I PMd a knowledgeable user here on home-barista with a question, and he suggested I post it in the forums for discussion.
For the years before I had a decent semi-auto machine, I could swear that I noticed an immediate difference in shots pulled from a Synesso or GS/3, regardless of cafe/location, technique, quality, etc. (i.e., when I would visit various cafes). At first, I was not sure of what I was noticing. I would have described it as a purity or clarity to the shot, or water used for the shot. It was somehow clean. I realized I never noticed this phenomenon with other machines, even with professional water filtration systems. (And this is basically true to this day) And, this over the course of 7+ years, deliberately visiting 50+ cafes, etc.
As I accumulated knowledge on machines, I realized that the Synesso and GS/3 machine are distinct from most others in that they have stainless boilers (as many of you know). Owning both copper and stainless cookware, I was immediately reminded of the ease with which wet copper imparts odor to surfaces. My copper boiler machine (Alex Duetto II) imparts a similar copper flavor to the water (though mild, it is deep in flavor).
I had concluded that it must be in the extensive use of stainless in the Synesso and GS/3 that is largely responsible for the clarity in the cup, even with poorly pulled shots. But, I cannot seem to find explicit mention of this connection in blogs such as this one.
So, now I am a bit confused. I was hoping that people with experience on machines with copper and stainless boilers (especially GS/3 owners who previously owned copper boiler machines) might lead to some clarification on my question.
Thanks in advance for your thoughts!