We began our roasting journey on a Probat P05 III, a machine that has challenged us, taught us, and fundamentally reshaped the way we think about roasting coffee. Learning to roast on this roaster pushed us to question assumptions we once took for granted and encouraged us to approach every decision with greater intention and precision.

One of the very first things we focused on was understanding and defining the correct roast volume and drum RPM. On a traditional drum roaster, coffee beans are repeatedly lifted and dropped through the roasting drum, where they are fully exposed to hot air during their falling motion. This moment is crucial, as it is when convective heat transfer is most effective.

To make optimal use of this convective heating, the number of beans in free fall at any given moment needs to be carefully balanced. Too few beans, and heat application becomes inefficient and inconsistent; too many, and airflow and heat penetration are compromised. For that reason, our initial experiments centered almost entirely on determining how many kilograms we should roast per batch and how fast the drum should rotate to create the most even and efficient movement of the beans.

By dialing in these fundamentals, we created a solid and repeatable foundation. From there, we believe that all further adjustments—airflow, gas settings, and roast profiles—should be dictated by the coffee itself. Each coffee has its own structure, density, and potential, and our role as roasters is to respond to that rather than impose a fixed approach.

This roaster has already opened the door to countless learning moments, and we are incredibly excited about the many roasting adventures that still lie ahead. Every batch is another opportunity to refine our craft and deepen our understanding of coffee.