Pressure profiles, preinfusion and the forgiveness factor - Page 5

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Team HB

#41: Post by another_jim »

Jepy wrote: The pictured gauges are of similar pressure ranges, all marks should be roughly the same. What would you rather be reading from?
Think of it as 83 decibars rather than 8.3 bar, and then it's just as easy on the tongue -- the "point" bit is the annoyance; it doesn't scan well.

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HB (original poster)

#42: Post by HB (original poster) »

battlecry wrote:Would such a coil, or perhaps a water-hammer type damper, provide a steadier pressure rampup and brewing pressure profile?
That's one of the effects of the gicleur (shown in yellow surrounded by green) here (see E61 Group Espresso Machine: Detailed Interior Schematics for more).

The magnitude of the pulses are dramatically smaller post-gicleur, so much so that a snubber isn't necessary to get a steady reading at the grouphead -- even with an air gauge (I'm tempted to attribute some of this dampening effect to the OPV, but I've not isolated it). Chris argues that reducing "pressure flutter" is a necessary condition to produce The Elusive Clarity in the Cup; Andy also commented in the same thread:
AndyS wrote:Meanwhile, installing a water hammer arrestor to reduce "flutter" is dirt cheap. I've got one on my machine, but I haven't played with it in a while. Your comments have made me itching to compare results with and without it. I'm just not sure that the difference will be discernible amid the "noise" of my amateur dose/distribution techniques.
Honestly I don't have my head wrapped around the whole notion of "clarity" and I am thinking about how to reliably produce a side-by-side demonstration, e.g., taking a dampening agent on and offline as Andy suggests, or by switching between vibe and rotary pump on the fly.
Dan Kehn


#43: Post by battlecry »

Thanks. I'm going to do some more research on these issues. R.


#44: Post by HAL9000 »

Hi folks,

Sorry to resurrect this old thread, but the idea of what makes a particular machine "forgiving" (or "more easy to use") has been on my mind lately as I have been considering a single group machine to replace my three group Faema. I love the ease of use of the Faema, it is just too big for the kitchen, and now I have reason to want a machine in the kitchen.

Has anyone taken the idea of what makes a given machine more "forgiving" than another further in the last two years?

Also, if anyone knows, is the Astra Gourmet group design, which does not include a preinfusion chamber, considered "forgiving?"

Any thoughts appreciated.

Thank you,


#45: Post by CafSuperCharged »

Speaking about resurrecting an old thread...
Did any of the participants in this thread get any further?
Did you e.g. relate forgivingness and rotary pump without preinfusion to not tamping (more or less Italian style - less, finer coffee)?
It might be on the other end of the portafilter after all.



#46: Post by zin1953 »

A morning without coffee is sleep. -- Anon.