How Should I Use the Roasting Air and Drum Speed Controls?

Here are some best practices for your early roasts on your San Franciscan Roaster.

Note: The instructions listed below are suggestions for new roasters who have purchased an SF-10, SF-25, or SF-75. They are by no means the only method for roasting effectively and are not meant to represent a required mode of operation for the roaster. The operator of the roaster should always ensure airflow components are clear and free of chaff and other debris prior to roasting. 
  • When first becoming familiar with the operation of the roaster, set your roasting air to 100% (i.e. turned fully clockwise) and your drum speed to 50%.
  • Utilize only the mechanical air damper in the crossover pipe to control airflow during roasting.
  • With these settings, you will become familiar with the thermal behavior of the roaster, and you will see how the adjustment of the mechanical air damper impacts both the ambient air temperature (green temperature on the Watlow controller) and the bean temperature (red).
  • During roasting, it is important to ensure there is a negative pressure in your roaster's drum. This ensures that chaff, smoke, and ash are pulled off of the beans and into the chaff cyclone, and also improves the taste of the coffee that you are roasting.
  • To verify the pressure in your drum, temporarily remove the bean trier from the face plate during roasting. If there is chaff coming out of the trier well, there is a positive pressure in the drum. Replace the bean trier and open the mechanical air damper incrementally to return negative pressure to the roaster's drum.
  • After performing enough roasts to begin correlating the roaster's settings with the various flavors developed during the roast, you can begin adjusting the roasting air and drum speed controls. These control the ratio of convective and conductive heat transfer that the beans experience during roasting. However, it is not advised to turn the roasting air down to below 50% with the mechanical air damper closed at any point, as this will cause the flames to be "lazy" and will not remove chaff, smoke, and ash from the drum effectively.