Prufrocker: The Blog

Circa 2016

I flew out to the Mazzer factory in Venice a couple of weeks ago. The connection was made because I mentioned to Francesco from Mulmar (Mulmar are the UK Mazzer distributor) that Mazzer might explore the Mazzer ZM design for espresso purposes knowing how popular a multipurpose low retention grinder is becoming in the UK... Read more »

by  |   |  Coffee Science, Equipment


I flew out to the Mazzer factory in Venice a couple of weeks ago. The connection was made because I mentioned to Francesco from Mulmar (Mulmar are the UK Mazzer distributor) that Mazzer might explore the Mazzer ZM design for espresso purposes knowing how popular a multipurpose low retention grinder is becoming in the UK market. A couple of hours later Francesco calls me and says ‘pack you bags, we’re going to Venice.’ Swoon! So me and Francesco and the R and D team at Mazzer set to work testing an 83mm Titanium burr for espresso. More about these tests and the trials on the Prufrock bar in a few weeks once we’re done on the trials. In the meantime…consider this is a purpose built filter grinder.

What is so entirely intriguing about this design is that it answers the exact contemporary brewbar questions that have been at the forefront of our thinking (and everyone we are influenced by) on brew-bar management in 2016. Efficiency and sustainability and improved customer service.

Customer service benefits; let’s cover this issue first. If this design was a luxury car and actually had a clock,  then that’s all you could hear when you operated it. The clock ticking. It’s the quietest grinder I have ever operated so quite simply you won’t deafen your customers. It’s low profile so you can see them too.

Next, and linked to customer service is that this design massively reduces mess. The point here is customer perception of quality. The thing that has most possessed me about this new design is that the throat of the grinder is not part of the grinder, so what minimal static builds up in this area is removable, which means the retention (that grinder throats all have) is no longer a contributing factor in the grind retention because the grinds all fall into the container that latches directly at the base of the barrel directly below the blades so there is no area; no passage at all for grinds to collect. That means retention is down to 0.4g

This in itself is impressive but it’s actually about to get even better still because the tiny recess beneath the blades is closing up so no grinds can collect in this area at all. As such the retention will drop to 0.2g and suddenly we are at the absolutely negligible area where you can round down the residue to zero because we are literally talking about the weight a single bean. Hence the need to purge the grinder between cups is alleviated and waste drops to zero.

To put this in perspective, if prufrock does a 5g purge between coffees on our brewbar and we only make about 30 a day, this is still 54.75kg a year. Also worth noting that brewbar coffees all come in at about £20+ per kg as at Prufrock we are only putting forward the three highest scoring coffees per week to go on the Brew Bar menu so we’re talking about 1000+ quid a year in purgings. Hopefully you purge less than 5g in your cafe or maybe you already don’t worry too much but with this grinder, trust me, you really don’t need to think about it. And better still, you don’t need to reweigh.

So let’s say you are operating a pre-portioned dose brewbar using those so hard to find little tins they sell at Tinware Direct (Thanks Tom Hopkinson for the link). You can dose these on the money and grind and brew when a customer arrives. The system we are looking to pilot with the ZM Filter Burr Grinder is where our cashier grinds the coffee at the point of sale literally as the customer orders and then as the coffee heads down to the brewbar with the ticket so the brewbar operator is then in charge of extraction with water, not dosing, weighing and rinsing.

Look back at the  Prufrock Efficiency Structures: For four cappuccinos, it takes a quality barista 3 min to make the whole lot themselves. But it only takes 40 seconds or less for a barista of quality to prepare the espresso shots. This tells you single-shot making is 10 seconds per customer, milk pouring and steaming is 35 seconds per customer (which in itself is terribly slow). Then there’s the average prep time at Prufrock for a pour over: 5min. We tested this at Prufrock the other day at a staff meeting. The getting the coffee out of the bag, the rinsing of the paper and the getting of the brewing equipment was taking 4:15 seconds and the Scott Rao pour-over method using our Uber Boiler was 45 seconds. See the Scott Rao V60 method below. He blogged about this the other day too.

So the ZM with its incredibly low retention can get this timing here down to 3min. Throw in an a pre-rinsed paper and already loaded V60 waiting for you on a shelf and the sort of pourover that has a precise brew ration, weighed in water and an agitated bloom phase is possible to produce at the rate of 1 per minute allowing 5 seconds to literally put the coffee into the V60 from the pot and then 10 seconds to put the brewing equipment in place and tare the scales. 500% increase in efficiency friends! Hard to beat and 17 000 times more accurate and consistent than this system which whilst being kind of legendary is pretty naff (IMHO) with its 70um filter; the fine filtration equivalent of a Land Rover.

This element of the workflow redesign we are contemplating I quite appreciate also because the cashier is also in a position where they are at times under employed so they can in turn match the workload of the poor latte artist down the end of the bar. Throw a volumetric single cup brewer into the mix with this workflow and you are in a position to see you one cup brews coming out of the same workflow as you espresso based drinks. Something we shall also be piloting the the incredible Dalla Corte MIna machine over the next few weeks. More about this later.

Next fairly irresistible element to the ZM is that the build quality is incredible. This has been a frustrating element to a lot of coffee equipment in the last decade or so as designs have become more and more popular and manufacturers have tried to keep lead times tighter, it is inevitable build quality has dropped off. Baristas have sought to take ownership of this issue with quite brilliant ideas like Matt North’s solution for burr alignment. To summarise he gets a white board marker and inks up the burrs. Fines up the grinder until the blades touch. Opens up the grinder again to see where the ink was removed and props up the fixed burr to sort out the misalignment. For me I find this quite challenging and Matt tells me that the copper tape that his amazing Bristol cafe Full Court Press use is prone to shifting out of place. The simplest alternative to this is a build quality that can get parallelism so perfect that the barista armed with his/her foil tape is not called upon to correct imperfections in manufacturing. The idea of truing a wheel seems to translate across perfectly and this is certainly a concept that resonates with baristas so the idea has certainly found some traction.

Mazzer state that the alignment of the ZM is better than 20 um. To put this in perspective the width of a piece of foil is 12um. Here’s some technical specifications for sticky tape putting it at 38 um. No good either. Throw in adhesive tape and this pushes the width of a piece of tape out further out than the maximum tolerance of the ZM grinder. Skeptical as I tend to be, I tested the parallelism of the ZM anyway and please note I have prototype 9. Literally the 9th grinder in this design they made so many improvements have been carried out since this design and every time I applied my aluminium foil tape to improve the alignment on one side of the grinder, the whiteboard marker ink would be removed from the opposite side. This satisfied me that the parallelism was close than the width of my tape and thus, better than I have ever encountered.

Most of all what excites me about this design is the dial. Prufrock held a competition using this grinder last Thursday and big congratulations to Jacob Thue (the guy who fabricated Prufrock’s RO system), his company is called 94 degrees if you wanna get in touch. So we had 30 baristas playing on a grinder which has a dial that requires 4 complete rotations between one cup V60 and a 4L batch brew. This was challenging for the baristas to locate their grind setting but also an incredible opportunity to massively zone into a specific grind setting.This extreme precision in setting the dial is achieved through the back burr being the moving burr rather than the front. So there is a much wider region the blades can operate in and the back burr is moved using a geared brass thread.

The major payload you get from the back burr being the moving burr is that this is the easiest to clean grinder I have literally ever used in my life and for me, this is still the main distinguishing factor between a good or bad cup…clean equipment. Three screws and the blades are there waiting for you and throw the miracle of an easy to clean grinder into sharper light and you see the front burr carrier has the screw places in a scalene triangular shape meaning you can only replace the burr carrier in the same position which is just that little bit of attention to detail you want from your lovely grinder manufacturer.

I recall Ben Kaminsky saying in London in 2012 during his coffee-shots workshop that he had visited Mazzer and stated, with their technology ‘they could build basically anything in their factory’. I say touche to this comment and am delighted to say that with this ability at their disposal, they are applying their know-how into exactly the same direction we were hoping to proceed.

 

Fine

_____________________________

Prufrock’s interpretation of The Scott Rao Pourover Method

1.Temperature 89+deg C (in the slurry at 1min) so 94deg C from the Uber, 97deg C from a pouring kettle

2.Dose 14-16g/250ml as needed

3.Time: split: 20 seconds pre-wet with 3ml per gram of coffee. Then after agitating the coffee in a N-S-E-W-NE-SW-NW-SE shape (you know-Union Jack shape) pour all the rest of the water in 25 seconds. NSEW stir then one 360deg stir above coffee bed at drawdown

4.Grind: See Moleskine. Scott says ‘Grind as coarse as possible’. Love this advice.

 

Please note, this method requires a larger sized cone. For a one cup V60, use the 02 size. For a one cup Kalita, use the 185 size because all that water will be in there in 45 seconds. The total contact time here will still end up being 2:30 or so, but the point of this method is that it’s more temp stable, promotes more even extraction and after 45 seconds, you can start making another one…or stack some dishes. The labour duration is calculated separate to the the contact time.