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Unit 6 Dales Brewery, Gwydir St
Cambridge, England, CB1
United Kingdom

(01223)359966

Hot Numbers is a high quality, independent gourmet coffee-house and roastery in Gwydir St, Cambridge. Providing delicious hand roasted coffee, speciality tea and light bites, to include pastries baked on site plus home-made cakes and paninis. We even stock Fitzbillies famous chelsea buns & cakes!

A hub for interesting folk to meet and chat accompanied by great jazz and blues music. Call in and enjoy the wonderful space of Dales Brewery. A true find for any discerning coffee enthusiast.

 

Blog

Naked Portafilters and Issues Extracting.

Hot Numbers

 

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Words: S. Lynch

You might not have been able to find a seat. You might have queued for ten or fifteen minutes in hot-house conditions to be greeted by the fierce, perspiring faces of a team working in a degree of unison more common to multi-limbed gods of eastern religions. Or, Line Dancers. 

 Perhaps we didn’t look so cool and collected at times, but nobody seemed to mind the wait on Saturday. If there’s one thing you should definitely expect at a winter fair in a small English town (asides from dry mince pies and booze before midday,) is a lovely big queue.

 But we did our best to keep that queue moving. We had a production line system in place, one taking orders, one pulling shots, another steaming milk, and the last pouring the milk and making sure it gets to the right customer, all with a level of communication usually reserved to top level government security organizations. Or line dancing. (Jokes do get funnier if you repeat them.)

 

If you familiarised yourself with this a couple of weeks ago: "All things considered" then you’ll know I’m a fan of information overload and in depth processes. So after a slightly meandering start I thought I’d write this blog post on one of those processes - the espresso pull.

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Can’t be that hard right? We just “tip’ espresso into cups don't we? I’m not hot on my Italian verbs and tenses but I’m pretty sure ‘espresso’ is not something that can be tipped. (Also I have the upper body strength of an 11 year-old asthmatic and La Marzocco Lineas are heavy.)

Sarcastic anger may seem a bit unnecessary but there are a lot of variables we have to consider when getting the espresso right. There are some pretty in-depth books on the subject that get into laws of fluid dynamics and heat potential…and also refer to multiple baristas as ‘baristi’ (but that’s when I stopped reading.)

I dropped chemistry after GCSE so I wont attempt to go into such depth, and what I write is purely based on what I’ve experienced, and what I’ve tried reading before giving up. (Caffeine seems to weaken patience.)

So the main variables to our espresso coffee methodology:

GRIND
 TAMPING

EXTRACTION TIME
WATER PRESSURE
DOSE
& TEMPERATURE

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Grind:

Ask anybody who makes coffee; a bad grinder will not make a good coffee. It’s all about variation in coffee particle size and surface area. So forget about blade grinders for espresso, they chop the coffee fairly indiscriminately so you end up with dust and chunks. The tiny particles will extract a lot quicker than the larger chips meaning the resulting coffee will be a mix of both under extracted (sour lifeless coffee) from the big chips and over extracted (astringent bitter coffee) from the tiny bits. Those fines will also end up towards to bottom of the basket, and in large enough quantity can block the flow of water, enough disrupt that steady flow. Not ideal!

Burr grinders with sharp burrs do a pretty good job of grinding evenly. But then you have to get the coarseness correct, the high pressures involved in espresso mean you have to grind the coffee fine enough so it packs tightly into the portafilter with no air spaces.

-Too coarse and the air spaces will let the water blast through far too quickly, not giving it any chance to extract any flavour.

-Grind it too fine and the water is resisted so much it will stall in the basket. 

One notch difference on the grinder can flip the balance... espresso is the temperamental, highly strung friend of the mild mannered filter. 

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Tamping:

This is where you’re packing the perfectly ground coffee into the basket. This is a massive point of contention and experimentation in the world of "Baristi" -trawl Youtube for 'tamping techniques' and you’ll probably find more mustachioed men taking themselves seriously than a Victorian circus; explaining their rituals and craft which are likely 3 parts coffee science, 1 part repressed thespianism.

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It’s a delicate operation. Those grounds need to be evenly distributed throughout the basket because, as we all know from science, water follows the path of least resistance. If the packed grounds don’t provide the same amount of resistance throughout then you get the water pushing through the areas of less resistance, over extracting one part of the coffee and barely extracting the rest. All that hard work at the grinder un-done! Similarly, if you’re cack-handed or a bit hasty and push the coffee into slope you’ll get the same channeling. And a cup of bitter water.

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So a consistent tamping method becomes some sort of art, banging out espresso shots like Jackie Chan on the wooden dummy. Part Tai-Chi, part cookery.

Time,Pressure, dose and temperature:

The coffee machine needs to control all of these consistently, a machine with a double boiler and PID controller means less chance of dips in temperature, maintaining the espresso temperature to within half a degree. All of these factors still need to be kept in check. One coffee bean may call for a higher dose, more grounds to water than another. Too much H20 and not enough coffee compounds and you’ll have a wishy-washy, soul-less espresso shot with no body. And if you change the volume of grounds in the basket you’ll effect the extraction time, more coffee will slow the water down, so you’d then have to adjust the grinder again to bring it back into harmony. And you can time a shot, either manually with a stop watch and scales to measure how long it takes to dose a certain volume of water. Or you might fix the dose to a certain amount, then the machine gives you a read out of how long it takes for that volume of water to push through the coffee bed.

Common practice suggests 25-30 secs for a 30g of espresso, in that time range you're extracting a good balance of oils and aromatics. Shorter than that you risk under extracted sourness, longer than that you could be extracting too much acridity. But then each coffee is different. The first 15 secs of an espresso might be beautifully sweet with subtle sharpness for one bean. Or 36 secs might produce a smooth balanced shot for another, depending on their roast profiles and individual characters. 

(On a side note there's some been some buzz over the past months about the EK43 Grinder allowing much larger yields and longer "coffee shots" which taste fantastic apparently. More here and here. )

So let's say you've got the timing down, you know how each bean reacts and you've found a good time range (for that bean on that day- not taking into account how it's flavour may alter as it develops in the time after roasting. Or if you're palate is more sensitive one day than another.)  

But it still might fall into the desirable 25-35 sec range and still be channeling and extracted unevenly, which is why having open bottoms or “naked portafilters” is so helpful. And pretty. You can see the coffee spiral from the machine and gradually change from rich reddish black to caramel blonde.  You can see if the water is pushing through and over extracting one side of the puck. If you get it really wrong you’ll get wet as the high pressured water sprays out through a channel.

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Sometimes it feels like being a kid with a chemistry set. A big, shiny boiling hot, metal machine of a chemistry experiment.  

Add all of this up with steaming milk (worthy of it’s own preachy blog post,) milk pouring, making sure the music isn’t too loud and the tables are clean and clear and the double dipped spoon that’s hardening in the sugar bowl on table 4 is dealt with… production line systems are necessary on Winter Fair days when you make 560 espresso based drinks in the space of 10 hours that all need to be of a consistent quality.

So don’t take it personally if you get dirty looks when you ask for “the toffee thing like what Costa do.” It’s not personal. It’s just when you spend 12 hours a day pretending to be Walter White and Jackie Chan you tend develop a slightly narrow view of the world.

Hopefully. You might not have been completely bored by the blog post. You might even have had your curiosity piqued, if so we offer much more in depth, less sarcastic, hands-on Barista training here at Hot Numbers. Check out the packages here: hotnumberscoffee.co.uk/baristatraining, for yourself or for that coffee fanatic you have no idea what to buy for Christmas..

If you fancy reading a more eloquent and much more accurate and knowledgeable blog about the coffee world then you could do worse than James Hoffman's blog: www.jimseven.com

But make sure you come back here next week. Cheers!