In our last post, we tested various espresso brewing temperatures and their impact on taste. Here, we show you how and where to measure espresso brewing temperature, and how you can measure your machine's temperature at home.
The perfect brewing temperature for espresso is between 91° and 95°C. For darker roasts, we recommend a range of 91° to 93°C. For lighter roasts, we recommend an espresso brewing temperature of 93° to 95°C.
Try this at home: set different brewing temperatures and sensorially check what tastes best to you. The question here, however, is where exactly we measure, and how precise the whole process is.
Espresso and Brewing Temperature – A Lot to Discuss
Ever since I've been involved with coffee, brewing temperature has always been worth a long conversation. Different brewing systems and brew group designs significantly change the consistency and influence of temperature. Thus, clear statements about the optimal brewing temperature range are often lacking.
Nevertheless, or precisely because of this, we took on this topic and first examined the sensory change and the strength or extraction. Rightly, the following questions arose in the blog and in the comments of the YouTube video:
- where do you measure the temperature?
- how consistent is such a machine?
- how precise are these measurements?
To answer these questions, we first need to understand the design of boilers and brew groups and their influence on temperature.
Espresso Brewing Temperature in Thermoblock Machines
A thermoblock heats water as it flows through a tube within the block. This also means that for small thermoblock systems, the inlet temperature is crucial.
Fresh tap water is generally cooler than water that has been in the machine's tank for a longer time and has adopted the ambient temperature. The two water temperatures are different and require different heating times. Thus, in this case, we end up with different brewing temperatures.
We recommend always using fresh water to keep the starting conditions constant. The larger the thermoblock, the fewer fluctuations can be expected. With sophisticated systems, as seen in the Decent Espresso machine, the thermoblock performs more consistently than a boiler system. This works because the brew group is preheated by an additional heater and numerous temperature probes control the water supply.
Measurement in a thermoblock is done with a thermostat, which often switches on and off in a 5-6 degree range. For example, it starts heating at 104°C and stops at 110°C. Temperature fluctuations can also occur here.
The temperature measured here is the temperature in the block and not the effective brewing temperature. This then again lies between 87°C and 93°C, depending on the design.
Caution – too low brewing temperature in thermoblock, if...
...you flush the group just before extraction. Because: before extraction, the thermoblock stays at approx. 104°C. If you start brewing and the boiler heating switches on at that moment, you will start the brewing at approx. 87°C and end it rather too hot. Therefore, we recommend that you flush thermoblock machines immediately after removing the portafilter and thus before grinding, so that the thermoblock can heat up again. Thermoblock machines are generally rather too cold than too hot.
Procedure for brewing with thermoblock machines
- Remove portafilter
- Briefly flush group, short water draw
- Grind and fill portafilter
- Extract
After step two, the thermoblock heats up quickly, and you thus reach the higher brewing temperature.
Thermostat and Pressostat instead of PID
In almost all boiler machines without temperature control (PID), the temperature is regulated via a mechanical thermostat or pressostat.
The Thermostat
Let's start with the thermostat, as it is rarer and mostly found in cheaper machines. As soon as the boiler cools down a bit, it tells the heating element to heat up again. Since we generally have much more water in a boiler than in a thermoblock, boiler machines are significantly more consistent in temperature. The thermostat also regulates the temperature within an approx. 5-degree range.
The Pressostat
Slightly more precise, and therefore installed in most heat exchangers without PID, is the pressostat. This also signals the heating element to heat up, but it regulates this via pressure. In both methods, measurements are taken in the steam area of the boiler.
With a built-in boiler, usually with a filling volume of 1.5 to 1.8 liters, the temperature fluctuates somewhat in both systems. When it comes to the function of a so-called heat exchanger, the integrated cylinder in a classic heat exchanger machine, temperature fluctuations are limited. Sufficient flushing before brewing also helps here to reduce the temperature of the thermo-syphon system (design of a Faema E61 brew group, in which water constantly circulates) before the brew group, thus preventing the coffee from being extracted at too high a temperature and becoming more bitter than it should be.
The principle also applies: the larger the boiler, the more consistency. A 3-liter boiler contains a much larger volume of water, which then loses significantly less temperature, especially during extraction. This also applies at the moment when the pump draws cold water from the water tank into the heat exchanger. The results in the cup are thus significantly more consistent. With the Basilea with PID and a 3-liter boiler, we measured a temperature fluctuation of less than 0.4 degrees – this is world championship level!
Where do we measure on machines with temperature control?
There are significant differences between two-circuit machines with PID and dual or multi-boilers. We discussed in detail how these machines are built and how they work in this post.
Dual-circuit machines with PID
Let's take the next step in the price segment and move to two-circuit machines with PID. Now we no longer measure mechanically via pressostat or thermostat, but via a sensor. This allows precise measurement and precise control of the heating. Often, the heating systems in two-circuit machines without PID either heat fully or not at all. As soon as a sensor is installed, the heating in the boiler keeps the temperature more constant, either by full heating or by punctual heating impulses.
Correct PID measurement
Measurement then takes place in the steam area. Therefore, with PID machines, you must always convert the displayed temperature using the operating instructions.
An example: 124°C displayed boiler temperature can correspond to a brewing temperature of approx. 92.5°C. However, always refer to the operating instructions of your machine, as this varies from manufacturer to manufacturer.
Even with devices with PID, we would recommend flushing directly before brewing, as the water can heat up very strongly in the brew head here too, and you would thus start brewing with a very hot temperature.
Dual or Multi-boilers
With luxury models featuring dual or multi-boilers, we then measure in each boiler separately. This allows for a very high steam temperature, independent of a differently set brewing temperature. However, here too, the larger the boiler, especially the coffee boiler, the more consistently you will be able to brew.
The new systems in the professional catering sector even go a step further. To achieve consistency of less than 0.5 degrees temperature fluctuation during brewing, brew groups are now actively heated to make them even more consistent. This results in a multi-boiler machine with two coffee boilers per brew group and active boiler heating. This minimizes fluctuations to 0.1 to 0.2 °C, making them negligible.
Measuring Espresso Brewing Temperature at Home
To measure the brewing temperature on your own machine, you need a temperature probe that you insert deep into a portafilter spout. Then, start an extraction without coffee – it's important to always do this with a hot portafilter. There are also portafilters with built-in thermometers. We use these, for example, for our tests, as they also create resistance against the pump.
If you want to take the measurement with coffee, the water will, of course, lose a lot of temperature at the beginning of the brewing process, as the coffee is in the portafilter at ambient temperature. You will notice a large increase during brewing.
But please don't forget to drink coffee in all the measuring.
