Gaggia Classic E24 – Why is it so special?

About this Video

• Video Title: Gaggia Classic E24 – Why is it so special?
• Channel: Espresso Hackers
• Speakers: One (unnamed)
• Duration: 00:15:25

Introduction

This video reviews the Gaggia Classic E24 espresso machine, focusing on the reasons behind its high quality and improved features compared to previous models. The speaker conducts several tests and shares data to support their claims regarding temperature stability and other improvements.

Key Takeaways

• Brass Boiler Advantages: The E24's brass boiler offers superior temperature stability compared to aluminum boilers found in earlier models. The increased weight and density of brass contribute to better heat retention and a more consistent brewing temperature. It also mitigates galvanic corrosion.
• Improved Temperature Stability: The E24 demonstrates significantly improved temperature stability during brewing, resulting in a smaller temperature fluctuation in the coffee puck. This is partly due to the larger boiler volume (25% increase) and a more precise thermostat.
• New Thermostat: The E24 features a new thermostat that activates at 103°C and shuts off at 104°C, offering a more precise temperature control than previous models (103°C and 107°C). This contributes to the improved temperature stability.
• Minor Drawbacks: Despite improvements, the E24 retains some minor drawbacks, including a 15-minute auto-shutoff (Eco Mode), a tight space for cups under the portafilter, and a plastic OPV (15 bar in Europe, 9 bar in the US). These are easily modifiable.
• Temperature Surfing: The video details how to "surf" the temperature, adjusting brew timing based on the machine's heating cycle and the desired coffee temperature. The speaker provides temperature readings at different stages of the heating cycle to guide this process.

Pre-2014 Gaggia Classic models used an aluminum boiler and a brass group head, along with a solenoid valve, an adjustable brass OPV, and rocker switches. The E24 uses a brass boiler and group head, eliminating the issues caused by the different metals. Later models (post-2014) experimented with stainless steel and aluminum boilers with Teflon coatings before returning to the brass boiler in the E24. The rocker switches and adjustable brass OPV were replaced with push buttons and a less durable, non-adjustable plastic OPV in some intermediate models, issues addressed in the E24's design (though the plastic OPV remains).

The speaker compared the temperature stability of their Gaggia Classic E24 to their 2006 Gaggia Classic model. Using a thermocouple type K and consistent brewing parameters (19g in, 40g out in 25 seconds), they measured the temperature in the puck at different points in the brewing cycle. The E24 showed significantly less temperature variation: a mere 1.5°C difference between maximum and minimum when brewing at the "light off" point (97.2°C initial to 97.6°C peak), compared to larger variations in the older machine using either PID or the standard thermostat. The E24 also showed minimal fluctuation (3.1°C difference) when brewing at peak temperature (118°C boiler temperature), and 3.7°C when brewing at the "light on" point. The older machine showed 4.3°C and 5°C variations with PID and thermostat, respectively. The E24's temperature stability was described as "amazing" and "super stable," even exceeding the performance of their Rancilio Silvia with PID.

The "boiler gate" refers to a period where Gaggia introduced a new aluminum boiler coated with a Teflon-like material to prevent scaling and galvanic corrosion. However, this coating began to flake off, requiring Gaggia to replace many machines and boilers. This negatively impacted Gaggia's reputation, leading them to switch back to a fully aluminum boiler with coating and, eventually, to the all-brass boiler found in the E24.

The speaker suggests using the machine's heating cycle to "surf" the temperature for brewing. Here's what he outlines:

• When the light goes off: This indicates the boiler has reached 103°C. The water will continue to heat due to inertia, peaking at 118°C. If you brew at this point, the temperature in the puck starts at around 97.2°C, drops to 96.1°C, and then rises to 97.6°C, with a total variation of only 1.5°C. This is presented as an excellent starting point. He also notes that if you start brewing right when the light goes off (at 103°C in the boiler), the temperature in the puck is around 94.2°C and only fluctuates by 2.4°C over the brew.
• When the light goes on: This signifies the machine is ready to brew, but the boiler temperature is around 104°C. Brewing at this point results in a starting puck temperature of 98.7°C, dropping to 95°C, with a 3.7°C difference between max and min.
• At the peak temperature (118°C boiler): If you brew when the boiler reaches its peak, the puck temperature starts at 102.1°C, drops to 99°C, with a 3.1°C difference. He notes this is quite hot and potentially suitable for fermented beans, but generally too high.

He emphasizes that the temperature in the puck is more stable when brewing occurs shortly after the light goes off or on, rather than waiting until the boiler reaches its peak. He also mentions that the Gaggia Classic E24, after about 10 minutes of preheating, can produce a stable brew with a 2.4°C temperature difference even if started at the first opportunity after the light goes off.

Essentially, he's suggesting that by observing the indicator lights and understanding the temperature inertia, you can time your shot to achieve a desired and stable brewing temperature without needing a PID controller, especially if you're brewing within the 10-minute preheating window.

At 10:16, the speaker is explaining the implications of the temperature fluctuations for "temperature surfing," which is the practice of timing your shot to coincide with the most stable temperature range. He's providing specific timeframes and temperature ranges based on his experiments:

• "light goes off, you have maybe 14 seconds to increase a bit the temperature by 1.5 degrees the temperature, the initial temperature in your puck."

  • Explanation: When the heating element turns off (light goes off, boiler at 103°C), the temperature in the puck doesn't immediately drop. There's a short window where it remains relatively stable or even slightly increases due to residual heat. He's saying that if you start brewing around this time, you have about 14 seconds to work with, and the temperature at the start of your shot (in the puck) will be around 97.2°C (as seen in earlier tests) and might increase by about 1.5°C during that initial period before it starts to significantly drop.

• "Then you'll have up to 22, 25 seconds to start extracting between 98.7 and 101.2 degrees."

  • Explanation: This refers to the window after the "light goes on" (boiler at 104°C) and before the temperature drops too much. He's suggesting that if you aim to start your extraction when the machine is in this ready state (light on), you have a period of about 22 to 25 seconds to begin your shot. During this time, the ideal temperature range in the puck would be between 98.7°C and 101.2°C.

In essence, he's giving practical advice on when to pull your shot based on the machine's indicator lights to achieve the most stable and desirable brew temperature without needing complex equipment. He's translating the raw temperature data into actionable timing advice for the user.

You are correct to point out that seeming contradiction. The speaker does express reservations about brewing when the light is on, but it's more nuanced than a simple discouragement.

Here's the breakdown:

• General Recommendation (Light Off): The speaker generally prefers and recommends brewing when the light goes off. This is because, as he shows in his tests, this point (boier at 103°C) leads to the most stable puck temperatures with the smallest variations (e.g., 1.5°C fluctuation in one test). He explicitly states, "if you start to brew when the light goes off, or 3.1 if you start at the peak temperature, or 3.7 if you start when the light goes on. It's even better than the 4.3 that I achieved with my Gaggia Classic with PID or 5 degrees with the thermostat." This clearly indicates that starting when the light goes off results in the least temperature variation.

• The "Light On" Scenario (Nuance):

  • He does mention that when the light goes on, the boiler is at 104°C, and the peak temperature the machine achieves due to inertia is 118°C.
  • His test when the light was on showed a starting puck temperature of 98.7°C, decreasing to 95°C (a 3.7°C difference). This is higher than the variation seen when brewing at the "light off" point (1.5°C).
  • He also notes that brewing at 118°C boiler temperature (which is higher than the "light on" temp) is "super hot. Maybe if you have a fermented coffee, you may give it a go, but I think it's too hot." This suggests that the higher temperature ranges, generally associated with the "light on" and peak periods, can be too hot for many beans.

• The 10:16 Statement Context: The statement you highlighted ("Then you'll have up to 22, 25 seconds to start extracting between 98.7 and 101.2 degrees") likely refers to the potential range if one chooses to brew during that phase. It's not necessarily an endorsement, but rather an observation of what the temperature is during that window. The 98.7°C is the starting point he measured when the light went on, and the 101.2°C is a point he mentions later in the context of stabilization.

In summary: The speaker strongly favors brewing when the light turns off for maximum temperature stability. While he acknowledges that brewing when the light is on is possible and provides temperature data for it, he implies it's generally hotter and has more temperature variation, which is less ideal for most coffees. The 98.7°C to 101.2°C range is what he observed during that phase, not necessarily a recommendation to aim for it.