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 spectrum from 91° to 93°. For lighter roasts, we recommend 93° to 95° espresso brewing temperature.
Try this at home and set different brewing temperatures to check sensorially what tastes best to you personally. The question here, however, is exactly where we measure, and how precise the whole thing actually is.
Espresso and brewing temperature – plenty to discuss
Since I've been dealing with the topic of 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 a lack of clear statements about what spectrum represents the optimal brewing temperature.
Despite this, or precisely because of it, we've tackled this topic and first examined the sensory change and the strength or extraction. Rightfully, the following questions came up in the blog and in the comments on the YouTube video:
- where do you measure the temperature?
- how constant 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 on thermoblock machines
A thermoblock heats water as it flows through a tube within the block. This means that 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 for a while and has reached ambient temperature. The two water temperatures are different and need to be heated for different amounts of time. Thus, we end up with different brewing temperatures in this case.
We recommend always using fresh water to keep the starting situation constant. The larger the thermoblock, the fewer fluctuations you can expect. With sophisticated systems, like 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 heater and numerous temperature sensors control the water supply.
With the thermoblock, measurement 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 actual brewing temperature. Depending on the design, this is then between 87°C and 93°C.
Caution – too cold brewing temperature with the thermoblock if…
if you flush the group shortly before extraction. Because: before extraction, the thermoblock remains at around 104°C. When you start brewing and the boiler heater switches on at that moment, you'll start brewing at around 87°C and finish at too high a temperature. 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 too cold rather than too hot.
Procedure for brewing with thermoblock machines
- Remove portafilter
- Flush group briefly, short water extraction
- grind and fill portafilter
- extract
After point two, the thermoblock heats up quickly and you'll achieve the higher brewing temperature.
Thermostat and pressostat instead of PID
On 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 rather rare and mostly installed in cheaper machines. As soon as the boiler cools down a bit, it signals the heater to heat 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 installed in most dual boilers without PID, is the pressostat. This also passes the message to heat to the heater, but controls this via pressure. With both methods, measurement is done in the steam area of the boiler.
With an installed boiler of usually 1.5 to 1.8 liters of filling capacity, the temperature fluctuates slightly in both systems. With the functioning of a so-called heat exchanger, the recessed 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-syphon 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 should be.
Here too, the basic principle applies: the larger the boiler, the more consistency. With a 3-liter boiler, there's much more water present, which then loses much less temperature, especially during extraction. Even at the moment when the pump pumps cold water from the water tank into the heat exchanger. The results in the cup are thus 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 on machines with temperature control?
There are major differences between dual boilers with PID and dual or multi boilers. How these machines are built and how they work, we discussed in detail in this article.
Dual boiler with PID
Let's take the next step up 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 heater. Often, heating systems in dual boilers without PID either heat fully or not at all. Once a sensor is installed, the heater in the boiler keeps the temperature more constant, either through full heating or targeted heating pulses.
Measure PID correctly
Measurement is then done in the steam area. That's why with PID machines you must always convert the displayed temperature according to the instruction manual.
For example: 124°C displayed boiler temperature can correspond to a brewing temperature of approximately 92.5°C. But always consult the instruction manual of your machine, as this varies from manufacturer to manufacturer.
Even with PID devices, we'd recommend flushing directly before brewing, as the water can heat up very strongly in the brew head here too, and you'd start brewing at a very high temperature.
Dual or multi boiler
With the luxury models with dual or multi boilers, we then measure in each boiler separately. This enables very high steam temperature, independent of a differently set brewing temperature. But here too, the larger the boiler, especially the coffee boiler, the more consistently you'll be able to brew.
The new systems in the professional gastro area go even one 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 ends up with a multi boiler 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 thus negligible.
Measuring espresso brewing temperature at home
To measure the brewing temperature on your own machine, you need a temperature probe, which you insert deep into a portafilter outlet. Then you start a extraction without coffee – it's important that you always do this with a hot portafilter. There are also portafilters with built-in thermometers. We use these, for example, for our tests, because this also creates resistance against the pump.
If you want to do the measurement with coffee, the water naturally loses significant temperature at the beginning of brewing because the coffee is at room temperature in the portafilter. You'll notice a significant increase during brewing.
But please don't forget to drink your coffee in all the measuring.
