I've found my bakelite heat break gasket some days ago.



New motivation doing some temperature measurement without it .



Blue wire/sensor on the grouphead is the blue graph, green wire/sensor is (placed/reaches the bottom of the piston) the red graph.

The next graphs show the pre-heating procedure: 15 pulls with a blind basket and releasing the water slowly from the group head:

After heating up the machine I let it idle for 3 hours and made several 4-5 shots (ambient temperature was 20-21 grade Celsius). Not in quick succession but 4-5 minutes in between. Boiler temperature was set at 118 grade Celsius. I shot a video of the very last pull. You can follow the temperatures on my laptop's screen:
That was one of the first of logged measures with Artisan. I have to take more, adjust sampling, smoothing etc.

Thanks for the data Gábor, and great work on your setup. What you have accomplished is super innovative!

Your brew water comes in pretty hot like mine, and then cools quite a bit throughout the shot. We are measuring surface temperature at different locations. Another possible source for the difference is different actual thermocouples and data loggers. However, the brew temperature that you logged in the video is very similar to my machine in the same ambient air condition and boiler setting. 104.8C is actually higher than any initial brew temperature I have measured but this happens fast, and I may have missed it. Then it comes down to about 99.8C to 99.0C for a couple seconds, and then rapidly cools to 92C-94C.

Your results are familiar to me, but a big difference in group surface temperature. Also compare to a Bosco Sorrento set to 1.2 bar (probably about 122C at the boiler) -- brew temperature max is 198F/92C.

I have not measured brew temperature of my Leva yet, but I keep the boiler set from 121C to 124C: I believe the brew water comes into the group cooler than the 800 because there is no flash boiling during the first 8 seconds of a flush. After that, the group begins to get hotter and I see and hear some flash boiling, and more steam. The surface temperature of the Leva rises about 3°F during a shot compared to 7°F of the 800, another indication that the brew water enters the sleeve cooler than the 800 does. In your video however, your 800 surface temperature barely moves which does not make sense to me. If the water cools from 105C to 92C, then there is a large heat transfer. I always detect a corresponding rise in the group surface temperature, measured 50mm from the bottom of the group.

I have installed a 2mm teflon spacer heat break on my 800, but I have not tested yet because I need to do a little plumbing. Hopefully I will post some results next week.

" your 800 surface temperature barely moves which does not make sense to me"

That surprised me too. But if you consider the sensor was placed at the top of the group in a position where there is no water inside. I think that's the explanation. I should take a lot more measures at different positions.

Double spring levers, both fully plumbed in. Joy! I plan to burn through some electricity and coffee over the next couple of weeks.


My teflon spacer which does not appear to make any difference in group surface temperature or warm up time.



Which makes better espresso? For B&W The Classic, I think pro 800 is a little better in bringing out sweetness. For Filicori Zecchini - Delicato, I think the Alex Leva does better, however neither are side-by-side tests, and neither are blind tests from several individuals, so not a fair test. Even a fair test is skewed by little things such as barista knowledge of machines. I am sufficiently confident to declare that they both make excellent espresso.

def wrote:Double spring levers, both fully plumbed in. Joy! I plan to burn through some electricity and coffee over the next couple of weeks.
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Beautiful and symmetrical, too!

Cool stuff Gabor! Are you planning to make this gizmo available for sale to other Pro 800 users at any point??

The modern lever group piston pressure kit has been available for two years (sold 15 kits). BUT..... the upgrade is a difficult/dangerous one. I usually ask the owners to send me the GH and I make the conversion myself for free.

Measuring temperature (as you see is still in the prototyping stage. Even no time for testing .

Does "GH" refer to the top of the group (ie, the piston/lever assembly)?