[Homeroast] was Espresso advice *HiJacked* now presurized portafilters

raymanowen at gmail.com raymanowen at gmail.com
Mon Jan 11 03:35:15 CST 2010

When a liquid (Hot water) flows at a certain rate through a resistance,
(packed coffee puck) a back pressure is generated. (9 bar)
The 9 bar pressure exists only at the interface where the water enters the
puck, the pressure drops linearly as the water progresses through the
resistance puck.

At the bottom of the puck/ pf basket, the pressure of the espresso and crema
is zero. (Ø) It doesn't squirt out the bottom grid of the basket.

If the pressure is caused by a restriction after the flow through the puck,
the pressure in the puck, where the espresso extracts, will not have the
infinite pressure ratio of 9 bar/ 0 bar or 132 psi/ 0 psi. Any flow through
a resistance will still yield a pressure drop, (potential difference in
electronics) but the denominator is no longer zero so the ratio is no longer

Just like in grinders, you can't have perfection when every particle size is
different. Even David Kenmore offers no explanation of the physics of
espresso extraction. The facts are a little chilling to be wantonly ignored.

I have a new physiologic event- the Synaptic Dance when I try to brew
espresso. Variable pressure, temperature and particle size. Everybody does
it that way. It reminds me of The Infernal
<http://www.youtube.com/watch?v=XzDo-BX74uU&feature=related>movement of
Igor Stravinsky's Firebird. How in the world can all the variables make for
the Huge shots pulled by so many? Great when it all comes together.

Cheers, Mabuhay, Iechyd da -RayO, aka Opa!
Persist in old ways; expect different results - suborn Insanity...

note: this email sent on a teletype and wire photo transceiver via spark

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