Uploaded November 2025 | Updated September 2026, 1 week ago
Time for a partial disassembly, aggressive cleaning, and thorough lubrication of my E61 espresso machine. I've detected a stale, metallic flavor in the water passing through the E-61 group. Has this ever happened to you? Water from the service boiler tastes fine, even after sitting in the machine for days. But when I taste it alongside the brewing water, sometimes there's a striking difference. And not in a good way.
(BTW, that 'music' you hear is me trying to recall Dave Van Ronk's "Green Rocky Road;" just noodling up some corny blues in G; and trying to remember "Hesitation Blues" on my beautiful Larrivee OM-9, which I modded and documented here: youtube.com/watch?v=tby_vX9RV9c )
The Backstory: I'm confident in my water quality; the source is very clean, far from industry or agriculture, and I use an activated carbon / ion exchange filtration system I've trusted for over two decades.
To find the source of that flavor, I drew samples of water from the group, and from the steam boiler; next, I drained the brew boiler directly to fetch a sample of that. All of the water samples from the machine had boiled. So for a control sample, I drew some filtered tap water--exactly what I use in the machine--and boiled it in a stainless kettle. That's important since dissolved O2 can affect your flavor perception and even the formation of flavor compounds.
Once the four samples cooled, I tasted all of them blind and had my wife mix them up and I tasted again. Then she tasted them. We repeated that four times, and each time we picked the sample that had passed through the group. It tasted stale, oxidized, almost rancid but not exactly, and had a sharp, metallic aftertaste. It also had a stale smell. I suspected something to do with oxide formation in the group, and something to do with friction.
It can't be related to the internal reservoir or the pump, because that would have turned up in the samples that I drew directly from the brew boiler and from the service boiler. It can't be related to the upper chamber with the mushroom valve and the copper tubing for the thermosyphon because water circulates constantly through there and back into the brew boiler, so any off flavors originating in that area would have been present in the sample that I drew directly from the brew boiler. So we can rule out the reservoir, the pump, the brew boiler, the copper tubing, and the upper chamber of the group.
But somewhere in the group something definitely was happening, and the likely suspect was the chamber with the cam and the cam axle. That's where water would be exposed to oxide particles caused by metal on metal friction. And the water in that chamber, of course, goes into your coffee. So my focus here is cleaning effectively and preventing friction with proper lubrication.
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Donate to the UNICEF Palestine Emergency Appeal: unicef.org/appeals/state-of-palestine
#espresso #coffee #e61
Audio capture: Zoom H-5
Audio edited with WaveLab Elements 10.0.70
Video Capture: Panasonic HC-X920
Video edited with DaVinci Resolve 18.0.3
Still images edited with Gimp 2.10.240
Production Assistant: Leo Greene
Music:
Kalimba Relaxation Music by Kevin MacLeod
License: filmmusic.io/standard-license
Time for a partial disassembly, aggressive cleaning, and thorough lubrication of my E61 espresso machine. I've detected a stale, metallic flavor in the water passing through the E-61 group. Has this ever happened to you? Water from the service boiler tastes fine, even after sitting in the machine for days. But when I taste it alongside the brewing water, sometimes there's a striking difference. And not in a good way.
(BTW, that 'music' you hear is me trying to recall Dave Van Ronk's "Green Rocky Road;" just noodling up some corny blues in G; and trying to remember "Hesitation Blues" on my beautiful Larrivee OM-9, which I modded and documented here: youtube.com/watch?v=tby_vX9RV9c )
The Backstory: I'm confident in my water quality; the source is very clean, far from industry or agriculture, and I use an activated carbon / ion exchange filtration system I've trusted for over two decades.
To find the source of that flavor, I drew samples of water from the group, and from the steam boiler; next, I drained the brew boiler directly to fetch a sample of that. All of the water samples from the machine had boiled. So for a control sample, I drew some filtered tap water--exactly what I use in the machine--and boiled it in a stainless kettle. That's important since dissolved O2 can affect your flavor perception and even the formation of flavor compounds.
Once the four samples cooled, I tasted all of them blind and had my wife mix them up and I tasted again. Then she tasted them. We repeated that four times, and each time we picked the sample that had passed through the group. It tasted stale, oxidized, almost rancid but not exactly, and had a sharp, metallic aftertaste. It also had a stale smell. I suspected something to do with oxide formation in the group, and something to do with friction.
It can't be related to the internal reservoir or the pump, because that would have turned up in the samples that I drew directly from the brew boiler and from the service boiler. It can't be related to the upper chamber with the mushroom valve and the copper tubing for the thermosyphon because water circulates constantly through there and back into the brew boiler, so any off flavors originating in that area would have been present in the sample that I drew directly from the brew boiler. So we can rule out the reservoir, the pump, the brew boiler, the copper tubing, and the upper chamber of the group.
But somewhere in the group something definitely was happening, and the likely suspect was the chamber with the cam and the cam axle. That's where water would be exposed to oxide particles caused by metal on metal friction. And the water in that chamber, of course, goes into your coffee. So my focus here is cleaning effectively and preventing friction with proper lubrication.
========
Donate to the UNICEF Palestine Emergency Appeal: unicef.org/appeals/state-of-palestine
#espresso #coffee #e61
Audio capture: Zoom H-5
Audio edited with WaveLab Elements 10.0.70
Video Capture: Panasonic HC-X920
Video edited with DaVinci Resolve 18.0.3
Still images edited with Gimp 2.10.240
Production Assistant: Leo Greene
Music:
Kalimba Relaxation Music by Kevin MacLeod
License: filmmusic.io/standard-license
