Airflow has two important functions in coffee roasting: it removes smoke and chaff from the drum, and it enables convective heat transfer. Scott’s recommended approach to managing airflow is very simple: choose a setting and stick to it.
Airflow changes make a roast profile much more complicated because changing the airflow will have different effects, depending on the gas setting. When the gas setting is high, increasing the airflow blows more heat into the roaster, boosting the bean temperature (BT) and exhaust temperature (ET) rates of rise. At very low gas settings, on the other hand, increasing the airflow may cool the roaster down and decrease the rates of rise. As a result, if the airflow has also changed,