Rate of Rise after Dry End

A friend asked what range of RoR I get after the first "Drying" phase of the roast. It's mostly between 10ºC/min and 4ºC/min, with a slight 'bulge' when the beans start to crack and heat escapes from the 'pressure cooker' hot cells that burst open. 

When that bulge happens (around 10mins here) the probe gets hotter but the expanding and bursting bean cells themselves do not get so much hotter. It's like lifting the spout off a hot kettle. You suddenly feel extra heat on your finger tips but that does not mean the kettle just suddenly got hotter.


Chris zei…
I liked your comment about the RoR bulge and what it actually is indicating... only a reference about the thermocouple's quick response to the relatively short steam release during 1st crack. The beans on the other hand never respond so fast. Until now, they've needed many minutes to get up to temperature, and are much slower at taking on heat at this point. I don't get overly concerned with it. I picture an imaginary connecting line from where the bulge starts to where it ends and stabilizes... to me, this shows the true RoR trend and how the environment actually affected the beans. :)
Frans zei…
Exactly! I agree with your 'imaginary connecting line' idea.

In the approach to the FC I gradually lower the heater energy & increase airflow. Some of the bean energy release is absorbed by the bean mass which compensates this.

Some who do not understand the FC energy 'puff' quickly lower energy as soon as they see the 'bulge' and next they are struggling to deal with the sudden crash of RoR after the 'steam exhale' moment has passed just as their lowering of energy or increase of cool air inflow is taking effect.

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