The Weber Key espresso grinder, MK2 version, is a high-quality single dosing grinder from Weber Workshops. It costs around 2200 Euros ex-warehouse in Germany! A hefty sum of money, though no surprise. At Weber Workshops, the exquisite BIRD French press also costs over 300 Euros.
Every Weber product is an investment, and every product we've looked at so far is well-made and of very high quality. And that also applies to the Weber Key!
And while the grinder does many things well, not everything convinced us. As you will learn in this review, we believe that the Weber Key does not perform its main task well: The taste performance in espresso preparation did not convince us.
Quality and Impression
The Weber Key Mk2 in your coffee corner is a statement of high quality, aesthetics, and willingness to invest. It differs visually from other espresso grinders on the market and also sets benchmarks in craftsmanship. However, it is striking that Weber nowhere communicates the exact material of the housing. At least, we could not find this information.
Technical Specifications
- Dimensions: Depth 248mm x Width 109.2mm x Height 349.6mm
- Weight: 9 kg
- Power supply: 90-240V (globally compatible)
- Power: 350W max
- 83mm conical burrs from Mazzer with TiN coating
- Variable speed range from 30-150 RPM
The grinder is available in white and black, and the wooden elements can be customized.
Weber has revised the grinder compared to Model 1. The current model has higher torque and is thus supposed to be able to grind even lighter beans without problems. We also had no problems with the grinder seizing up, even with very light roasts.
The Magic Tumbler has also been improved, enlarged, and equipped with a different lid. However, we cannot say exactly what improvements were made here, as we only looked at the MK2 model. This review is therefore based only on the examination of the Weber Mk2.
Noise Level Weber Key Mk2
The Weber Key is the quietest espresso grinder we have measured so far. We measured only 67 decibels. This is a very low value, considering that many grinders exceed 80 decibels.
As a rule, espresso machines are quieter than grinders. The Weber Key is one of the few grinders that is even quieter than some espresso machines when grinding beans.
Retention, Speed, and Construction
In terms of construction, the Weber Key resembles a large hand grinder. The 83mm conical burr set is set in motion via a central axis. The Weber Key also shares the low retention with a hand grinder. We measure a total of only 0.2 grams of absolute retention. This is really very, very little, especially since we did not find any permanent retention at all. We have never had that! The small temporary retention of 0.2 grams is technically already halfway into the portafilter. It gets stuck in the Magic Tumbler: partly on the wire agitator and partly on the rim of the tumbler. Again: This is almost nothing. But it is still unpleasant because these 0.2 grams sometimes fall out of the grinder at a later point and then dust the surface around the grinder.
Due to its design and low retention, the grinder is extremely consistent and reliably dispenses the inserted amount of coffee from shot to shot. Thanks to the grinder's design, we can also quickly dismantle and completely clean it without effort. However, the low retention makes this rarely necessary.
Like a hand grinder, the Weber also has a slow grinding time, which is naturally related to the low RPM. If we put 18 grams into the grinder, it takes 25 seconds to grind the coffee completely at 90 RPM. If we fill the hopper completely and grind for 10 seconds, we get an output of 8.1 grams. This makes the grinder the slowest in the category of all coffee grinders tested so far. This test is always performed with the same espresso and set recipe.
The grinder also owes its slow grinding speed to the fact that the ground coffee does not heat up during grinding. We measure an average temperature of 30.92 °C for five consecutive shots, which we take every 20 seconds. This means there is no risk of sensory properties changing due to the heating of the coffee grounds.
Particle Distribution and Espresso Performance
In the most important category of our test, the Weber Key shows an anomaly that leads to a negative test result. After seasoning each grinder, we take samples for comparative particle size distribution analyses. For this, we set each grinder to the Apas Espresso with the same recipe and take a sample (T4). Then we set the grinder to Ristretto (T5) and Lungo (T6) and then return to the original Espresso (T7). We send these samples to the Zurich University of Applied Sciences (ZHAW). The particle distribution is measured at their Coffee Excellence Center.
In recent years, we have examined over 60 grinders and compared them, aligning the particle distribution curves with our sensory perception. Before testing the particle curves, we were already surprised by the taste of the espresso shots. We felt that our coffees, which we know very well from daily brewing, were remarkably off-target. They tasted poorly structured, the acidity was rather unpleasant, and there was a lack of balancing sweetness.
This result matched the particle size distribution measurements. The Weber Key delivers a very, very wide main peak of over 447 micrometers! For comparison: In the past, we talked about a main peak from 320 micrometers being wide and leading to less structured cups and less clarity in the coffee.
A wide main peak means that a grinder delivers ground coffee of imprecise particle size. With the Weber Key, we mainly find many particles in the coarse secondary range of the main peak. There is a pronounced right flank.
This is particularly evident in comparison to other grinders we have currently measured. The Weber Key shows a particle distribution that we otherwise only know from very inexpensive espresso grinders. And no, that has nothing to do with the conical burrs. See, for example, the comparison with the Niche Zero in the graphic above.
Extraction Comparison
To better understand the extraction behavior, we carried out several series of measurements. We performed extractions with both a medium roast (Apas, Brazil) and a lighter roast (Limontitla, Mexico) using the same recipe and measured the TDS. As a comparison grinder, we used a relatively inexpensive grinder, namely the Eureka Specialità.
The extractions and strength of the Specialità were significantly higher for both coffees. Especially with the darker roast, the extraction yield was on average almost two percent higher! The TDS was on average 0.7% higher. This is possible due to the more uniform grind of the Specialità and the lower number of boulders (coarse particles).
A high extraction yield is desirable for high-quality coffees!
With the lighter roast, the difference was less pronounced, but still significant. Here too, we are talking about roughly 1.2% more extraction yield!
Conclusion: Who is the Weber Key MK2 the right grinder for?
The Weber Key is of high quality. We see little reason why the grinder shouldn't last several decades on a home barista's counter. Its low noise level also expands its range of applications. As the quietest grinder measured to date, the Weber Key cuts a fine figure alongside very quiet machines like the Sanremo You or Maro Model 1 in offices or doctors' practices, as well as in households that value aesthetics and high quality.
The retention is exceptionally low, and the consistency of the grinder is very good. Changing recipes is also easily possible, although smaller steps would be desirable. It is important to be aware of the slow speed. The Weber Key Mk2 is one of the slowest grinders on the market!
While the importance of speed is a matter of taste, we rate the actual espresso performance of the grinder as limited. Especially with lighter specialty coffees, we were often disappointed by the espresso results. The huge main peak in the particle distribution is responsible for this. We only know such a broad main peak from very inexpensive grinders. As a result, our espressos often tasted disharmonious, less sweet, and could not compete with the results of other, even significantly cheaper grinders. What often led to unpleasantly dominant acidity with lighter roasts can have a positive effect on some darker espressos. We would therefore rather see the Weber Key Mk2 in the range of darker roasts. This it shares with a grinder like the Pico from La Marzocco.
Since the Weber Key Mk2 did not convince us in terms of taste, this review also concludes on a disappointed note. The high-quality workmanship and the reputation for creating great materials precede Weber Workshop. In the test of the Weber Key Mk2, these expectations were not met for us.
