We’re going to take a little programming break from coffee machines (levers, pumps, group heads) and detour into temperature calibration as this is a process I recently undertook on our machine at home. We have a La Marzocco Linea Mini on the bench. It’s a wonderful dual boiler machine (it’s been significantly customised but we can get into those details later down the track) however it has one strange quirk. Although the brew boiler is very precisely PID controlled, there is no temperature readout on the machine and the temperature is set using a simple mechanical wheel on the side of the machine. I’ve never really trusted that the wheel has been accurately set and as there is no direct relationship between the number indicated on the wheel and the temperature of the brew boiler I’ve felt the need to calibrate using an objective third party measurement system (that almost sounds like a risk advisory business!). Last Friday I was giving the stainless steel panels on the coffee machine a little scrub and accidentally shifted the temperature control wheel, so I was forced to pull out the trusty Scace thermofilter…
The thermofilter is inserted into a blind/bottomless portafilter and controls flow to simulate shot extraction with a coffee puck in situ whilst measuring the temperature of said extraction using a thermocouple. It’s an excellent device and one I find very reassuring to use as extraction temperature is one of the key brewing variables which drives the flavour of one’s coffee!