BY NOW I’M SURE YOU ARE FULLY AWARE THAT THE SYNESSO ESPRESSO MACHINE DELIVERS INCREDIBLY STABLE WATER TEMPERATURE. THE ACTUAL SPECIFICATION IS +\- 0.75 DEGREES FAHRENHEIT ACROSS THE LENGTH OF THE SHOT OR, IN LOCAL CURRENCY, THAT’S AROUND +\- 0.4 DEGREE C. GREAT FOR THE COFFEE! WE CAN PROGRAMME OUR SET POINT AND CONFIDENTLY BEGIN PULLING SHOTS KNOWING THE WATER TEMPERATURE WILL BE PERFECTLY OPTIMISED FOR OUR COFFEE.

There is one potential, but significant problem though. From time to time, we may need to verify the calibration of this extremely precise setting. For instance, we may need to do this if an electrical component in the PID control system is replaced. Standard metrology (the science of measurement) testing protocols state that the tools and testing procedure should be ten times more precise that that of the parameter which is under test. That’s certainly not going to happen in our case, but it does illuminate our need to develop a test procedure that is as accurate and repeatable as practically possible.

Enter the Scace — a tidy and well-made tool which, if used correctly, has the potential to suit our purposes. When I say ‘used correctly,’ I really mean that the tool needs to be used in a way that absolutely minimises the introduction of uncertainties due to the way we use it. The following is my procedure for using the Scace to calibrate the infusion water temperature on a Synesso Espresso machine.

Before jumping straight in, it is very important to thoroughly clean the group to be tested. Any coffee grinds which enter the Scace will cause a partial blockage and cause our readings to be fully bogus. (The opposite of fully sik!) After cleaning the shower screen, dispersion block and collar seal, you can check that you’ve been successful by running water into a white cup and looking for any coffee grinds.

The next step is to place the Scace in the group under test and allow it to temperature saturate. Run 30 seconds of water into the drain tray and start a timer. After exactly 5.0 minutes, start the first 30 second test shot. Press the hold button on your temp meter at exactly the 15 second point. This temperature is subtracted from the current set temperature for that group and becomes our test result, hopefully a small positive or negative number with at least one decimal place. Allow the group to rest for exactly 5.0 minutes and carry out a second and then a third test.

By averaging our test results, we produce a correction which we now add to the current offset in the machine. After another 5 mins to allow the machine to stabilise at the new and more accurate temperature, we carry out our test again to verify that we have a correctly calibrated group temperature.

Here is one I prepared earlier…