Turning 6


Turning 6

Crankhouse turned 6 this week.

6 years ago this was my first attempt at roasting on the Petroncini that I’d bought second hand (or 3rd or 4th) from James at SHP. 7.5Kg of a honey processed Costa Rican community coffee from the Tarrazu region.

The English language manual James promised never arrived and instead I had three sheets in Polish which when translated described the basic operational procedure of the machine and what each switch and warning lamp on the control panel meant.

I’d given it a good clean and tidy up and removed the blackened charred remains of kilos of poorly treated coffee beans from behind the side panels and even took the burner out to take a look at the state of the burner head.. although to be honest I had no idea what I was looking at/for.

The first main challenge was getting it up and running in my garage since it required a three phase electrical connection (again I had no idea what that actually meant although the big red round 5-pin plug made me think I couldn’t just stick it in the 3-pin on the wall). I hired a rather overpowered 3-phase diesel generator and a friend towed it on the back of his truck and plonked it in front of my garage. Fired it up and bingo, the main power button in the control panel sparked to life. Then what to do. Tuned the drum on.. OK, the exhaust fan on.. OK then the cooling fan and the mixer. Odd that something looked wrong to my very untrained eye. The mixer blades looked like they might be mounted wrong and wouldn’t actually mix/stir very effectively. Hhhmm. 3-phase motors can run in either direction depending on the order the 3-phases are wired. Something else to stick in the ’things I’ve learnt today’ book.

I’d been on the 3-day ‘how to start a coffee roastery’ course at the London School of Coffee run by Morten Munchow which covered some of the basic theory of heat transfer and we’d used the lab 1Kg Diedrich machines a few times, manually mixing coffee in the cooling tray, and also 3 roasts on the Probat LP12 at Alchemy Coffee in Wimbledon as a group. One weighing the greens, one opening the gate to charge the drum, one on the keyboard recording first crack, one using the trier looking at colour change, one calling out the temp at 30 secs intervals, another filling in a manual roast profile record. As well as the 100’s of roasts on my dimmer switch modified Gene Cafe electric 300g ‘home’ roaster that was about the limit of my roasting experience. In real terms I was a complete novice.

At that point the Petroncini had a single-stage (ON/OFF) burner. ON was full-power, and OFF none. No ability to adjust the power and a very crude baffle/damper in the exhaust pipe to vary the air flow. I learned over time that I could use the baffle to crudely adjust the heat input and then at some point nearing first crack, turn the power off and allow the thermal inertia of the system to ‘guide’ the batch through.. in a fingers crossed, let’s hope for the best since I have no other option sort of way. I then worked out I could adjust the gas supply safety valve (designed to be on or off and not for control at all), to reduce the amount of gas entering the burner and as long as I didn’t turn it too far in the direction of OFF I could have some rudimentary non-repeatable control of the heat input. That combined with the damper and the burner ON/OFF switch made roasting  a bit like a dance in the dark. Ah, those were the days NOT !

I really couldn’t tell you what that Costa Rican coffee tasted like. I assume by looking at the curve with the knowledge and experience I’ve gained over the last 6 years that it would have been flat and heavy and probably quite roasty. No mouth-watering vibrant acidity, no yummy sweetness. Just heavy, dull and roasty. I didn’t possess the knowledge necessary to get the best from my roaster, nor the knowledge to know what the ‘best’ meant in terms of flavour (Lee Safar’s excellent podcast series ‘MapItForward’ recently highlighted the low barrier to entry required to start a coffee roasting business).

I’ve just done a quick check and give or take I’ve roasted 7650 batches on the Petroncini. At an average of 5Kg, that's just under 40 metric tonnes of coffee. These days it has a fully modulating burner with an excellent turn down ratio (ie it has a great range from low to high), as well as a VFD drive to control the air flow through the roaster in a repeatable way, high speed 2mm thermocouples reading BT and ET (virtual bean temp, and exhaust temp), and most recently digital differential pressure reading in the exhaust which gives data on the back pressure holding the exhaust gases back due mainly to the atmospheric pressure at the top of the exhaust stack. It’s not the machine it started out as, which I’m very thankful for.

I have a moisture meter, a UV lamp to identify mould and bacterial growth on green coffee and am just about to purchase a water activity meter to measure the water vapour pressure in greens. All useful data.

I’ve roasted on a number of modern small machines in the last couple of years at shows and retreats and coffee friends letting me use their machines: Giesen, Joper, Probat, Loring, Diedrich and Stronghold. All very shiny and new in comparison to my Petroncini. None ‘better’, none would make me a better roaster and none that I’d swap the Petroncinci for. Not that a new bigger capacity roaster isn’t on the wish list. Imagine that, all that modern functionality out of the box. So easy.

Today I roasted an anaerobic honey processed Pacamara from Federico Pacas in El Salvador. It’s the 5th time I’ve roasted this new coffee and it’s proving a challenge. Pacamara beans are large and porous with very low density. Combined with a relatively low altitude, high moisture content, anaerobic fermentation in tanks then slow shade drying make this one of the more challenging coffees I’ve roasted. 6 years ago I wouldn’t have stood a chance. I wouldn’t have had the control needed on the roaster, nor the knowledge to know that this isn’t your usual coffee. Like many things in life, coffee roasting doesn’t get any easier the more you do it. You just get more exacting and more focused on achieving the best result you possibly can. One day perhaps I’ll achieve the perfect roast…. one day...perhaps.

This week I listened to a fantastic Webinar hosted by Caravela Coffee with one of the superstars of specialty coffee Christopher Feran giving his thoughts on green coffee and aging/fading. WOW. This guy. WOW. Incredible knowledge. I understood some of the content, not all of it by far and it made me feel like there was still so much to learn, and that's just in processing, harvesting and storage.

Let's give it another 6 years and see what happens.

I can't imagine anyone has made it to the end of this post. If you have and you're up for trying our latest coffees (including the Anaerobic Honey Pacamara) then you can get a 6-pack of 150g each for £36 with delivery included (UK mainland only).

Just go to the link here to order your 6-pack.


Thanks for all your incredible support over the last 6 years. You know who you are.






1 Comment

  • Holly Kragiopoulos on

    Hi Dave! Hols here from North Star – just wanted to say I made it to the end of your blog :) Just interested in how you are going so great to read your updates after 6 years, wow! Hope you are well! x

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