In our last post, we tested various espresso brewing temperatures and their influence on taste. Here we show you how and where the espresso brewing temperature is measured, and how you can measure the temperature of your machine at home.
The perfect brewing temperature for espresso is between 91° and 95°. For a darker roast, we recommend the range of 91° to 93°. For lighter roasts, we recommend 93° to 95° espresso brewing temperature.
Try it out at home and set different brewing temperatures to check sensorially what tastes best to you personally. But the question here is where exactly we measure, and how precise the whole thing really is.
Espresso and brewing temperature – plenty 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. As a result, there are often no clear statements about which range represents the optimal brewing temperature.
Nevertheless, or precisely because of this, we took on this topic and first examined the sensory changes and the strength or extraction. Rightly so, questions followed in the blog and in the comments on 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 must first understand the design of boilers and brew groups and their influence on temperature.
Espresso brewing temperature with thermoblock machines
A thermoblock heats the water as it flows through a tube inside the block. This means that in that moment, especially with small thermoblock systems, the inlet temperature is decisive.
Fresh tap water is usually cooler than water that has been sitting in the machine tank longer and has assumed the ambient temperature. The two water temperatures are different and need to be heated for different lengths of time. Thus, in this case, we again end up with different brewing temperatures.
We recommend always using fresh water to keep the starting point consistent. The larger the thermoblock, the fewer fluctuations you can expect. With sophisticated systems, as we see with the Decent Espresso Machine, the thermoblock performs more consistently than a boiler system. This works because the brew group is preheated by an additional heating element and numerous temperature sensors control the water supply.
With the thermoblock, measurement is done with a thermostat that often switches on and off in a 5-6 degree range. So it might, for example, start heating at 104°C and stop at 110°C. Temperature fluctuations can occur here as well.
The temperature measured in this way is the temperature in the block and not the actual brewing temperature. Depending on the design, this is then between 87°C and 93°C.
Attention – too cold brewing temperature with thermoblock if…
if you flush the group briefly before extraction. Because: before extraction, the thermoblock remains at approximately 104°C. When you start the brew and at that moment the boiler heater switches on, you'll start the brew at about 87°C and end it rather too hot. That's why we recommend flushing thermoblock machines immediately after removing the portafilter and thus before grinding, so 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 achieve the higher brewing temperature.
Thermostat and pressostat instead of PID
With 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 this is installed less frequently and usually in cheaper machines. As soon as the boiler cools down slightly, it signals the heating to heat up again. Since we basically have much more water in a boiler than in a thermoblock, boiler machines are much more consistent in temperature. The thermostat also regulates the temperature in approximately a 5 degree range.
The pressostat
Somewhat more precise, and therefore also installed in most dual boilers without PID, is the pressostat. This also passes the signal to heat to the heating element, but regulates it via pressure. With both methods, measurement is taken in the steam section of the boiler.
With a boiler typically filled with 1.5 to 1.8 liters, the temperature fluctuates slightly with both systems. With the functioning of a so-called heat exchanger, the inserted cylinder in a classic dual boiler, temperature fluctuations remain within limits. Adequate flushing before brewing also helps here to reduce the temperature of the thermo-siphon system (design of a Faema E61 brew group, in which water circulates permanently) before the brew group, so you don't extract the coffee with too hot a temperature, making it more bitter than it actually is.
The same principle applies here: the larger the boiler, the more consistency. With a 3-liter boiler, there is much more water that loses much less temperature, especially during extraction. Even in the moment when the pump pumps cold water from the water tank into the heat exchanger. The results in the cup are so much 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 with machines that have temperature control?
There are major differences between dual boilers with PID and dual or multiboilers. How these machines are structured and how they work, we discussed in detail in this article.
Dual boiler with PID
Let's take the next step in the price segment and move to dual boilers 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 with dual boilers without PID, the heating systems either heat fully or not at all. Once a sensor is installed, the heater in the boiler maintains the temperature more consistently, either through full heating or targeted heating pulses.
Measuring PID correctly
Measurement is then done in the steam section. That's why with PID machines you must always convert the displayed temperature according to the operating instructions.
An example: 124°C displayed boiler temperature can correspond to a brewing temperature of approximately 92.5°C. But always consult your machine's operating instructions, as this varies from manufacturer to manufacturer.
Even with PID devices, we would recommend flushing directly before brewing, as the water can heat up very strongly in the brew head here as well, and you thus start the brew with a very hot temperature.
Dual or multiboiler
With luxury models with dual or multiboilers, we then measure in each boiler separately. This allows very high steam temperature, independent of a differently set brewing temperature. But again, the larger the boiler, especially the coffee boiler, the more consistently you'll be able to brew.
New systems in the professional catering sector go even one step further. To achieve consistency of less than 0.5 degree temperature fluctuation during brewing, today the brew groups are actively heated to make them even more consistent. This ends up with a multiboiler machine with two coffee boilers per brew group and active boiler heating. Fluctuations are thus minimized to 0.1 to 0.2 °C and are therefore 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 outlet. Then you start a draw without coffee – importantly, you should 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 temperature significantly at the start of brewing, since the coffee is at ambient temperature in the portafilter. You'll notice a large increase during brewing.
But please don't forget to drink your coffee while you're measuring.
