Prufrocker: The Blog

The IQ Grader

Here are a couple of issues that summarise for me the dilemma of the independent cafe trying to work out where to position itself on the quality vs quantity continuum. Mythos vs Peak grinder battles…and the should you just serve it conundrum? Here’s how to approach these issues working from the viewpoint of our GM Matthew (UK... Read more »

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Here are a couple of issues that summarise for me the dilemma of the independent cafe trying to work out where to position itself on the quality vs quantity continuum. Mythos vs Peak grinder battles…and the should you just serve it conundrum?

Here’s how to approach these issues working from the viewpoint of our GM Matthew (UK Roasting Champ and number 3 in the World Roasting Championships in Shanghai) who commented recently as he tries to structure a plan for our future, ‘you guys have already done the best’ (kind of him to say this), ‘so what we need to do now is be the smartest.’ Now of course I really want to do the best and be the smartest. Is that even possible?

If we apply this rationale to the question of what grinder to buy…the one that is going to give you the best tasting espresso and be the easiest to use, (and out of fairness to the Peak, we won’t bring up the subject of ease-of-cleaning) we come up with this: The best grinder will make the nicest tasting coffee. Tim Wendelboe says this of the Peak I’m told by the UK Mahlkoenig rep Oli Bradshaw. The smartest grinder will allow a barista to discard fewer shots so they can ‘just serve it’ with impunity knowing that their shots will all taste good and meet a scoring prerequisite. Maybe the best grinder will be both easier to pinpoint extraction targets, and will taste the best over the broadest shot time range. That would be nice. The smartest grinder will be the most ergonomic and the least wasteful. But we want both; best and smartest. Build quality and consistency let us down with both designs so how do we choose? If you’re not contemplating purchasing either design, this post should give you insight into how to structure your decision on spending huge sums of money on equipment.

What I observe in spite of recent impressive grinder research extolling the benefits of brewing coffee on outdoor market stalls in the North Pole, the best selling grinder at the moment sells the best probably because it heats beans up, allowing it to deliver a dose that is consistent; something we’ve asked for for years and I observe as a trainer that this is what people want most. Maybe it’s dosing consistency is more down to its very narrow gap between the burrs and the edge of the barrel, or it could be the rather flimsy teflon clump crusher. What ever the Mythos’ specific innovation that has brought about a resolution of +-0.3g, dosing consistency is good for business because it make workflows faster. Scales can go out the window (don’t go that far), so we’ll put this increased dosing consistency in the smartest grinder category.

The smartest and best barista when dialling-in has a plan: Establish a scoring prerequisite. Make sure this coffee can reach this score. Then they will know what they can expect from their coffee and know the recipe range they need to keep this coffee inside of to keep it servable. I’d say best practice in modern espresso is better compared to a game of softball than a game of darts. It’s not just a case of shooting at the bullseye, it’s more a case of ‘bunting the ball into the field of play and running your little heart out.’ The reason the Mythos has enjoyed such outstanding sales figures over the last year or two is that the state of speciality coffee was very much ready for the smartest category of grinders because many of us were exhausted and broke from the quest of best. Also a morning QC protocol actually has some relevance with this grinder rather than the heating and cooling issue from practically every other grinder on the market that means recipes that were identified as best in the morning can be adhered to for an whole shift with confidence…

Apply a QC protocol to older equipment and you get problems. Then we train people to use a calibrated scoring system but…rather than being able to replicate recipes that were performing well during the morning grinder calibration, we train them in analysis ‘on-the-fly’ and teach concepts like a system for reducing extraction during busy periods knowing with hot grinders we tend to see extraction increasing: go a notch coarser at lunch time; reduce the temperature. You remember this old conundrum right? My coffee tastes nice in the morning and terrible in the afternoon? Interestingly we see an increase in extraction as we go hotter and colder. With this in view, I do question why the grinder research didn’t explore the behaviour of coffee grinders in the warmer region of coffee grinding where (I’m speculating…confidently) 99.999% of the world’s grinders operate. 

Waste reduction in grinders brings you back to the smartest category. The ‘Just serve it’ approach will certainly reduce waste. If this approach is prioritising customer experience over quality then Matt Buchannan will at least find some peace.

In my Tamper Tantrum with Steve he made me realise something I’d not really twigged to properly: some coffees are harder work with than others! When this occurs, he expects baristas just to work harder. With all my efficiency structures work recently, I forget that that baristas might actually enjoy this struggle. We took a step forwards in waste management and understanding of materials with some insight from barista Amanda Lo, certainly one of the smartest baristas we’ve had. Why don’t we just write down the shot time range? she says. A case of less espresso-darts and more coffee-softball.

The best and smartest Barista award goes to s/he that knows already that good shots and efficiency are easier to achieve on some days than others with some coffees than others. Then they couple this understanding of their raw materials with an empathy for what the customer wants from them. Speed or precision from one customer to the next. So I’m almost agreeing with Chris Baca but I’m saying ‘just serve it’ to some customers. Particular if irate NY bloggers so set against unsolicited coffee information are in the queue. Don’t just serve it to everyone and don’t be in the position of not knowing what your coffee tastes like anyway. Blaming the grinder is no excuse. A new grinder is no solution. They’re flawed, they are still flawed but you the barista can be flawless.


Introducing the I-Q Grader exam to get those cogs turning and to make sure we aren’t taken in by the hype..


I-Q Grader (An exam to plot yourself on the smart vs best continuum. Some questions have more than one answer, some have none. Answers next post.)


  1. A coffee is pulling at 18.5%. You score it at 2.5s (on the WBC score sheet: average-good). You’re dosing 18-34g and the timer says 28 seconds. There is some astringency in the shot and it is imbalanced towards bitterness and light bodied. Your brew water is 94degc.

Do you?

a.) drop the dose and grind finer

b.) decrease the brew water temp

c.) coarsen the grind and increase the brew water volume

d.) consider changing the grinder blades


  1. You shot tastes sour and thin bodied.

Do you?

a.) increase the dose and grind finer

b.) decrease the dose and grind finer

c.) keep the dose the same and grind finer

d.) keep the dose the same and grind coarser


  1. Your shot reads 20.5% extraction yield and you’ve pulled an 18-38g brew ratio in 30 seconds. You find some sweetness but there is some mild astringency.

Do you?

a.) fine the grind and reduce the dose

b.) coarsen the grind.

c.) coarsen the grind and reduce the yield.

d.) get yourself a new Linea PB


  1. You taste bitterness and astringency on a 20-40g brew ratio and a 36 second shot time

Could this be caused by?

a.) over-extraction

b.) under-extraction

c.) channelling

d.) excessive tamp pressure


  1. In your cafe you use the WBC scoring system to maintain quality. You’ve pulled five shots scoring only 3s in each category of the WBC scoresheet and the coffee has been tasting light bodied and sour the whole time with shots falling between 20 and 30 seconds.

Should you?

a.) accept the scoring ceiling has been reached for this coffee and remove this coffee from service.  

b.) fine the grind and explore shot times between 30-40 seconds

c.) increase the water temperature.

d.) b and c.


  1. You’re pulling shots that all taste sour and you are on a 40second shot time and a fine grind. You are on a 50% ebf and yet they still taste sour. There is not bitterness or astringency in the cup and you know the coffee is a good coffee from a reputable roaster and makes a lovely filter.

What will most immediately reduce sourness?

a.) increase water temperature

b.) drop the dose and pull the shot longer

c.) grind finer still

d.) increase pre-infusion


  1. Preinfusion helps increase extraction because

a.) it allows you to grind finer

b.) it reduces fines in the cup

c.) it increases overall brewing temperature

d.) it increases flow rate


  1. Your are getting excessive channelling.

Would this be most likely be cause by?

a.) your tamper being slightly convex

b.) the way you insert the portafilter into the group

c.) flow restrictors being too small

d.) overdosing the filter basket


  1. You are pulling big split triples at 24-55g. You detect over-extraction.

Would it be most efficient to?

a.) drop the dose and grind finer

b.) increase the dose

c.) decrease the beverage size

d.) coarsen the grind


  1. You detect over-extraction in a brew

Would the most likely reason for this be?

a.) one of the ingredients in your blend is lower density

b.) one of the ingredients in the blend is castillo variety

c.) the water you are brewing with has dropped in TDS to 50ppm

d.) your roaster has just employed a new head roaster


  1. You are scoring what you think is a 3.5 out of 6 on the WBC sensory score sheet but you sense there’s a 4 there just around the corner.

Should you?

a.) just serve it

b.) ask the customer if they’d like you to serve this one or if they want to wait a second while you tighten up the grind

c.) nutate a little more

d.) remove quakers from the hopper and winnow out the chaff from the centre cut


  1. Your company has established a scoring minimum of 3.5 in all categories on the WBC sensory score sheet and they expect you to hit this target in 4 shots. You have pulled 4 shots during dialling in and none of them have hit the 3.5 you’re after.

Do you?

a.) kept pulling shots on different recipes until you hit the god shot shot you always knew was there

b.) just serve it

c.) take the head barista aside and suggest the current blend might be hitting a ceiling below your quality threshold so they better contact the roastery to negotiate a better coffee for the next order

d.) send this coffee back and ask for a refund


  1. Your coffee tastes a tiny bit roastier than the previous batch from last week.

Do you?

a.) pull the shots longer

b.) pull the shots a touch shorter and reduce extraction and increase brew strength

c.) increase the dose and grind finer

d.) decrease the dose and grind finer


  1. The best coffee equipment is that which

a.) achieves the highest extraction on a given shot time

b.) slows down the rate of extraction

c.) has the lowest astringency ceiling

d.) is the most temperature stable


14.The best grinder burrs are those that

a.) reduce fines production

b.) reduce boulders

c.) increase sweetness

d.) have a higher astringency ceiling


The best grinder is

a.) the easiest to clean

b.) the most ergonomic

c.) that which maintains a stable shot time and dose

d.) all of the above


  1. The best barista

a.) does the dishes and smiles at the customers

b.) tastes the most

c.) needs to make the fewest changes to the grinder

d.) makes the most changes to the grinder


  1. The best dosing and tamping technique achieves the

a.) lowest extraction over a given shot time

b.) achieves the highest extraction over a given shot time

c.) achieves the lowest flow rates at the highest pump pressure

d.) distributes the coffee the fastest.


  1. The best roasted coffee

a.) gives the broadest extraction and shot time range for balanced shots

b.) tastes the most full bodied

c.) extracts the most easily

d.) tastes the most balanced


  1. The best espresso machine

a.) dispenses the most stable water temperature

b.) is the easiest to service

c.) is low profile so you can see the customers; is ergonomic and looks fantastic

d.) is under counter


  1. An espresso is balanced when

a.) it has no bitterness

b.) there is an harmonious balance of sweetness, acidity and/or bitterness

c.) it is the sweetest

d.) when it is 18-22% extraction


  1. The best tamper

a.) has a ripple base

b.) allows for the best pre-infusion

c.) reduces channelling

d.) promotes the highest extraction yield


  1. You grinder burrs probably need replacing

a.) every 250kg

b.) when the grinder starts heating up above 45degrees during busy periods

c.) when you taste flavours associated with over extraction when your average extraction yield is under extracted

d.) when the grinder takes more than 3.5 seconds to produce 18g of grinds


  1. You coffee tastes sour. Is your water likely to be?a.) too high in calciumb.) too high in KHc.) too low in sodiumd.) too low in KH
  2. Brewing at 11 bars of pressure will?


a.) increase flow rates

b.) permit me to grind coarser

c.) reduce espresso beverage size

d.) Increase channelling


  1. Hotter grinds during busy periods will?

    a.) decrease extraction

    b.) increase extraction

    c.) increase aromatic intensity

    d.) increase astringency


  2. The best distribution of coffee grinds is

a.) the method that promotes the fastest flow rate

b.) the method that moves coffee equally into the north, south, east and west of the basket

c.) the weiss distribution technique

d.) the method that promotes the highest extraction yield