Refining the roast

Since I’ve last written here I’ve moved house, changed jobs and had a few adventures, all fuelled by a certain healthy addiction. On that front, I’ve done a lot more roasting, although less than I would have liked to (all of the above can have that effect), and I’ve also finally gotten around to buying an Aeropress and falling in love with it as a way to make coffee at work. I still haven’t got one for home and I occasionally shuttle it back for the weekend, but I like to get the V60 or the Cona out when I’ve got a bit more time to brew.

On to roasting – I’ve settled on a fairly simple roast formula that I know I can follow consistently and achieve good results with most coffees on the Quest, and with that as an anchor I’m experimenting to learn how different coffees respond to various roasting inputs (temperature, airflow, time). I’m using my home-grown Excel-based roast monitoring system which is about as bare bones as it gets but gives me all of the information I need at this point, sampling the two thermocouples I’ve got connected to the roaster (in the drum and bean mass) and plotting the temperatures on a live graph. On top of that I record roast time, charge weight and roasted weight and I can work out a lot of other information from there. I had some issues with Artisan and my temperature sensor but it’s been a while, I ought to get around to either trying Artisan again or fixing the issue. Let’s make that a 2016 goal.

I’ve also been reading Scott Rao‘s excellent and concise Coffee Roaster’s Companion, which is a great resource for anyone looking to get into roasting – it’s pitched at a great level for beginner to intermediate roasters and I feel that even seasoned roasters would be able to get some  meaningful insights from Scott’s years of experience, experimentation and research.  There is a lot of debate around his conclusions online, but in any case it’s helpful to have someone present their theory and justifications for it to spark debate and experimentation.


My simple roast formula at the moment looks a bit like this:

  1. Preheat the roaster to about 220 degrees Celsius and allow the temperature to stabilise – usually about 10 mins or so from cold
  2. Reduce the power to about 4 amps (low-medium power) and charge the coffee
  3. Watch the bean mass temperature and allow to stabilise – when it starts to level off, raise the power level
  4. Watch the coffee closely, as the beans start to yellow start raising the fan speed and tapering the power to slow the rate of rise in the drum temperature
  5. By the time first crack starts, the fan should be on full and the power somewhere around the 4-5 (medium power) mark – when first crack is in full swing, the power should be on the lower end of that range as the beans will carry themselves exothermically through the crack
  6. Aim to dump at around end of first crack just before the start of second, depending on the coffee

I’ve been able to get great results with very few roast defects with the above formula in the back of my mind, and a fairly close eye on the graphs to make sure the temperature doesn’t stall or shoot up too quickly with different beans (i.e. too much power on naturals or relatively low water content beans, and vice versa). I’d love to know what other people’s mileage has been with the Quest to see how their experience has varied over time after getting a good number of roasts under their belt.

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(A Tribe Called) Quest

It’s been a while since I’ve written about roasting (or anything).  I’m glad to say this is more a factor of busyness than anything else; I’ve been roasting pretty much constantly since I found the replacement for my old Whirley-pop.

My new chosen roaster to dip my toes into more controlled and scientific roasting is the Quest M3 – a drum-style electric roaster with an ideal batch size of around 120g (though I frequently roast closer to the maximum 200g):

The Quest M3 roaster

The manufacturer in Taiwan makes them to order, and with a few customisable options (like the dual thermometers shown above, or K-type thermocouples).

I got this just before Christmas and I’ve averaged around 2.5 roasts a week since then –  the results have been fantastic.  I’ve been able to record my roasts extremely accurately using a pair of thermocouple probes in place of the thermometers shown above and some VBA jerry-rigging to get the roast results directly into Excel – very work in progress, haven’t even implemented smoothing out the error samples seen below for one:

Roast curve


And here’s a picture of the roasting setup with the thermocouples:

Roasting setup

With my set-up pretty much nailed for now, my next challenge is going to be to roast as often as possible, be methodical with storing and recording my results and develop my cupping skills to start being able to make some objective judgements about the kind of coffee I’m brewing, and compare it to some of my favourite roasters’ coffee (hello Square Mile, Workshop, Nude…)

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Brewing with the Cona

A friend was kind enough to lend me his Cona coffee maker, and I fell in love with it so much that I ordered one of my own.


This coffee maker works on the vacuum principle.  Water heated in the lower chamber turns into steam, and the increased pressure forces it up a column topped with a glass counterweight into the upper chamber, where it cools enough to condense back into water.  At this stage you add the coffee.  If we continue to apply heat this creates a balanced system where the vapour pressure is high enough to keep the water in the top chamber and at a very constant temperature, until the heat is removed.  At that point, atmospheric pressure and gravity overcome the now diminished force of the water vapour from below, and the water, now hopefully infused with coffee, falls back into the lower chamber, gently pulled down by the relative low pressure below (hence the ‘vacuum’ or ‘siphon’ method).  At this point the glass counterweight now serves an ingenious second purpose, helping to keep the grounds descending into the lower chamber.

The beauty of this method is in its consistency – the temperature of the water remains very constant, and in contrast with other methods like pourover there’s very little to the technique and out-gassing of very freshly roasted coffee is less of a problem, so you can count on great results every time.  The coffee that comes out is very clean-tasting.


My preferred method is as follows (for the Size C 900ml model):

  1. Boil 1L water in a filtered water kettle (or use filtered water in an ordinary kettle).
  2. A little while before the water finishes boiling, light the spirit burner and place it under the bottom chamber of the Cona.
  3. Pour boiling water into the bottom chamber, filling it about 90% of the way.
  4. Very gently place the step of the top chamber with the glass counterweight inserted into the neck of the bottom chamber and give it a half-turn to create an air-tight seal.  Do not press down or force the top chamber.
  5. Weigh out about 50-60g of coffee, medium ground.  This should give a water to coffee ratio of roughly 16:1.  Avoid fine ‘espresso-ground’ coffee.
  6. Once the water has finished rising into the top chamber, the little glass counterweight should start rattling gently against the glass in the top chamber (there should still be some water left at the bottom of the lower chamber).
  7. Set a 3-minute timer, pour the coffee into the top chamber and use a flat spatula-like object (like a regular table knife) to gently stir the coffee in a circular motion, making sure to avoid the centre of the top chamber (don’t knock the glass counterweight!)
  8. After the first and second minute, give the coffee a stir to break the crust and keep some turbulence in the water.  Take care not to overstir or you risk over-extracting the coffee.
  9. When the 3-minute timer is up, pull the heat away and watch the magic happen.  The coffee will be drawn down into the lower chamber.
  10. Once the pressure equalises, gently remove the top section by twisting it another half-turn and lifting, and rest it on the special slot built into the stand.
  11. Let the coffee in the bottom chamber cool for a couple of minutes – this method results in the coffee being very hot straight after brewing, and it’ll need a few minutes to cool down before it’s at an optimum drinking temperature.

For more info, take a look at:

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I’m looking for a new roasting method!  I’ve been learning a lot and getting some great results from the stovetop roaster but it’s finally given up the ghost:


I’ve been sticking to 250g roasts each time, and unfortunately the tiny plastic gears just couldn’t handle the strain.  I guess green coffee is a fair bit heavier than popping corn, and I’m using quite a lot of it each time!

I’ve some ideas for alternatives, and I think it may be time to graduate to a more fit for purpose device.  I’ll share some news as soon as I’ve decided exactly what that might be.

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Coffee 101

I’m a big fan of Has Bean – they have a great selection and they’re really convenient if you’re looking to source green coffee.  They also have a treasure trove of information on their website about all aspects of coffee: growing, processing, roasting, brewing, etc.

In addition to resources available on their main site, Steven Leighton from Has Bean has assembled a free ‘Coffee 101’ course at  When you sign up you receive ten e-mails over ten days, in which he guides you through the history of coffee, through to brewing tips, covering a number of interesting topics along the way.  Each mail is a 5-minutes read, but covers a lot of good introductory content to spur the reader’s interest.

I took away a few pointers, specifically around water – I spotted that Richard Williams over at Nude Espresso also just wrote a blog post on this.  Water quality is all too easily overlooked and quite an easy thing to improve.  At the very least it’s worth knowing whether you live in a hard or soft water area, and bearing this in mind when you’re making your next brew.

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