Mahlkonig E65S gbw grinder review

BY CLAY BUSH

Welcome to our first grinder review!

Many grinder reviews focus on the usability and aesthetics of the grinders.  Here at Pillar, whilst we acknowledge these are important qualities, we focus on the burr geometry and the grinders ability to perform under duress. Burr geometry is important to us because we see it as the link between roast density, and the machines set pressure and flow parameters. Many in the industry don’t have the means or inclination to test a grinder worth beyond taste, however here at Pillar, and Bush and Bush coffee systems, we hold the view that the more you understand grinders the better the result you can achieve with them.

However, an understanding of a grinders ability is not always easy to quantify. To this end, we use our own investigative methods and calibration tool. So there may be some new concepts in this article. These concepts are based around our most important metrics here at The Truth, those being roast density and puck density. It’s a little-known fact in the industry, that puck density can be used to classify grinders. This will be our first public foray into this arena. So if you’re getting a bit lost, you’re not alone. It is our intention to discuss burr geometry in future editorials but for now, this article will provide broad brush strokes for these new concepts.

The legends at Brewtech lent us both the E65S GBW and E80 to test, however, the interest in the industry was also great to test these grinders so our time to get acquainted was minimal. Less than 24 hours in fact before it was passed on for the next roaster to trial.  It also meant we could only focus on one, so we chose the E65S GBW, and have peppered any extra commentary on the E80 throughout this review.

So, with little time, we rolled up our sleeves and got to it. 

E65S Grind by weight function (GBW)

Firstly, we checked the grind by weight function under normal load. This function is limited to the E65S gbw. Our testing highlighted an extreme deviation of only .2 of a gram. Which is quite impressive, all the while achieving clump-free coffee. So in this regard, it lives up to the hype written on the tin. My assumption for only using this GBW technology on the E65S is because the E80 has larger cutters, and the ability to grind 22grams in less than 4 seconds. That’s very fast; however, this fast grinding comes at a cost which is the accuracy of weighing. In our testing, the variance on the E80 was up to .7 of a gram at an outlier, but generally less than .5 gram. For this speed of grinding it’s not such a great deviation, it remains in the normal range of grinders we have tested with this grind speed. The upside is that with such a fast grind speed, Mahlkonig could lower the RPM speed of the E80 in the future. By lowering the RPM the grinder will grind slower and therefore give more accuracy with weighing. In this case they may be able to use the GBW function on the E80 as well. Regardless, it was a sensible decision by Mahlkonig to perfect the smaller E65S cutters first.

After checking the grinders under normal operating conditions, the next step was to “flog” them and see at what point the grinder loses consistency. This is a “Saturday morning simulator”, if you will, to see how it performs in a high-speed setting. With limited time, we only did this with the E65S in order to check the GBW function under stress. All grinders have a breaking point. This breaking point is highlighted by exceeding its duty cycle. (for an understanding of duty cycles please see our getting to know your grinder article) To exceed the duty cycle is to use the grinder under greater load than it is engineered to withstand. This duty cycle is a roundabout way of declaring what size of a café the grinder will suit. Ultimately if you exceed this duty cycle under normal operation, it is not the fault of the grinder, more so, your error for buying the wrong size grinder for your café requirements. So under normal circumstances, you should never be in this scenario. However, I tend to test grinders outside of their duty cycle to see how bad they actually get. Some grinders hold up well outside their duty cycle and others fall off a cliff.

So to determine this we basically ground off 1kg of coffee in about 10-12 minutes. With a duty cycle of 5on 15off for the E65S, we definitely exceeded its recommended operating parameters. 

When we started the temperature of the beans in the hopper were 28 degrees. The first grinds came out at 36 degrees in temperature. That’s about normal and consistent with the Mazzer super jolly, which has a similar size burr (64mm). So far so good. By the fourth dose that had climbed to 41 degrees. Still not outside the norm. As we continued to flog the grinder and exceed the duty cycle, as expected, the grinder housing started to heat up. (there is a temperature reading on the grinders display to illustrate this) At the same time, the resultant ground coffee also heated up. This too is normal. The important thing is how high above 36 degrees does the ground coffee pile climb. This is what we mean when we say “how bad do things get,” The E65S peaked at 44 degrees. And held it despite further heating to the chamber. 44 degrees sounds high but is not out of the ordinary for this burr size. Lower temperatures are only usually achieved through larger burrs. Because our environmental factors were stable, this had little effect on the puck density or run speed of the shot (for an explanation of puck density, click here). The flow rate of the heated grind particles in the puck ran 15% faster through the espresso machine. This is not a great deviation considering the increase in ground temperature, as there was little deviation in puck density, by association. There is little deviation in the GBW function. At this time the grind by weight function only fluctuated by .2 gram which is very impressive. 

This 15% deviation in run speed, also happened to coincide with potential hopper weight issues. Most bean hoppers have a weakness in their design, where the hopper shape can change the weight that the beans transfer to the burrs. This change in burr weight can affect the grind consistency. Unfortunately, due to time restrictions, we couldn’t determine where the level is on the e65 and e80. But like most grinder hoppers we assume this is around 150 grams as this is where the grind will begin to shift. So, like most grinders, when the beans in the hopper reduce, and you can see the inner cone, best to top up your beans. Even with this slight deviation in run speed, the grind by weight was still accurate. So if you stay across your grind and hopper weight, the GBW function should remain consistent.

Heating up

The e65 will get “cooked” in a fast-paced environment. So this grinder is good for probably a 25kg café, running 7-days a week. Greater volumes will require the e80, or a change in process to ensure the rest time between grinding is maximized. 

Burr Geometry

Here at Pillar, and Bush and Bush coffee systems, we acknowledging that a coffee can be made with any grinder, however there are circumstances where each grinder can be best utilized. Broadly speaking, we identify grinders into one of two main categories. 

• Old school burr geometry (Mazzer, Anfim, Fiorenzato)

• New school burr geometry. (Mythos, Mahlkonig peak) 

We haven’t discussed this difference in burr geometry in our editorials as yet. And as this is the first time we have introduced these concepts, we will give a basic conceptual understanding here, with a view to fleshing out these concepts further in future editorials. 

As their name suggests, new and old school grinders are classified by their particle distribution philosophies. Old school Burr geometry heralds from a time of second crack coffee and excessive fines. They use fines migration through the puck to choke flow and therefor build pressure in the puck. This often comes with a cost of over-extracted or heavy flavours from the same fines that generate the pressure. 

New school Burr geometry on the other hand, create minimal fines, and in respect to the particle distribution curve, are usually represented by a higher mode. This makes them suited to 1st crack coffee with lower flow rates. Whilst they may often result in a lower TDS, a higher condensed mode, and fewer fines, generally results in a cleaner taste. 

So what is the e65? Both the e65 and e80, by our classification, are new school grinders.  

So who will benefit from this grinder?

New school grinders like the e65 and e80 will benefit from machines with lower flow rates, and lower pressures. This means that machines that have smaller restrictors like .6 or .8 will benefit from this grinder. Whilst higher machine flow rates can be used, they will most likely produce a lower TDS, resulting in a weaker coffee. Roasters who roast light with higher roast densities will also benefit from the e65. Personally, I would also run faster shots with these grinders. If for instance, you use a standard 20grams in 40ml out in 30 seconds, with this grinder I would use the same recipe of 20g in and 40g out, but with a faster run time in the vicinity of 26-28 seconds (faster shots are a characteristic of these new school grinders, (assuming your roast density is on the high side).   

By classification, that means whilst this grinder could be used for a second crack coffee or machines with excessive flow rates, it may not have an optimal result.  

And finally, how did it taste? 

Because the e65 is a new school grinder, it will naturally have a cleaner taste with a lighter body. This grinder is very much a first crack specialty grinder with a similar taste profile as the Mahlkonig peak and extraction principles like the Mythos. So if light roast coffee is your jam, I would definitely give the E65S GBW or E80 grinders a go!

Drink much Coffee 

Cheers 

Pillar x Bush and Bush coffee systems.