iRoast Roast 4 (Viennese+ 14min 10sec.) May 2005
Roast4-AGraph1 |
Roast4-Thermocouple |
Roast4-ScreenChaff |
Roast4-CoffeeFinal |
This was an experimental roast, as you can see in the graph, the top lid was opened twice, in an attempt to slow down the 20dF/min. temp. ramp-up beginning at 9 minutes.
ROAST PROFILE
Stage 1: 325F, for 5 minutes
Stage 2: 390F, for 7.5 minutes
Stage 3: 440, for 2.5 minutes
Total Roast Time: 14minutes, 10 sec.
Comparing Roast 2 and Roast 4, both ran slower than the 125-127V roasts (Roast 1 & Roast 3).
It must be said, my iRoast is highly affected by its input voltage, or at least load voltage. I'm not an expert, but the results seem to speak to this fact.
Nonetheless, at minute 8, Roast 2 was at 408dF while Roast 4 is at 421dF, a 12dF difference. Explained by the higher ambient temperature (74dF vs. 81dF)? Or perhaps this batch had more chaff, or the machine isn't that consistent.
At minute 9, the fast ramp-up begins: I spontaneously decided to crack the lid briefly, to let some chaff escape and perhaps slightly decrease the ramp. It may have worked, however the thermocouple didn't register it right away--this is probably because it was surrounded by beans. You notice though that the iRoast readout reacted sharply, 30 sec. later. But I was watching my thermocouple, and decided to crack the lid a second time. This time, I was clumsy and couldn't get it snapped into place right off, so maybe 1-1.5sec. elapsed with it cracked. This combo of events saw a temperature dip, up until Stage 3 kicked in. Will the 5dF dip in bean bed temp., over about 90sec. have stalled the roast? I'll be cupping in a couple days to find out.
I suspect a chaff effect at 9 minutes. My goal was to do an extended 14minute roast, creating longer a profile, which brings the beans slowly up to second crack, so they heat evenly, develop flavor, and don't get stressed. From 2nd crack to the end of the roast, I'd like to move temp up more quickly (no problem with the iRoast doing this in Stage 3). Though I'm more interested in the Full City to Vienna range, I brought the above beans to a 470dF bed temperature, just beyond Roast 2 (466dF), partly to see how Stage 3 was working, and what would happen past 14 minutes.
The drying phase 80F-300F is better than Roast 3, but still short. Yet my heating stage 300F-390F was longer (worse) and end stage much too long..
Roast 5 will be a 150gram load. I notice that in Roast 1, the last part of the roast has a rather stately temperature ramp -- could this be partly due to greater bean-bed mass? The issue of chaff remains as well. If nothing else, I may try the lid technique again, perhaps refine it.
I'm interested in your suggestions and comments.
Richard G
comments welcome. email
gilbert(at)iyume(dot)com
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