry. When I pulled a shot at too low starting temperature the raspberry wasn't evident.) The best pulls with the most distinctive raspberry note were on the Prestina with unfrozen coffee, a 30 second preinfusion and about a 33 second pull following that. (Added: Using coffee frozen at Day 6, I was able to pull a Prestina shot with 18 gm in, 35 gm out, 40 second pull, where the raspberry was again evident, though softer, accompanied by a smooth almond bitterness. The raspberry wasn't overpowering but is a blend component adding complexity.)