Comment by eigenspace
8 hours ago
Well, I have good news and I have bad news for you, and they're the same thing:
An electric machine (other than the Decent) is not any more reproducible in terms of the outcome of the shot than a manual lever, and in many ways they're less reproducible. The reason is that the actual pressure the water is under is not the important thing, the important part of coffee extraction is how that water is flowing through the puck.
Due to just random happenstance configurations that the puck can settle into, applying the same pressure every time will not result in the same extraction every time. Someone skilled with a lever and who is used to knows what it feels like when a shot flows too fast or too slow can adjust the pressure on the fly to compensate, improving consistency.
The temperature drifting is by far the largest factor in reproducing the espresso shots not the water flow.
Not really a meaningful comparison because you haven't defined how much of a temperature difference versus how much of a water flow difference we're talking about here. But for most people, at least if they take the most basic level of care to not use water at like 85 degrees or 110 degrees, then no, that's just not really true.
There's a lot of folklore out there that's lingered from the early 2000s espresso community where it was widely believed that temperature was the holy grail control parameter, but now with modern instrumentation and temperature probes, it's been pretty much debunked. Temperature stability throughout a shot makes almost zero perceivable difference in taste.
It takes brew temperature differences swings of around 5 degrees Celsius before people can start to notice any difference better than random chance, and almost a 10 degree brew temperature difference before it gets to the territory of 'ruining a shot'.
Meanwhile, very small differences in puck preparation, including micron-differences in grind size, or sub-gram-level differences in coffee quantity have profound differences in flow rate, which has a very strong affect on coffee extraction levels, which has immediately recognizable differences in the produced flavours that a trained palette can reliably detect. This is before we even start talking about channeling which has an enormous affect on the coffee.
Manual control of the applied pressure can and does allow skilled people to compensate for those differences in flow rate, and combined with very basic attention to brew temperature, does help shot consistency.
So much bs that I don't even want to go further into discussion, sorry. I say this as someone who has made several thousands of espressos on E61 group machine. I'll let you have your own opinion but anyone who has made more than a few espressos will immediately understand if and when the temperature drifted away. Pressure? I've made espressos at 6 bars and 9 bars. Makes literally almost no impact or whatsoever. You're right though that 5 degrees Celsius is probably about the right minimum amount when the espresso starts to change in taste, and there's remarkably many machines which cannot sustain the temperature in shot after shot workloads.