Espresso Vivace Roasteria
David Schomer’s Blog | Cutting-edge espresso technique and equipment review

Equipment-direct dosing grinders

Dear Reader,

 

After many efforts to assist in the manufacture of a new grinder with no Italian-style dosing hopper (read: air/coffee mixing device that contributes annoying clacking sounds to the espresso bar) I decided to just outfit my own DRM grinders with Mazzer cones. (I use the mixed-burr model with the rubber drive belt.) A few months into it I will cautiously announce success.

 

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The trick is to manage the powder to avoid micro-particle migration as it tumbles into the chute. The powder coming from the DRM mixed burr does contain substantial micro-particles along with larger particles. These micro-particles give the espresso crema a heavier body and more intense flavor, but if  the powder is allowed to “float” for even a fraction of a second after it exits the grinder port, static will draw the micro-particles to the edges of the “cloud” of ground coffee ruining the extraction.  The trick is to provide just the right amount of back pressure on the stream of powder as it exits the grinder port so it tumbles into the chute in a manageble, cake-like consistency.  Too much back pressure and it is too hard of a cake, not enough back pressure means it sprays into the chute and micro-particles stick on the sides.  I had to try several different designs of gate systems on this port to achieve just the right powder. Even among my eighteen DRM grinders different gate designs are required due to the individual characteristics of each grinder.   And, I suspect that throughout the year we may experience the need to change the gate configuratiuons to accomodate different weather.  Complexities upon complexities…I love this.

 

The advantages are many: 

1. We see better espresso due to a more homogenous powder.  Forcing the powder through my gate system breaks up the natural lumping that occurs in fresh coffee as it is  pushed out the port.  Flow rate inconsistencies are also minimized in the pour. 

2. We can go faster on the bar.  Grinding is now hands-free for the barista. It takes some getting used to….installing the empty porta-filter into the mount before hitting the grinding switch changes the rythym of the barista but my staff is unanimous that it is a much faster system once you get used to it.

3. No gawd-damn clacking sound in my shops.