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.
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.