Nicely done and very helpful!

excellent work dennis! thanks for taking the time to undertake & publish. personally i think your empirical evidence suggests that thermal stability of the cremina group is incredibly good for such a small group.

i have developed temp probes that plugs directly into a usb port and you can download an app from apple store and it records the data in an excel file. i need to refine it though as i have the probes housed in 5mm diameter stainless steel tubes for durability. as a result there is too much thermal inertia - it takes too long for a change in temperature to travel through the housing, so the probe does not respond quickly enough from room temperature up to circa 200F, taking almost 10 seconds to respond

your fine probe solves this problem, but how many times can it be used before it wears out? i am trying to develop a solution that is accurate, durable, non-destructive (other than a PF basket), and easy to set up and achieve accurate results with.

On a side note... leaving the machine on for a couple hours and then just walking up to it and pulling a shot did not work at all on my '96 (small group head) Pavoni Pro. Overall, the Cremina '67 is a LOT more temperature-stable and it seems to me that this is the biggest difference between those two machines.

Also, for me, pulling 4-5 shots in a row works on the Cremina. Granted, #4 and #5 are nowhere near optimal but still good enough to serve when you have a few friends around, especially when cooling the PF in between pulls. Unthinkable on my old Pavoni.

So I'd be a little careful transferring the information gained in this test to other machines, because I know from experience that the technically almost identical Pavoni behaves very differently with regards to stability of temperature. I have never handled a Sama or Elektra, though.

That said, I'd be very interested in the differences between the '67 and newer models, though. Especially thinking of possible improvements on the '67 like the teflon-seal Doug talked about.

One little thing I've often asked myself and would really like to see tested is whether it makes a difference to leave the portafilter in or take it out in between shots. I imagine taking it out could bring down the temperature of the group head ever so slightly, possibly improving those walk-up-to-the-machine-shots.

dergitarrist said

Especially thinking of possible improvements on the '67 like the teflon-seal Doug talked about.

I would like to get hold of one of those teflon seals too. Maybe time for another Orphan Espresso order...

Yes, my limited experience with the Pavoni also showed that it overheated if left on. A while ago, though, someone tested this with a newer Pavoni and found it less prone to overheating.

This is a great help, although I'm not totally sure how to apply the numbers to the old cremina. Do you think 165 degrees at the bottom of the bell would equate to a 200f pour?
I'd really like to accurately check the temperature of the bell all the time. If you could disassemble the Taylor 9840N, so that perhaps you could tape the probe of the thermometer (I'm assuming that it is a small metal bit that takes the temperature which is housed in the steel tube) to the bell and have wires running to the readout somewhere else?

Do these wires end in a little probe that can be taped, and if they do, can you pull them out of the hollow thermometer tube? (Photo taken from the E61 thermometer instructions)

John, old Cremina and new Cremina group head is exactly same. I had old Cremina and it behaved temperature wise same as new one. You can pretty much use all the info.

I am awaiting new temp strips Eric found and should have them next week. I'll try them and post the results...

Londinium Espresso wrote: your fine probe solves this problem, but how many times can it be used before it wears out? i am trying to develop a solution that is accurate, durable, non-destructive (other than a PF basket), and easy to set up and achieve accurate results with.

Thank you. I really can't say how long the probe will last, but I don't expect durability to be problem. Time will tell. These probes are not that expensive though.

Nice work

I have a similar 'in-basket' a probe that's lasted 100's of measurements.

One caveat : use an extension between the probe and the meter. Eventually coffee will traverse the length of the probe and could leak into the meter. Orient the extension so the extension connector is higher than the probe's.

tekomino wrote:I am awaiting new temp strips Eric found and should have them next week. I'll try them and post the results...

Dennis,
I think those new strips with the lower temp targets will be a big help in hitting target temps for shots 2, 3, 4, ... On my Cremina, if I have any hint of color on the 90C strip before preinfusion, the temp shoots right past my target. Same thing happen on yours?