The Thermofilter performs quick, accurate temperature measurement of espresso brewing water. The Thermofilter is very useful for initial espresso machine setup, tuning espresso machines to produce optimum taste for specific coffee blends, diagnostic testing, quality assurance, and for barista training. The water temperature is measured by a type T thermocouple positioned just above the coffee cake, the point at which water temperature is most important. Measurements are obtained under flow rate and pressure conditions that are identical to actual brewing.
In order to get the performance and accuracy that you paid for, please read and understand these instructions.
The Thermofilter may give erroneous readings unless proper measurement practices are followed. The Thermofilter is also a precision measuring instrument that is easily damaged by careless handling, and storage. Examples of careless handling and storage include dropping it, bending the thermometer probe, storing an unprotected thermofilter in a toolbox or drawer with a bunch of mean and nasty hammers and wrenches that could hurt it.
Warning / Danger!!!
You can get seriously burned by hot water. This device emits a high velocity stream of hot water toward the drip tray. This stream should be collected in a suitable cup, such as an espresso or cappuccino cup to help prevent splashing of the stream against the drip tray grate. Do not allow the stream to hit you! Basically use your head and don't be an idiot.
The Thermofilter is depicted in Figures 1 to 3. The stainless steel brew basket (1) snaps into most "chopped" or "bottomless" 58 mm portafilters. The plastic insert (2) occupies the same space as an actual coffee cake and possesses similar heat capacity to ground coffee. The temperature probe (3) is potted into the plastic insert. The actual sensing element is a type T thermocouple junction that is at the very tip of the probe. Type T thermocouples are the most accurate type of thermocouple at temperatures near the boiling point of water. The mini-connector at the end of the wires fits most inexpensive thermocouple readout devices and many thermocouple dataloggers. A filter / flowmeter (4) builds pressure within the Thermofilter to actual brewing pressure, and establishes a flow rate similar to producing a "double espresso."
Figure 1. Thermofilter top view
Figure 2. Thermofilter side view
Figure 3. Thermofilter in action
B) Installation and preparation for measurement:
- The thermometer fits most "chopped" or "bottomless" 58mm portafilters, portafilters with the floor removed. Install the thermofilter into your portafilter by first passing the mini-connector and wires through the portafilter. Then snap the thermofilter into place, just like any other filter basket.
- Configure your readout device for type T thermocouples. Your readout device must be configured for type T thermocouples or you will get the wrong answer. Many readouts are shipped from their manufacturers pre-configured for type K thermocouples, the most commonly used type for general thermometry. See the instructions for your readout device in order to learn how to correctly configure your readout.
- Clean your espresso machine! Backflush the groups to be tested, removing as many coffee grinds as possible. The flowmeter within the Thermofilter is protected by a filter, but repeated exposure to coffee grinds and oils can still clog it.
Refer to the warning at the beginning of this instruction set regarding high velocity hot water hazard!
Use the manual brew switch on your machine's keypad when making temperature measurements. Temperature measurements should take place over 25 to 30 seconds, the optimum time interval for espresso extraction. Observe the readout, or log the data into your computer for further study or archiving.
To obtain the most accurate and meaningful results, follow the exact procedures when making measurements with the Thermofilter that you follow when making espresso. The Thermofilter should be installed in the group so that it becomes hot, exactly as you would do with your normal portafilters. Since you must remove a normal portafilter when dosing with coffee and tamping, you should remove the Thermofilter for a similar period of time immediately before making measurements. If your procedure includes flushing out the group immediately prior to reinstalling the portafilter, then you should do exactly the same thing just before making actual measurements with the Thermofilter. After making a measurement, remove the thermofilter from the group and flush the group to simulate clearing the group of spent grinds. By following the identical procedures that you follow when making real espresso, the temperature data that you obtain will correspond to the temperature that actually occurs during your espresso extraction process.
D) Using the Results to Improve Your Coffee:
The temperature data that you obtain will be very useful in improving your coffee and maintaining outstanding espresso quality. The best taste produced by a specific blend of coffees is temperature specific, and varies according to the makeup of the blend over the range from 195˚F to 205 ˚F. Some suggestions follow:
- Optimize your espresso machine for the blend that your shop uses: Vary the brewing temperature in your espresso machine through adjustment to the pressurestat or thermostat used in your machine. Taste the coffee produced at various temperatures. Measure and record the temperature at which your coffee tastes best. Now that you can easily correlate temperature to the best taste of your coffee, it is simple to set up new or replacement machines to produce the same temperature.
- Institute quality control checks: Electro-mechanical devices such as pressurestats change over time for a variety of reasons such as contactor wear, membrane hardening, etc. Checking the brew temperature on a daily or weekly schedule will uncover changes in temperature over time and allow you to take intelligent steps to insure high quality. Keeping a temperature logbook is a very good way to track machine performance degradation.
- Barista training: Because of design tradeoffs, all espresso machines produce different brewing temperatures when used under conditions of intermittent or constant use. Expert baristas learn to compensate for this, using various group flushing procedures to compensate for machine design deficiencies. Group flushing requirements are very quickly learned using a thermofilter. The procedures may then be incorporated into your employee training program. Using the thermofilter, experienced baristas may easily refine their flushing practices in ongoing efforts to improve their technique, or when adjusting to new espresso machines.
- Espresso machine performance evaluation: Using the thermofilter, comparisons between espresso machines are easily realized in terms of temperature stability and reproducibility. Machine selection is now more easily based on actual performance, rather than on salesmanship. Such evaluations require a systematic approach. One standardized method, The WBC Procedure for the Measurement of Brewing Water Temperature in Espresso Coffee Machines, is included for reference, in the hope that machine comparisons will be performed uniformly worldwide for all purposes.