the finger sez: deidrichize your roaster!

September 12, 2007 – 10:58 pm

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roasting log: written proof this blog has no idea what it’s doing.

let’s ignore the incoming new york times traffic, shall we? and insist that this is still some hack blog

they laughed when CI vowed to “simulate the beneficial aspects of the cold” weather on hot-air coffee roasting. well nigh two years later, we might be getting close! handicapped as we are with roasting machines that huff and puff in small batches, it was nate the finger‘s idea to deidrich-ize these babies, stealing a page from the drum-roasting juggernaut by controlling the airflow in the roast chamber — instead of temperature itself — to help sculpt an ideal, curvy roast progression.

longtime blog sufferers will recall that numerous attempts to lengthen the amount of time it takes to bring a third-pound of green coffee to a palatable finish have been jettisoned, in part because hot air is so efficient, and can nicely do the cooking in much less time that it takes a rotating drum and a stationery heat source.

imagine the scoffage, then, when the finger told us he was executing 10-minute air roasts. this blog’s exact taunt, it seems, was something along the lines of, “you think you’re a finger, nate, but really you’re just a pinky with a mood ring.” or something to that effect. we can remember our 10-minute roasts producing totally, er, unheard-of coffee flavors. like, say, newt tail.

but here’s the key: we had tried to slow down a roast only by lowering the programmed temperature. nate has altered only the speed at which heat exits the roast chamber. he also takes rather seriously the advice to warm up the granules slooooowly. to do this, this blog has begun using the lowest temperature setting on the roaster and leaving the lid off for four minutes. then, with a fairly standard temperature escalation (400 degrees for three minutes, 455 for four minutes), we’ll ease into first crack — with the lid still off. watching the actual chamber temperature carefully (as opposed to what is programmed), we’ll wait until the temp stalls, not escalating for 10 straight seconds. then we slam on the “first” lid, or the chaff collector (lid diagram).

this has the effect of nudging up the temperature in the chamber by trapping more heat, and since the i-roast has two layers to the top lid, you get to do it twice! only the second time, this blog waits until after the first crack has died, the pause has stretched to 30 seconds or so, and the temperature again threatens to flatline. throw on the second lid, and the batch skips into second crack, which is somewhere near our usual finish line, but the arrival a lot slower and easier to replicate.

in other words, the finger has found a way to program a general roast curve, then tweak it on the fly by restricting airflow whenever a batch needs “help.” it’s like a ghetto, hot-fan roastmaster trick — without the industry jealousy and secrecy! unfortunately, this requires actual personal attention and precludes leaving a roast in progress and, say, completing a private wax. but the results are startling and somewhat mystical. will that deter this blog from far-reaching, overswift and faux-conclusive homilies? it will not.

homily the first: there’s chaff all over the laundry room. that’s what those lids were for!

homily the second: these beans don’t taste chalky, brick-like or overbaked like previous long air roasts. we have no idea why.

homily the third: using the lids — or playing with airflow — allows a home roaster to more deftly manage the length of time between first and second crack. as the rule of thumb goes, the shorter the pause, the higher and brighter the acidic citrus notes in the finished cup. the longer the pause, the more caramel and chocolate shows up. presumably, you could even find hot tar.

homily the fourth: the longer profile, and the freewheeling use of airflow restrictions, seem to greatly negate the profound influence of ambient temperature. previously, a roast curve was only good as long as the weather stayed the same. changes in room temperature and humidity have caused this blog to lose all interest in formerly exalted coffees. lid-juggling is a great way to compensate.

homily the fifth: nate the finger is a studly boar-pig.