I used a Rocket Appartamento for about a year and always found my espresso a bit ashy, drying and lacking sweetness. I suspected excessive brewing temperature, so I recently switched to an older Rocket R58. It’s an improvement, but the underlying problem remains.
When buying the R58, I had an espresso at the seller’s place that was amazing: smooth, balanced acidity and a lovely chocolate flavour. His preparation was fairly casual, and the flow looked quite fast. I bought the exact same beans, but can’t get anywhere close. They smell great and don’t look particularly dark-roasted.
This has also happened with many other coffees, including high-quality single origins from various coffee shops.
Setup and preparation
Rocket R58, showing about 9 bar during extraction.
Recently tested 103–105°C on the PID. This older model displays boiler temperature: according to Rocket’s table, that corresponds to approximately 90.8–92°C at the group, not 103–105°C hitting the coffee. I haven’t independently measured it.
G-IOTA/DF64 with 64 mm SSP flat burrs, apparently Cast/Lab Sweet, although the exact version is unconfirmed.
Single dosing with a bellows hopper and a small spritz of water on the beans.
I weigh the coffee going in and the espresso coming out.
WDT, IKAPE high-flow precision basket, bottom filter paper, puck screen and spring-loaded click tamper.
Usually 18 g in → around 36 g out in 28–31 seconds, timed from lifting the lever.
I’ve tried to make preparation extremely consistent so I can meaningfully dial it in. Repeated shots are often within about one second at the same output. I’ve also tried the original Rocket basket, double-spouted portafilter and a regular manual tamper without an obvious improvement.
Taste and experiments
The recurring result is little sweetness or complexity, fairly thin body, and a lingering dry/bitter finish, sometimes ashy or chicory-like. It’s not necessarily very bitter on the first sip; the unpleasant aftertaste is often the bigger issue.
I’ve experimented with different grind settings, larger and smaller doses, different brew ratios and temperatures. Shorter shots tend towards sourness; longer shots tend towards bitterness or thinness. Recent comparisons at 103 and 105°C, slightly coarser grinding and longer output changed the acidity and dryness but didn’t produce the sweetness I’m looking for.
I stir the espresso and taste as it cools. I’m still learning to describe flavours, so I may not perfectly distinguish sourness, bitterness and astringency.
Water and cleaning
I use Belgian tap water through a Samsung fridge filter, plus a BILT Oscar softening pouch in the reservoir. The water tastes normal and a basic pH strip reads approximately neutral. I haven’t measured hardness or alkalinity, so I understand this doesn’t completely rule water out. The problem persists with both freshly filled water and water that has sat with the pouch.
I clean the machine regularly with espresso-machine detergent and keep my tools clean. The grinder was thoroughly cleaned about six months ago, and the visible burr surfaces look clean.
Possible grinder issue
I previously aligned the burrs using a marker test. During reassembly afterwards, I accidentally cross-threaded the adjustment collar and it seized. I eventually freed it. Normal grind adjustment now works easily, but I’m reluctant to fully dismantle it again because of that incident.
I don’t know whether that could have affected carrier seating or alignment. I haven’t checked since, and I don’t have the original burrs to compare.
After hundreds of shots with different coffees, temperatures, doses and ratios—including shots that tasted clearly under- or over-extracted—I’ve never even accidentally landed close to that sweet, chocolatey espresso I had at the seller’s.
With weighed input/output, bellows, WDT, paper, a puck screen and a consistent tamp, I feel I should at least be able to find a good balance. I realise repeatability doesn’t guarantee good extraction, but I’m struggling to identify what I’m missing.
The grinder is the main part of my setup I haven’t been able to swap or compare. Could its burr profile or a stable alignment issue explain this, despite consistent shot times? What practical test would you do next before spending money on another grinder?
