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Delta BT Flick

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nickthorpie:
Hey all,
As per Rao's recommendations, I am able to maintain a constantly decreasing delta BT, up until the seconds leading up to 1C. As you have all seen, the curve pretty much does everything you don't want it to; It drops heavily, and then increases just as quickly as it started.

After some quick reading, it appears that what appears on the screen might be a bit misleading.. The general consensus is that the steam escaping from the beans cools the probe, and when the steam dissipates, the temperature reading goes back up(flicks) to a more realistic level.

What do I do at that first crack time? Do I crank up the power, then shut it off to produce that smooth ROR, or do I just let the end of the roast just do its thing? Has anyone Cupped the difference? I feel like I'm doing everything right and then butchering it at 1C

folkery:
I wouldnt increase the heat to improve the flick. Scott Rao mentions not to do that. In his blog he talks about it often. Increasing the heat only produces more unwanted toasty flavors. He suggest finding a way to get an ever declining RoR by other means. I'm thinking he means airflow. Airflow can increase convective heat transfer to the beans. Just a little may fix the flick. Also try to anticipate the flick, maybe start more airflow just before FC begins.

folkery:
Also from you graph it does look like the flick starts before FC. What steps did you perform before that? I'm curious.

folkery:
I also have a hunch that your roast is progressing too fast as I can you have 5 kpa mid roast. Also from your BT line it is so steep it doesn't bend forward tapering off at the end of the roast.

Gregr:
Scott Rao doesn't use a Huky  :D  If he did then he would know that we can mitigate that big dip without imparting any roast notes at all. It is tricky though and takes a little practice but it absolutely can be done so stretching the final phase out a bit is possible if that is something you want to do. I suspect much of Rao's comments are aimed at roasters that don't have the agility of the Huky.
If you're a fan of the steadily declining bean temp delta ignore the rest of the roast and note that once first crack starts I raise the heat from 1kPa to 1.5 or so for about 30 seconds, then lower it back to 1.0 til first crack is over, then .5kPa for maybe 30 more seconds, then the heat goes off for the rest of the stretch, if any. The fan remains at 25% until first crack is done, then 75% until the heat goes off- then full fan. The numbers vary a little bit depending on what the beans are doing but the overall technique works very well for keeping enough momentum going without any roast notes appearing. That roast was for espresso, by the way, and the shots are very rich and creamy smooth.

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