vit wrote:It would be interesting to know what is approximate temperature drop of the water inside brewing chamber during extraction.
Is someone willing to try measuring it somehow ?

Interesting but largely meaningless. Since this is a non-pressurized passive (not open-boiler) pour-over espresso machine, the reality simply is that you can only control (and reasonably measure) the inputs. The great thing about it though is that the temperature drop - whatever it is - with a consistent workflow will be consistent. I have personally had no issues (~sea level) getting a 96c start temp (that being a reading on a thermopen at or above 96c for a couple seconds after filling). After this point, measurement in the open cylinder is pointless as the main cause of heat loss is the open top. Insertion of the piston will slow that loss, and waiting is not advised.

I suppose, only possible procedure would be this: make a coffee as usual with preheating and known starting water temperature. After making espresso, removing brew chamber together with piston, PF and basket, turning it upside down, removing PF and basket from the chamber and checking remaining water temperature with thermometer?

I think measuring the output is probably easier in terms of answering the question "is there a noticable loss of heat DURING extraction". Obviously, as we all know, the coffee bed and portafilter/basket will absorb some heat, and espresso is generally no where near the start temp of the input water. But if you measure emerging espresso for the duration of extraction, you can probably get a good idea whether or not heat is being lost outside of the system (I've never done this, but I'd guess that temperature should rise slightly over the duration. If it's dropping as the shot progresses, then you could assume that it's loss to the surrounding environment.

To add to that, it would probably be the case for ALL levers that there's a temperature decline of the water in the grouphead, since they sort of all work on the same principle.

For example, my LPE fills the group at lever-up, so once the water and grouphead roughly equalize in temperature, the only direction for that temperature to go during the shot is down (though it may be only slight). I'm not a physics major, so I don't know what the increase of pressure does (that's technically an input of energy so wouldn't that raise temp slightly)? Either way, as I mentioned, this is intermediate data and something we have no control over anyway, so with my light roasts I aim for "consistently as hot as possible", and haven't had a problem with the output.

For what it's worth, I did try actively heating the cylinder beyond 100c on my stove top. I wasn't really paying attention though and took it a bit too far.

When I popped it on the pf, the pf melted a tiny bit, and introduction of water to the cylinder was ... exciting.

instantkamera wrote: I think measuring the output is probably easier in terms of answering the question "is there a noticable loss of heat DURING extraction". Obviously, as we all know, the coffee bed and portafilter/basket will absorb some heat, and espresso is generally no where near the start temp of the input water. But if you measure emerging espresso for the duration of extraction, you can probably get a good idea whether or not heat is being lost outside of the system (I've never done this, but I'd guess that temperature should rise slightly over the duration. If it's dropping as the shot progresses, then you could assume that it's loss to the surrounding environment.

I asked that because I have a home made espresso device, assembled out of 1 cup moka pot, equipped with tyre valve and I use a bike strut pump to achieve the needed pressure (9 bar or even above is not a problem) - I posted the picture in the post in the brewing section while we were discussing moka pots. It has similar size like cylinder of Flair and holds about 75 ml of water. Out of it, about 25-35 ml remains after extraction. I usually start the extraction at 92-94°C (temperature surfing is very easy, consisting of boiling the water in the pot itself, waiting predefined time in range 20-60 sec, mounting the basket and extracting the espresso). However, a few weeks ago, I measured the temperature of remaining water in the pot (by inserting the thermometer through the valve, say 15 sec after I finished the extraction) and it was lower than I expected, only about 84°C. I did that after making some coffees with SO from local roaster and the coffee, although quite similar like on his espresso machine (set to 93.5°C), was somewhat lacking chocolate tones. Of course, I'm well aware that a simple device that costed me 20 EUR + pump can't achieve the same result like 5k+ machine and Feldgrind also isn't the same quality like his grinder, but I did that measure afterwards trying to determine the cause. So I was just interested is Flair better in this regard, because I made this device just as experiment for possible travel kit before the Flair existed, and will eventually replace it with something more convenient, but it turned out that coffee is considerably better than expected so it remained in use considerably longer than initially expected, replacing my DeLonghi EC 150

Lever machines are slightly different anyway, brew chamber is indirectly connected with the heat source and whole brew head has higher thermal mass, so I expect this temperature drop to be smaller, but in case of Flair, it looks similar to my device in terms of thermal capacity.

vit wrote: Out of it, about 25-35 ml remains after extraction.

with the flair, generally speaking no water remains outside of that absorbed by the puck, which isn't very soupy.

I usually start the extraction at 92-94°C (temperature surfing is very easy, consisting of boiling the water in the pot itself, waiting predefined time in range 20-60 sec, mounting the basket and extracting the espresso).

temp *consistency* is similarly easy with the Flair, preheat cylinder and boiling water in will always give the same start temp.

However, a few weeks ago, I measured the temperature of remaining water in the pot (by inserting the thermometer through the valve, say 15 sec after I finished the extraction) and it was lower than I expected, only about 84°C.

I'm trying to visualize this, but I genuinely think this measurement is meaningless. For one, 15s is half the time of a full extraction (give or take), and about 1/3 of the total time since you would have started the pull. So at least 1/3 of that temperature drop doesn't even apply to the pull "window" - but probably less because the decreased mass of water is likely to give up it's heat faster too.

So I was just interested is Flair better in this regard, because I made this device just as experiment for possible travel kit before the Flair existed, and will eventually replace it with something more convenient, but it turned out that coffee is considerably better than expected so it remained in use considerably longer than initially expected, replacing my DeLonghi EC 150

Not having *any* experience with your home-made deal, I would say that perhaps the one difference is the mass and material of the brewhead. Is yours the thinner and lighter Aluminum I'm picturing a Moka pot to generally be made of? If so, it likely doesn't match the thermal capacity of the Flair's SS cylinder, which is nearly 1/4 of a kg and covered on the outside with silicone to reduce heat loss (and to make it easier to handle).

That said, you still have a fixed temperature to start with, and no way of re-introducing heat to the water during the pull.

I don't see this as an issue though, and I'd argue that "lacking chocolate tones" is far too vague an subjective a criteria. This machine can easily over extract medium to dark roasted coffees, and the variables of temp/time/grind/dose are all capable of bringing most coffees into the zone, in my experience.

Lever machines are slightly different anyway, brew chamber is indirectly connected with the heat source and whole brew head has higher thermal mass, so I expect this temperature drop to be smaller, but in case of Flair, it looks similar to my device in terms of thermal capacity.

See above.

Thanks for the info. I just try to estimate what to expect from Flair in case of buying it, when/if retailers here in Europe start selling it

Yes, moka pot is made of aluminum. Mass of the pot is about 110g, basket fits inside it, while upper part is about 50 g. However, specific heat capacity per kg of aluminum is almost twice of the steel, so heat capacity of if seems to be similar to Flair if it is around 250g

I'm aware that measured water temperature was probably about 2°C lower than the temperature at the end of the "pull", but decrease from say 93 to say 86-87 within 25-30s still sounds like a lot. However, with somewhat darker roasted italian blends with some robusta I'm usually using, I really enjoy the result. Maybe this measurement isn't really accurate due to small amount of remaining water etc ...

How much water actually fits into Flair cylinder before extraction and how much espresso you usually get out of it?

If you want the SS piston, I just saw that it is now for sale and it's $10 off the $30 price for the first 50 sold.
http://www.flairespresso.com/product-pa ... eel-piston
I have No affiliation.

vit wrote: Yes, moka pot is made of aluminum. Mass of the pot is about 110g, basket fits inside it, while upper part is about 50 g. However, specific heat capacity per kg of aluminum is almost twice of the steel, so heat capacity of if seems to be similar to Flair if it is around 250g

Ill come back to this, as I'm actually not sure this is accurate/what really matters...

I'm aware that measured water temperature was probably about 2°C lower than the temperature at the end of the "pull"

Why only 2°C? If your pull was 30s, and you waited 15s, that's a total of 45s(of which your "delay" before reading is 1/3rd) and a drop of 10°C. At the very least, that equals ~3.xx°C *if* you assume that something else didn't rob a lot of heat after extraction was complete (I'm not convinced that is the case).

Maybe this measurement isn't really accurate due to small amount of remaining water etc ...

I think there is too little data, and too many variables to trust that. I trust my palate...

How much water actually fits into Flair cylinder before extraction and how much espresso you usually get out of it?

I think input is ~65ml. With the avg dose of about 16g (I often go higher though), you can pretty reliably get 36g+ out. This better than my Pavoni on a good day, and closer to what 3rd wave folks are doing in my area these days (if a little short still).

instantkamera wrote:Why only 2°C? If your pull was 30s, and you waited 15s, that's a total of 45s(of which your "delay" before reading is 1/3rd) and a drop of 10°C. At the very least, that equals ~3.xx°C *if* you assume that something else didn't rob a lot of heat after extraction was complete (I'm not convinced that is the case).

I presume that presence of the wet puck being in the same chamber as the water remaining after extraction (both Flair and my device), without extra hot water flowing in like in boiler machines, is causing measurement being lower than expected. Of course, it's questionable how much of importance it actually is

Actually a while ago I measured water temperature drop in the pot alone (without basket and upper part) and it was much slower - at 1 min after boil temperature was 93.5°C, at 2min it was 89°C and at 3 min it was 85°C, that's why I was surprised with this

Another thing that is different with my device is relatively steep pressure curve - with this small pump, I need 6-7 s to achieve 9 bar, while in lever machines including Flair it's considerably faster. However, there were various discussions about influence of it on this forum and elsewhere, but without some definitive answers how this affects the taste ...

vit wrote: Yes, moka pot is made of aluminum. Mass of the pot is about 110g, basket fits inside it, while upper part is about 50 g. However, specific heat capacity per kg of aluminum is almost twice of the steel, so heat capacity of if seems to be similar to Flair if it is around 250g

So I did some thinking about this and conferred with others. I misspoke when I mentioned "thermal capacity", but in effect my point is correct. We are trying to preserve heat in the WATER, not really the metal cylinder. You aluminum pot has a much higher SHC, yes, and it also has much higher thermal conductivity. It's going to sink heat away from the water to the surrounding environment much faster due the the material, the thickness, and the fact that it doesn't have an insulating sleeve to slow that process.

Thanks, I forgot about that ... indeed the heat conductivity difference between aluminum and steel is about 4 times or even more (depending on the steel type). Not sure about thickness difference, it's about 2.5 mm here. However, when heat conduction is calculated, it's a bit more complex because there is also heat transfer from water to metal and metal to air ... but I will try some insulation ...

Did you measure the temperature in the (preheated) cup after the shot so I have some reference ? In my case it's 71-72°C (depending on the starting temperature) about 20-30 s after I "pull" the shot (usually around 20 ml)