Brew pressure gradient of espresso

#1: Post by **endlesscycles** » May 16th, 2011, 1:23 pm

cafeIKE wrote:Scrounge an old PF, remove the spout, buy a gauge from eBay, valve and fittings from local ironmonger and voila :
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All in, less than $20 and within a pound of the High Price Spread.
NOTE : Liquid filled is not required. Liquid filling damps vibration and lubricates the mechanism

That's nuts.
My thought on pressure is that the whole puck is NOT under the full 9 or whatever bar. Pressure affects the puck as a gradient. However, this is completely different. How are the fully pressurized shots?

...split from Effects of brew pressure on taste of espresso by moderator...

#2: Post by **cafeIKE** » May 16th, 2011, 1:33 pm

Nut's or not, a PF gauge will register the pressure on the TOP of the puck. The digital adapter, a Scace II and my parts bin gauge all register within 1# at the same flow. The parts bin gauge allows flow adjustment from zero to lungo to measure the effect of shot volume on pressure. Without flow, static pressure is measured and maybe somewhat higher than brew pressure

from Digital Pressure Adapter

May 16th, 2011, 5:02 pm

No, it's nuts if you are brewing with that PF, because it could allow the pressure from the top of the puck to equalize to the bottom which does not happen in normal brewing conditions.

#4: Post by **cafeIKE** » May 16th, 2011, 5:34 pm

That's funny. I mean hilarious. Do you also think we brews with a Scace?
The pressure at the bottom of a puck is almost zero. DOH !

May 17th, 2011, 10:28 am

cafeIKE wrote:

That's funny. I mean hilarious. Do you also think we brews with a Scace?
The pressure at the bottom of a puck is almost zero. DOH !

The pressure at the bottom of the puck IS zero under normal brewing. And that's what I'm saying. You have a portafilter that could be used to investigate the effect of pressure on brewing beyond just flow rate, as you can, as an exception to the norm, pressurize the entire puck from the top to the bottom.

I feel like I've expressed this idea a third time now, but you keep mocking it....I'm asking that you try it and report the results to the benefit of others.

#6: Post by HB » May 17th, 2011, 2:21 pm

endlesscycles wrote:I'm asking that you try it and report the results to the benefit of others.

Ah, I see. You propose that the flow of the espresso from the portafilter exit be restricted such that the entire puck is equally pressurized, not a gradient from top to bottom (?). Interesting.

Keep in mind that the upper lip of the basket makes a watertight seal against the grouphead because it's pressed tightly against its rubber gasket, but the underside of the basket lip does not make a watertight seal against the portafilter body. To do as you suggest, that interface would need to be watertight, e.g., by adding an O-ring under the basket lip. Otherwise the espresso would exit along the underside of the basket and cascade over the sides of the portafilter.

#7: Post by **shadowfax** » May 17th, 2011, 2:28 pm

What's being proposed (pressurizing after the puck/basket to normalize the pressure gradient, top to bottom, of the puck) has been done before. Pressurized portafilters anyone? Great other than the, er, reconstituted crema. No thanks; anyone who has a cheap $200-300 espresso machine can undertake that experiment.

May 17th, 2011, 4:30 pm

May 18th, 2011, 12:14 pm

So the closed minded snobbery and crema obsession of the 90's maintains a final outpost here while the rest of the coffee world finds cooperation and testing assumptions to the benefit of a better cup? Okay. Never mind, I'll find a more receptive audience elsewhere.

I just find it absolutely ridiculous to look at the title of this thread and consider the responses I've gotten.

#10: Post by **cannonfodder** » May 18th, 2011, 12:42 pm

Huh? Closed minded snobbery, not quite. As it was pointed out, what you are describing is a pressurized portafilter which most lower end machines use. By restricting the flow and forcing it out a small opening the coffee is artificially whipped into a crema like froth while doing little for the quality of the cup. It would be curious to see what effect it would have in a larger machine with fresh coffee. Pick up a needle valve and a couple fittings, get your portafilter pressure sealed and give it a try.

endlesscycles wrote: I'll find a more receptive audience elsewhere

Bye