On-Demand Grinder Design
November 16th h 2016 Author: David Schomer, When all the factors are in control, machines are clean and temperature stable, coffee is fresh, barista techniques are solid, and grinder burrs are sharp, my baristi on the bar are mostly trying to control the flow-rate of the espresso oozing into the cup. To truly capture the fragrance of the ground coffee in a shot of espresso it must flow at a very precise rate into the cup. Ideally we want to extract about one ounce of crema in 26 to 29 seconds. And, the new generation of PID controlled espresso machines have revealed the exquisite sensitivity of the process to the speed of water passing through the ground coffee. Within our range of shot times we see dozens of different espresso profiles from the same blend. On the faster side, around 26 seconds, the caramelized sugars from the Indian coffee may come forward, a little slower, 28 seconds for the ounce of crema, and Ethiopian coffees may dominate the cup with a chocolate/umami. Shots that time out less than 25 seconds, “fast pours” are sour astringent at Vivace and shots that take longer than 30 seconds, “slow pours” may be hollow or have a bite to them. After 28 years of brewing espresso I am more fascinated than ever with the beauty and complexity of this method. For the expert baristi all over the world this is not big news. They have also learned that with the new temperature stable PID espresso machines, the flow-rate is what we must control to capture the fragrance of the coffee into the cup. And, we all struggle to control that factor. To control the flow-rate the grinder must produce the same particle distribution, and quantity of ground coffee each time we grind for a shot. Right now there is no grinder being made that can do this. Essential to artisan extraction is the practice of grinding each shot freshly. Commonly called “on-demand” grinding. At Vivace we have been grinding to order since 1988. This practice is now common to baristi from New Zealand to Taiwan, trying to make the finest shots possible. Although we now have stable espresso machines, the world-wide artisan espresso revolution does not yet have a grinder. Many on-demand grinders have been rushed to the market. They are simply modified, old style Italian grinders with the dosing hopper removed from the front. But to grind each shot individually, with a perfectly uniform grind, and dosage accurate to 1/10th of a gram, requires the grinder to be completely redesigned for this purpose. Many companies have placed a cone , or a vertical chute, where the old Italian dosing hopper used to attach to the grinder. In these machines the ground coffee must travel horizontally through some sort of chamber to the delivery cone or chute. This creates a machine with pre-ground “chambered-coffee” trapped within it. You cannot control the flow rate of the espresso if any ground coffee is trapped within the grinder. The on-demand grinder must dose straight down into the PF without the powder touching any metal surface. This DRM grinding head clearly shows the chamber that traps about 6g of ground coffee on the way to the doser. Here we see the Anfim SP 450 without the doser cone. This grinder is being sold as an on-demand grinder but chambered pre-ground coffee equals almost 18g. The chambered coffee affects extraction in two ways. The first risk is ground coffee sitting in the machine, warm, and going stale. When it sits it also loses moisture. A dryer powder needs a finer grind. So, if it goes into your shot the dryer powder will offer less resistance to pressurized water, and the shot time speeds up. (Our window for a great espresso right now is 26 to 30 seconds to extract under one ounce (25ml) of crema. If the shot takes longer, flavor can go hollow, bitter, or sour. However, caffeine content is higher. The fast pours, under 25 seconds, are sour astringent, and the customer doesn’t even get the full caffeine. We always pitch the fast ones, serve some of the slow ones if they get the proper hang…at any rate my baristi are throwing out shots because the flow rate is too fast or too slow). The current crop of on demand grinders also face major difficulties getting the powder to the PF with out altering the composition between fines and the coarse flakes. Here is a micro=photo of the complete powder mix from a conical burr set. Fines are evenly distributed within a matrix of larger particles. As the coffee slides down into the PF static may affect its particle distribution. The static pulls the fines out of the tumbling mix because they have less mass, they are lighter than the bigger flakes.. What we need is true fidelity to the original mix of fines and coarse particles exiting the burrs. Here is what happens as ground coffee is allowed to spray into the doser. Static electricity had caused finer particles to cling to the metal. This is a micro-photo of the particles that were clinging to the cone. Note it is predominately the fines. In conical grinding systems any static-electricity field the powder passes through traveling to the PF will affect the fine particles more than the larger flakes. (Conical burrs first grip the bean in the large fins and squeeze until it shatters, this produces particles of all shapes and sizes, including the smaller ones, called “fines”. Then, the bean is sheared to a consistent flake size with the finer teeth on the bottom half of the conical burr. But the fines slip through. Flat burr grinders are the choice for many baristi and grinder manufacturers like Mahlkonig, precisely because they feature more consistent flaking of the bean. It is true that conical burrs, producing fine particles, can make flow-rate control more difficult. However, the fines contribute much more flavor and a heavier mouth-feel in the cup and have always been our choice at Vivace despite flow-rate challenges). In the above picture you can see what happens if the coffee sprays out of the chamber, the fines separate and cling to the cone. And, lacking fines, the espresso pour speeds up, and the coffee thins out as well. To solve this the powder requires a gentle consolidation coming out of the chamber. This way the coarse flakes trap the fines in their original matrix. Static can’t separate out the fines when they are imbedded gently in the larger flakes. Consolidated coffee does not cling to the cone. Here is a simple cross-wire gate to prevent spraying coffee grounds by consolidating the powder with gentle back-pressure. Mazzer likes this solution and we employed it on the DRM as you can see. In theory, the wires should slow down and consolidate the coffee powder gently. However, with our roast, it worked poorly. True we did not have as many cling problems, but the stream of ground coffee could back-up making cakey blocks of ground coffee drop into the PF. If the coffee backs-up, the residence time of the powder in the burrs increases. The beans re-grind and become finer. Flow-rate control, our number one concern, is again destroyed when the shot seizes up. And, you can’t simply adjust for a coarser grind, each dosage of the powder will be different. After a couple of years we gave up on the cross wire gate. Back-ups were occurring way too often. We had another interim solution fail, and then arrived at this, the chain gate. ( Btw, if you are wrestling with a Mazzer caking on you, tear out the wires, and just hang a strip of scotch tape in front of the port, and see how you do. If it’s still cakey, softer tape for less resistance…) At Vivace we tried this stainless steel cable chain gate on the entry to the doser cone. Sized at 1.5mm links separated by 2mm beads, it makes a perfect curtain to just consolidate the grind particles a bit, but not too much. Using the chain gate, we never have cakey coffee, but we are getting some cling on the cone as summer turns to autumn. We are running a fleet of 14 grinders and man do my baristi have to dance to try to maintain a perfect flow-rate while these issues affect the ground coffee consistency. They must always be conscious of the condition of the chambered, ground coffee within the machine. If it has sat too long, the barista must purge 6g out of the chute. And, if we get any cling we need to brush it out of the cone very quickly. We can’t lose the fines or the pour speeds up and thins out. They have a teeny cling brush. But the damage is done to the powder even if you brush the cling into the PF because the distribution of the fines in the mix has been altered. Looking at the pour under the bottomless PF will reveal the imbalance in the powder by having the pour favor one side or the other. With perfect powder the pour is always dead center under the PF. You know it’s beginning to remind me of the dance we used to do to get the machines to be more temperature stable. I remember we called it “temperature-surfing”. And the materials used in machine manufacture included porous brass they used for the PF and the group head. That stuff would trap oils and go rancid quickly. We had elaborate tool kits including green scrubber pads to clean the brass every 40 minutes of operation. Well, this grinder thing is beginning to feel like those old days before PID and stainless steel. We are getting tired of the dance to overcome equipment that is not made to grind-fresh for each shot. We all rosed our vices then, demanding temperature stable machines. It is time for artisan baristi all over the world to demand a grinder designed for us. However, if I am going to complain it is better to bring something to the table. I have found a design, the Sette (made by Christian Etzinger for Baratza) is a home grinder that solves the chambered coffee problem and the particle drift problem perfectly. Here we see the jet of ground coffee shooting out of the bottom of the grinding head in the Sette. Christian has his delivery mechanism attached directly to the bottom of the conical-burr set. But the coffee doesn’t tumble out it is impelled by an engineered disc with indented ramp areas. The coffee shoots out in a jet. The blades consolidate the particles and accelerate the stream of coffee so the metal collar it passes through cannot affect it even if it picks up a static charge. Making coffee on this grinder I always hit my flow rate. An experience I would like to have at Vivace. He has told me that he will come out with s commercial grinder, made to grind by the shot, in 2017. An on-demand grinder must also produce the exact dosage with each shot. Timers that run the machine for a set period of time are not accurate enough. To get a consistent dosage amount the grinder must shut off when the desired dosage weight has been reached.
After a couple months using the Baratza Sette grinder at home I see a slow shift towards a coarser grind occurring. (After several months I have been backed into the finest setting the machine can produce.) Kyle, the ever helpful owner of Baratza said they have noticed this as the burrs break in over time.
Currently, even at the very finest setting, I’m barely maintaining a 25 second extraction. Kyle says he has a kit to allow a spacer to be installed beneath the burr set. That will work. My only question is why isn’t the spacer installed before shipping the grinder?
Also, there is definitely chambered coffee within the grinder. Not very much, but a 4 g minimum purge is required in the morning to get that first shot to pour well. It makes sense, because any grinder used for on-demand grinding will have broken beans trapped within the burr set.
My recommendation: run the motor until all coffee is expelled each evening to have truly fresh grind in the morning.
The Naked Truth-reading your pour
The bottomless, or naked, port-filter is especially well named. Because there is no hiding: the entire integrity of the espresso program, from grinder burr sharpness, barista technique, coffee freshness and roast, and machine calibration is on display. There is no hiding using this porta-filter. And of course the closed, or traditional port-filter, is a huge metal surface contributing rancidity to your cup if it is dirty. So the naked porta-filter is the only choice for truly great espresso.
Above is an extraction on Nuova Simonelli’s T3 of our Vita blend. The grinder is the DRM mixed burr. The color density can be read and offers 100% fidelity to the actual flavor and strength of the shot. I have never seen a pour without some lighter spoking in it, but here it is very faint. ( Good luck getting an extraction to look like this). But the less whitish color and the more rich brown showing, the more flavor you have extracted from the ground coffee.
Whitish colors indicate this extraction was about 5o% efficient. Shot timing is OK, about 26 seconds for the one ounce shot. However, light color means about 1/2 the flavor potential of the ground coffee was destroyed during brewing or grinding the coffee. This color indicates a weak extraction but does not pin point the problem. It could be dull grinder burrs, stale coffee, or temperature drift during extraction.
This pour is timed at 20 seconds for one ounce, a fast pour. Lighter color may in this case accompanies a very sour flavor which I think is citric acid.
This pour timed out at over 30 seconds, a slow pour. Dark color overall indicated burned coffee compounds and the flavor might be hollow, bitter, or sometimes sour, but not citric-acid sour. Stream is favoring the right-hand side as we look at it, which is generally not good.
This pour times out at 27 seconds for the one ounce shot but is off balance. Offset stream indicates a crooked pack, or bad distribution of ground coffee before packing. On the left is blacking, indicating water flowing too slowly on that side and “burning” the essential flavor compounds, , on the right it is lighter indicating water flow is too fast on that side of the extraction.
Novmber Pro Barista Class
Hello expert baristi…we are planning our next Pro Barista class for mid November. Contact Jes at email@example.com to get a spot. We are limited to eight students, as always. Here is a picture of the last class to graduate, with students from New Zealand and Korea.
Home Grinder- Baratza Sette, a review
Kyle Anderson and engineer Christian Etzinger have made an on-demand grinder so revolutionary that I predict it will influence grinders made to grind per-order for espresso for years into the future.
The two design elements that are allow this teeny machine to brew great espresso are both known, and I admit a bit of a mystery to me. I do know this produces a beautiful full flavor extraction but I don’t know why…but of course I have a theory.
In the past I have tested many conical grinders and formed the opinion that if you grind the coffee too quickly, say 20g in less than 8 or 9 seconds, you get a thin, watery extraction much like a flat burr machine produces turning the burrs at 900 rpm. The effect was very consistent looking at Mazzre Kold machines, turning large conical burrs that would grind the 20g shot in about 4 seconds. Always thin espresso…Compak grinding a little slower made espresso that was a little thicker and more flavorful. And my choice at Vivace, the DRM mixed burr system grinds 20g in about 14 seconds and produces the thickest most flavorful shots I have ever encountered. You can “read” the shot under the basket of a naked port filter. Take a look at the Sette shot made on a Breville Dual Boiler:
This is a damn good pour. Ok ready? The Sette turns a 40mm steel conical burr (made by Etzinger) at 1100rpm and grinds the 20g shot in six seconds! It should be thin and watery and it is not. (I love it when a “sacred cow” is slain and my theory is out the window). The only difference I can point to for this very superior performance is that the design drives the upper, or female, part of the burr set with the motor and all other grinders that I am familiar with drive the lower, or male burr. I honestly have no idea why this would make such a huge, huge difference in viscosity and flavor intensity but it is the only real difference I can point to. (Or maybe the Etzinger burr is extremely superior but I lean towards the former explanation).
OK, what is the other innovation I am so excited about? As you know if you have made more than one shot on a PID espresso machine and can taste at all, flow rate is the Holy Grail. To control flow rate you must control the dosage to +/- 0.1g of ground coffee in the basket and you must have a uniform particle distribution in the powder coming into the port-filter. In all grinders on the market today the powder is exposed to static electricity on the way to the PF, and they all have trapped, pre-ground coffee in the stuck in the machine between shots. The static pulls the fine particles out of position in the powder to a greater degree than it affects larger, heavier particles, resulting in uneven fidelity to the original particle compositional matrix. You cannot move the powder through any apparatus without screwing up the particle distribution. When the fines are moved out of the mix, and stick to the cone or whatever they are traveling in, the shot speeds up. Flow rate cannot be controlled if the powder is constantly affected by static.
The other enemy of flow rate control is the pre-ground chambered coffee. Any ground coffee stuck in the machine between shots changes it’s moisture content immediately as it sits. It desiccates due to motor heat, or it becomes more saturated in environments with very high humidity. Either way pre-ground coffee will have a different flow rate than fresh ground. I cannot tell you how vexing this is on the bar. Controlling the fines, and accounting for the gawd-damn chambered ground coffee makes my baristi crazy. They end up throwing out shots and doing an elaborate dance featuring cling brushes and chain gates to try to manage the powder. Any time we have a few minutes between customers, or they change the grind, they must purge out the approximately 6g of ground coffee sitting in the machine. It is wasteful.
This design features a bare minimum of pre-ground chambered coffee, maybe 1% of a 20g shot (0.2g) so its negligible. Also it has an impeller that turns at 1100rpm and the ground coffee makes a jet column, passing out of the grinder so fast the fines are not affected by static on the way to the PF. The speed means very little time that the coffee is exposed to the air and no particle migration. Here is the view peeking up into the impeller and burr set. Showing the bottom of the burr with a thin coat of ground coffee.
I have never in my life has such perfect control over flow rate as the Sette gives me, and it makes wicked good espresso. By far it is the best home grinder I have ever used.
The machine features infinite, stepless grinder adjustment and will deliver the same powder at the same setting perfectly due to the features I described above. It can be set for drip to French Press easily.One caveat, the fine control ring migrates slowly to a more coarse setting when you operate it. I am thinking Kyle and Christian will fix this asap but for now I put a little piece of tape on the ring to hold it.
Also, this machine is loud. I mean loud, if you have a cat it will bolt out the door and it will never come home again. I hate noise but I still love this little grinder for the shots I can make.
Vivace Pro Barista Training
Finally pro baristi from all over the world can learn the secrets of Vivace extraction techniques and latte art. Nuova Simonelli has supported this program with the installation of a new, modifies T3.
First classes are
June 22, 23, and 24th.
July 27, 28, and 29th
For more information visit espressovivace.com/training or email firstname.lastname@example.org
Breville of Australia has created a home espresso machine they call the Dual Boiler. It makes a fine shot, really fine, and costs about $1300
The company, located in Australia, offered me this machine to check out recently. I had been using LaMarzocco’s GS3 for years but it is oversized for my teeny place, (and it was very loud in a buzzy, leaf blower way), so I agreed to check this out. Of course, I was not expecting much for $1700…delightfully I was spectacularly wrong. This machine makes better shots than the GS3.
To start they have a PID controlled heating element in the group head and coffee boiler, a feature I had only found in the $20,000 Nuova Simonelli T3 machines. (Which I immediately purchased for Vivace). With that temperature stability comes the unique, super heavy cone of crema hanging off the coffee basket on the naked porta-filter. Espresso is much stronger than extractions without the heated group head.
The machine is very user friendly, operates on 110V power, and is easy to fill with water and empty drain tray. It runs fairly quietly and heats up quickly. The steamer woks well with a tip and power balanced perfectly to roll the milk in the 1/3L pitcher. Brewing temperature, pre-infusion time, and steam pressure are fairly easy to program. It even has teeny wheels that you can project under it with the turn of a knob. (OMG, really?)
It is possible to make shots as good as the T3 but it is not quite as consistent, and as always, your dependent on a good grinder. Pictured below is their grinder. It had trouble holding onto a consistent powder in my place, but it is better than any other home grinder I have tested. The burr turns slowly, grinding 20g in about 23 seconds and if you can keep it consistency dialed in, will produce full flavor shots, comparable to my commercial DRM mixed-burr grinders.
OK here we go again…Like a moth to the flame I will try once more to introduce a processor controlled water formulator into Espresso Vivace’s system to enhance flavor of our espresso.
Of course you remember the first time I contacted Cirqua company and installed their formulator’s into our shops (2006). The science was solid because the minerals used by water scientist David Beeman had a fantastic effect on espresso coffee. Varietal flavors became distinctly stronger, with no metallic edge or astringency, and body and mouth-feel were enhanced. However, the machines they made…not so good. After months of break downs and no support from Cirqua, I ripped all their crap out in a fury promising never again….
I could not stand it….it is not my way to back off espresso improvements so here is the formulator being installed. After a week of this coffee it is as good, or better than I remember it to be.
What happened was last year I was reading about some nice baristi in Europe getting together with a chemical engineering graduate to try to identify minerals than enhance coffee flavor. That got me thinking about it again so I tracked down David Beeman who has been working on this continually for 20 years at least. (We worked together on initial formulations sometime in the early ’90’s). He wisely gave up on his own company, Cirqua, and has been picked up by Global Customized Water as their water scientist while they handle manufacturing, distribution, and maintenance on the machines. So far, so good….I am on a three month trial to see if the formulator is reliable. The espresso we are serving has never been close to this good.
Latte Art Tutorial
Cruising around YouTube I was reminded that my pioneering course “Caffe Latte Art” was out of date, and had already been ‘jacked and posted for free anyway on the site. We currently have much better information, particularly on milk texturing. So Teal Allan, Brad Langsdale, myself, and editor Corey Higgins, got together a quick video and posted on YouTube at no charge. The old DVD will be pulled off the market very quickly.
I am very appreciative of the enthusiasm and joy with which latte artists around the world have embraced free poured latte art. This is my little thank you…
Single Origin Espresso at Vivace
Starting in January of 2015 Vivace will serve single origin espresso at both of our indoor espresso bars.
With the potential of espresso close to perfection, due to advances in equipment, I have decided that Vivace can now begin offering different coffees as straight espresso and Americano. Well… I suppose we would make you a Ugandan Exende macchiato if you wanted one….