I've been playing with the volumetrics on my Aurelia — I never let the baristas use these for anything except flushing — in an effort to see whether overall shot consistency is helped, and also whether the use of volumetrics speeds dial-in (which is complicated by a timed-dose grinder).
Initially, my tests were going well: shot weights (yes, weighing the shots as they pull on a 0.1g scale) were consistent +/- 1-2g, and taste in the cup good, despite the shots "finishing" in a widely divergent range of times (anywhere from 26-31 seconds, based on what I was trying to get). Things looked promising, though the time differences nagged at me a bit.
But, a second set of tests was very concerning: If I placed an empty vessel beneath an empty (i.e. no coffee) PF and pushed the volumetric button, then weighed the result, I would get DRASTICALLY different amounts (weights) of water out from "shot" to "shot". Like up to 12 grams different.
So, my questions: Has anyone else done this little experiment on a volumetric machine? Did your results resemble mine? Does the absence of coffee, and thus the speed with which water flows out, have a negative effect on the volumetrics' accuracy?
And also, who out there has gone back to volumetrics as a method of more consistently tasty espresso, rather than simple efficiency?
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