Olympia Cremina Temperature Study, Part 2 - Page 2

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tekomino (original poster)

#11: Post by tekomino (original poster) »

bostonbuzz wrote:I only had enough beans for one shot today, but it tasted a bit sour. My machine jumped up to 176 by the time I could pull, and the shot tasted sour. I also checked my pressure, and it's .75-.9 now. The shot tasted sour, but it probably should have been burnt. Perhaps our machines are different?
Regarding group-head to shot-temp relation our machines should be very close. I will go opposite to what some claim, but shot sourness in my opinion is caused first and foremost by coffee you use, then by how fine you grind and at the end and by very small amount, by temperature. Temperature in my experience brings flavors forward, makes them clearer but it does not make shots go sour. I am talking about temperature ranges from say 190°F-210°F.

So low temperature will make shots taste bland and flavors muted. High temperature will amplify all flavors including any sour notes.

So if your group-head was at 176 and boiler pressure even at .9 bars you should have about hot temperature shot but not burned. If anything higher temperature shots will amplify the sour flavors in coffee...
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bostonbuzz

#12: Post by bostonbuzz »

Hmm, very interesting. I have to say the cold=sour thing has been throwing me off ever since I started.
As to our machines having similar temperatures, what is your grouphead temperature mid shot and at the end? Mine is between 180-192 I believe, but I'll have to check again. I thought that this might be closer to 200F, but it settles lower. Do you think there is a direct relation to the settled mid-shot group temp. and the brew temp?
This is just curiosity, since at this point I should probably get away from the numbers and adjust by taste.
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bostonbuzz

#13: Post by bostonbuzz »

A useful chart for Cremina users with thermometers attached to their groupheads. Assuming that your pstat goes between .7 and .9.

First, my data from the above charts:
Grouphead change: +/- 2.5F = +/- 1F brew
Boiler: Top (.9)= +2F Brew Bottom (.7)= -2F Brew [4 degree difference]
(Even though the water temp is 8 degrees different)


You can brew either at the top of the cycle (release some steam to start the boiler), or at the bottom.
When going with the bottom (.7bar) I like to release steam to start the boiler while I grind, and usually when I'm ready to pull the boiler is about to turn on again. Right when the light goes on, you turn off the machine.

.9 = not possible COLD
.9 @ 165= 200F MED
.9 @ 170= 202 HOTTER

.7 @ 165= 196F COLD
.7 @ 170= 198F COLDER
.7 @ 175= 200F MED
.7 @ 180= 202F HOT

I hope this is useful to some people. From the shots I've pulled this week, this seems to be quite accurate.
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dergitarrist

#14: Post by dergitarrist »

At the risk of overcomplicating this... have you tried what effect the water level in the boiler has? I can't shake the feeling that, temperature-wise, I get the most consistent shots at around two thirds, three quarters full.

Sorry for bugging you with requests like these but you have quite a nice testing setup there. I'd love to play around with that for a few days. ;)
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tekomino (original poster)

#15: Post by tekomino (original poster) »

dergitarrist wrote:At the risk of overcomplicating this... have you tried what effect the water level in the boiler has?
I did not explore that honestly. You would not believe how much time and energy it takes to do things like that so I try to limit what I look at :D
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dergitarrist

#16: Post by dergitarrist »

I understand completely. ;)
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orphanespresso

#17: Post by orphanespresso »

I have been watching The Tekomino sessions with great interest and hoping for more of his mega temp studies using his probe/basket as this setup seems to be presenting a better picture of shot temp vs simple exterior skin group temp. His last study of the Goldilocks paradigm (cold medium and hot) groups and shots seems to make a lot of sense...but with different beans requiring different temps it may not be that Goldilocks is the best term as there may not be a "just right". So I have been working on the idea of a thermal break setup for the model 67s.
Before jumping on the thermal break bandwagon we are doing some long run time experiments on model 67 to see just the effect of a full face insulating gasket at the group to boiler position. There is no evidence that 1/8" teflon is going to be ideal here and it is hard to translate a commercial group to the much less massive 49mm Cremina (or Pavoni) group as far as thermal behaviour. I have been using high temp silicone as a start since it is easier to cut and 1/8" keeps the group idling in the low 170F range from one day's trial run. 1/16" has about the same effect on a short follow up test. Tuning this gasket to run at 175 might be ideal but it will take some time and lots of temp readings to create a gasket to give a constant or in the ballpark temp on all of the model 67s. One thing so far is that it takes a LOOONG time for the group to warm up to temp with a thermal break without flushing, which of course depletes the water in the boiler, so some balance needs to be achieved. Even a short flush can spike the group temp readings, generally about 20F on a short flush and then a slow coast back down but this may give even more erratic temperature at point of pull, unless you have the thermocouple on the group, which is not the goal here, at least IMO, since too many inputs and wires on a Cremina tend to defeat the beauty of the machine.
Also, we have a 2011 machine and will take off the group and see just what is in there....we may be all making assumptions here from the 2002 machine that had a lot of quirks as far as heat breaks and teflon seals and the works...the group to boiler seal on that one was 1/8" goretex and Olympia really backtracked after the 2002 model to a more standard 'tried and true' format for the machine so we there may be a lot of assumptions out there in this issue right now...the thermal break gasket may just be snake oil in a sense but if it is not then some numbers will help prove it out.
There is always the question, if this is such a central issue, why didn't Olympia bring in a heat break gasket...it's not like they are espresso machine dummies. They went way overboard on the 2002 model with new this and that and by and large pulled back on most of the changes...was this a case of some new engineers running amok with a proven format only to have cooler heads prevail in the long run?

By the way, from a week of running a model 67 with a k thermocouple on the group exterior, runs at an average 193-195F depending on the ambient temperature....8 hour runs, no flush, readings taken every 15 minutes, pstat set a 1 bar max.

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bostonbuzz

#18: Post by bostonbuzz »

It's good to see that orphan is working on this. I'm sure you saw my thread with the 1/8" teflon. It idles at 170. One thing to keep in mind is that there is no need to flush any water at all to raise the group temp. One pump to circulate the water in the grouphead gets the group jumping up one degree per second. It does take a few pumps (3 at 1 min intervals) to get up to brew temp, however.
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tekomino (original poster)

#19: Post by tekomino (original poster) »

Doug, its great you are looking into this.
orphanespresso wrote:One thing so far is that it takes a LOOONG time for the group to warm up to temp with a thermal break without flushing, which of course depletes the water in the boiler, so some balance needs to be achieved.
I would not worry about this since it is easy to warm up group with half pumps and by letting just little water out for lubrication. Biggest problem with Cremina that I see is that you are good for at most 3 shots before you actively need to cool down group head. Now, if you only make 2-3 shots anyway you are good to go regardless. I suspect that most of Creminas are used that way thus Olympia did not do anything about thermal break.

And since machine comes up to temperature very quickly I think they assumed you simply turn it off when not using it so there was no reason to make it idle cold...
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peacecup

#20: Post by peacecup »

Biggest problem with Cremina that I see is that you are good for at most 3 shots before you actively need to cool down group head. Now, if you only make 2-3 shots anyway you are good to go regardless. I suspect that most of Creminas are used that way thus Olympia did not do anything about thermal break.
Isn't this the problem with all pressurized home levers? At least that's always been my understanding. As long as one only wants to make 2-3 shots at a time, no problem.

The big question is why didn't Olympia make the new Cremina open boiler with a designated steam boiler. That's what the home lever world is waiting for. Meanwhile all the Caravels still sitting around Italian attics find their way to ebay sellers who forward them to home lever enthusiasts worldwide who want accurate and precise temperature control.

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