Best flush routine for Bezzera Strega?

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sekihk

#1: Post by sekihk »

Did any of you seriously measure how the duration of cooling shot and the waiting time between the flushing and the actual brew had affected the brew temperature?

I had done nearly a hundred measurements by planting a looped thermocouple into stale coffee grounds (to resemble same flow rate similar to actual brewing - 30 seconds for about 30ml). I had saved some Artisan charts that recorded part of the tests. At original factory setting of pressure stat, brew temperature (no flushing shot and tested about two mins after last shot) was consistently starting off at 95'C and ending at 92-93'C. Then, the inconsistent part comes if you want to cool by flushing. If you flush, the duration of flush and the volume of water flushed out would affect brew temperature a lot (inconsistent results here: you may try using a stop watch to time the moment when water starts pumping out from the shower screen. It's very DIFFERENT every time). Especially if you pull the shot right after you finished flushing. In my trials, I could see brew temperature started at as low as 83'C (if you flush to the level when water is pumped out from shower screen and right after flushing you brew immediately). Other combinations of flushing time/wait time before brewing could give very inconsistent results (variation factors included whether the boiler and HX is running, whether fresh cold water had just been plumbed into the boiler, different volume of water that had flushed out even you had tried to flush for the same duration).

After so many tests, the only consistent temperature that I could get was by brewing a shot with no cooling flush, so that everytime I would get brew temperature ramped up to 95'C at about 10 seconds after water got into the coffee grounds (time was not counted after the pump started because it's no use to time the inconsistent pump). If you choose to flush, my observations was that no matter how you tried to time the duration of flush, and how long you waited before starting to brew after the flushing is done, you would still get inconsistent brew temperature every time.

I would appreciate if any of you can share your way to get consistent brew temperature. What I can figure out now is to lower the pstat so that when I do a non flushing brew, the temperature won't ramp up to 95'C.


...split from Owner experience with Bezzera Strega by moderator...

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sekihk (original poster)

#2: Post by sekihk (original poster) »

Here is an Artisan chart for no flushing brew temperature:


Here is another Artisan chart for brew temperature with different cooling flush setting, the last three in chart is brew without flushing (note the brew temperature can be fully recovered after 1.5 min of waiting time).


Given such inconsistent brew temperature if flushing had been conducted before brewing, no wonder why some of you would say the Strega might have cut off the extreme flavors in a blend.

EDIT: "inconsistent" - I refer to the different max brew temperature that you'd get if doing cooling flush before brewing. I'm not referring to the fact that the brew temperature profile was always a dropping profile.

wildbwilson

#3: Post by wildbwilson »

With these so called inconsistent brew temperatures - what does the coffee taste like?? I was just pulling some Intelly black cat this morning and my shots were glorious - dropping temp and all, with a VST 21 gram basket to boot. Dropping temp is what these things do!! If you are looking for absolutely stable temps why in the world are you using a lever machine? Levers never have and never will operate like a DB - ask Kees van der Westen about that one. If the coffee you're using does not give you the results you think you want, try a different coffee and another and another. If you can't live with out PID perceived wonder then gosh you're in for it. Drink more worry less.

sekihk (original poster)

#4: Post by sekihk (original poster) »

Don't get me wrong. I'm not saying I don't like the Strega or worried about "dropping temperature" during brewing. I never mentioned it's a problem with the "dropping temperature" if you've read my post (I guess you didn't). I was saying, if you do a cooling flush before brewing, you'd get different brew temperature no matter how consistent you had tried to perform your cooling flush. This time you'd start at 85'C, next time it might be 90'C and basically you don't know whether the change in taste was due to ground coarseness, dosing or just difference in brew temperature (starting temperature I mean).

espressotime

#5: Post by espressotime »

sekihk wrote:Did any of you seriously measure how the duration of cooling shot and the waiting time between the flushing and the actual brew had affected the brew temperature?

I had done nearly a hundred measurements by planting a looped thermocouple into stale coffee grounds (to resemble same flow rate similar to actual brewing - 30 seconds for about 30ml). I had saved some Artisan charts that recorded part of the tests. At original factory setting of pressure stat, brew temperature (no flushing shot and tested about two mins after last shot) was consistently starting off at 95'C and ending at 92-93'C. Then, the inconsistent part comes if you want to cool by flushing. If you flush, the duration of flush and the volume of water flushed out would affect brew temperature a lot (inconsistent results here: you may try using a stop watch to time the moment when water starts pumping out from the shower screen. It's very DIFFERENT every time). Especially if you pull the shot right after you finished flushing. In my trials, I could see brew temperature started at as low as 83'C (if you flush to the level when water is pumped out from shower screen and right after flushing you brew immediately). Other combinations of flushing time/wait time before brewing could give very inconsistent results (variation factors included whether the boiler and HX is running, whether fresh cold water had just been plumbed into the boiler, different volume of water that had flushed out even you had tried to flush for the same duration).

After so many tests, the only consistent temperature that I could get was by brewing a shot with no cooling flush, so that everytime I would get brew temperature ramped up to 95'C at about 10 seconds after water got into the coffee grounds (time was not counted after the pump started because it's no use to time the inconsistent pump). If you choose to flush, my observations was that no matter how you tried to time the duration of flush, and how long you waited before starting to brew after the flushing is done, you would still get inconsistent brew temperature every time.

I would appreciate if any of you can share your way to get consistent brew temperature. What I can figure out now is to lower the pstat so that when I do a non flushing brew, the temperature won't ramp up to 95'C.

To me it's about drinking coffee.It has to taste good.With the Strega I get the best coffee drinks I've ever experienced.Seldom do I get a shot that's bad.So to be honest I don't care about temperature curves and flush times.
Espresso isn't a science class to me.
Grind,rake ,tamp and enjoy a great espresso.( by F. G.)

sekihk (original poster)

#6: Post by sekihk (original poster) »

You may try no flushing with pstat tuned down. Should be able to get more consistent results due to more consistent temperature shot after shot.

Anvan

#7: Post by Anvan »

espressotime wrote:...So to be honest I don't care about temperatue curves and flush times.
Espresso isn't a science class to me.
I'm sure other readers feel the same way, but these science-y posts are often useful to the rest of us who enjoy that sort of thing.

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wildbwilson

#8: Post by wildbwilson »

I agree about the science class - I can appreciate that the tech guys love this type of info and I'm here as a Strega owner to chime in that if the shots taste great the machine is doing it's part. Most coffees though not all taste good at a variety of temps - with shifts to the grind, dose, time , water quality, etc. I even change from conical to flat burr on certain coffees. The Strega, as with most commercial style lever groups has/have declining temp profiles - this is inherently what makes them special.
If ones fav coffee doesn't taste great with the Strega or if one thinks they are being robbed of dynamic flavour components with the machine, maybe the Strega is not the right machine for that individual. I love levers, have been using them a long time and for my tastes, with my equipment the Strega delivers the goods.

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JohnB.
Supporter ♡

#9: Post by JohnB. »

sekihk wrote: At original factory setting of pressure stat, brew temperature (no flushing shot and tested about two mins after last shot) was consistently starting off at 95'C and ending at 92-93'C.
Since almost everyone who has posted here has a different "original factory setting" of the P'stat it would be useful if you mentioned yours. I've pulled shots with no flushing & it was too hot. As long as I keep the grind/dose in the same range as my Speedster I'm getting some excellent shots with none of the flavors "cut off". Grind too fine & the shots turn bland.
LMWDP 267

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another_jim
Team HB

#10: Post by another_jim »

My boiler set at 1.3 bar, and I run from 97C to 91C without a flush. A reasonable flush (2 to 4 seconds) doesn't seem to affect the final temperature much, but drops the initial temerpature to around 93 to 95. I really don;t worry much about it; but just do a short flush every time. I work the machine with dose, pressure and shot time, rather than temperature, and only change it for very acidic or flat coffees. I think this is a machine you start hot and finish cool for just about every shot.
Jim Schulman