The Relationship Between Water Temperature and Boiler Pressure on a Pre-Millenium La Pavoni - Page 2

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[creative nickname]

#11: Post by [creative nickname] »

There is no "ideal" manometer setting, if considered by itself. You have to consider the interaction between boiler pressure and the grouphead temperature. A hotter boiler can be counteracted by a cooler grouphead, and vice versa, to produce similar results in the cup. And if your shots are channeling to a significant extent, then you are going to have taste problems regardless of your water temperature.

So I'd say you should start by getting your basket prep routine dialed in so that you can get an even extraction, and then focus on getting a repeatable combination of boiler + grouphead temperature. Then adjust the temperature until the taste is where you want it to be.

And just as a rough guideline, I tend to pull shots with my boiler at around 0.7 bar, and with my grouphead starting at around 195F (but going cooler for some coffees and hotter for others, as necessary to balance flavors).
LMWDP #435

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drgary
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#12: Post by drgary »

Hi Charles:

If you read the threads on temperature control of a Pavoni or Cremina you'll see target pressures somewhere just below 1 bar. I tend to run 0.85 bar on my Millennium machine with a PSTAT, which is a similar concept. Pair that with measuring temperature at the group and you'll be good. Your La Pavoni is very capable when paired with a fine grinder. Here's a link to encourage you:

Breaking Through to Fine Espresso at Home

This may help too:

Tips for Controlling Brew Temperature on a Home Lever Espresso Machine
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

vze26m98 (original poster)

#13: Post by vze26m98 (original poster) »

[creative nickname] wrote:There is no "ideal" manometer setting, if considered by itself. You have to consider the interaction between boiler pressure and the grouphead temperature. A hotter boiler can be counteracted by a cooler grouphead, and vice versa, to produce similar results in the cup.
Thanks, this is very helpful because it suggests to me it's not necessary to bring the machine up to cruising temperature (for me, that's ~0.95bar) to pull a shot. Cruising would seem to eliminate a variable (boiler temp), but there's no reason why one can't juggle two at once (boiler and grouphead temp), which is what I've been doing.

Your example of pulling at 0.7bar is a confidence builder, as I had been getting excellent results pulling Hairbender at this pressure.

Thanks drgary for another link I'd forgotten about: "Tips for Controlling Brew Temperature on a Home Lever Espresso Machine." Many of these threads are worth reading multiple times.

I got the Pavoni because I thought I could make great coffee with it and my Pharos. And I've largely done that, with very few of my pulls in the undrinkable range. But I would like more consistency and control, so if I read that some new coffee is happiest pulled at 203F for example, I can get there with a minimum of error.

Thanks again, both of you! Charles

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homeburrero
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#14: Post by homeburrero »

vze26m98 wrote:Your example of pulling at 0.7bar is a confidence builder, as I had been getting excellent results pulling Hairbender at this pressure.
Brewing at 0.7 bar is not radically low. If you look at the La Pavoni site, you will see that the pStat settings for the new machines is 0.7 bar - 0.8 bar. And, according to Francesco Ceccherelli, there was a period around 1996 where service centers were setting the pStats down as low as 0.5 - 0.8 on the pre-Mil single-element models.

Since you have a manometer, you can switch it off and experiment with brewing way down in the 0.5 to 0.6 range. I do that a lot on my pre-Mil Pro, where I have my pStat set pretty high (I turn it on and let it come up to the 1 bar range when I do my steaming.)
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

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yakster
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#15: Post by yakster »

I believe that Doug from Orphan Espresso set my rebuilt Faemina to 0.3 bar on the low setting, but since I have a high / low switch instead of a pressurestat it's easy to flip up to high to increase the pressure for steaming milk.
-Chris

LMWDP # 272

vze26m98 (original poster)

#16: Post by vze26m98 (original poster) »

Two interesting comments yakster and homeburrero--

I had a very nice Hairbender for lunch today at 0.7bar. The Kimbo and Passalaqua seemed very chocolately last week at 0.5bar, but I doubt I would have considered 0.3bar.

I do intend to build a poor-man's Scace this week, to see if I can get a handle on how the actual water temps in the puck relate to these pressure readings.

Best, Charles

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homeburrero
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#17: Post by homeburrero »

vze26m98 wrote:I do intend to build a poor-man's Scace this week, to see if I can get a handle on how the actual water temps in the puck relate to these pressure readings.
Cool! The group temp is as important as the boiler, so you may want a thermometer on that as well - see Adding Thermometry to a La Pavoni Europiccola
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

vze26m98 (original poster)

#18: Post by vze26m98 (original poster) »

homeburrero wrote:Cool! The group temp is as important as the boiler, so you may want a thermometer on that as well
I have a cheapie K-type digital thermometer with 2 inputs, so one as a Scace-alike, and the other on the grouphead. And of course the manometer...

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hankbates

#19: Post by hankbates »

I have my pstat set at about 0.8 bar in my pre-m pro.
What seems to work best for me is to brew the first cup at the setting pressure, turn off the switch, steam down to under 0.5 bar with 1% milk and a cappuccinatore, turn the switch back on, and input hot water for successive cups when the gauge comes back up to 0.5 bar.
Since the group is continually being heated or cooled by many factors, the gauge pressure when inputting to the basket can be modified as needed to get optimum temperature when the hot water passes thru the puck. I find that pressures below 0.4 bar don't work too well to fill the group.
The cappuccinatore works for me adequately well over a wide range of pressure, and it only steams the milk which is added to the coffee. Not the best frothing tool, but most probably the easiest.
When driving a car, I also frequently use a cruise control....

vze26m98 (original poster)

#20: Post by vze26m98 (original poster) »

So I built my poorman's Scace:

The K thermocouple is inserted into an MCAL basket, about 10mm in, which by my calculations would put it about midway into the puck, assuming a 7mm grouphead lip.

I didn't realize that a friend had an Amprobe AMD-56, so I was able to record my first use of the sensor:

The red ET line is the external grouphead temperature, and the blue BT is the temperature inside the puck. This was my second pull, and I had let the Pavoni cool down for about 20 minutes before doing this.

My method is to do a short flush at 8.5psi (0.59bar), and then pull at 9.5psi (0.66bar). It's quite interesting that the temperature in the puck only hit about 182F, which seems a little low. (I'd expected the water temperature to be higher.)

Obviously, I'll do more extensive testing to correlate my manometer and grouphead temperature to water temperature during the pull.

Best, Charles