What we know before we start
The moisture and density readings from the lot, plus the origin, the processing method and the elevation. Together those tell us roughly what kind of coffee we are dealing with: hard or soft, how much water we need to drive off, and how much heat it will take without scorching.
That gives us a starting profile. It does not give us the right one.
The first roast is a question, not an answer
We roast a small batch, we cup it, and the cup tells us what to change. Too sour and grassy means we stopped too early. Flat and roasty means we went too far. Hollow in the middle usually means the heat came in wrong somewhere rather than at the end. Then we adjust and go again.
What we are actually adjusting
Charge temperature, which is how hot the drum is when the beans go in. Gas, which is how much heat we are putting in and when. Airflow, which moves heat around and carries off the chaff and the moisture. And time, especially the stretch after first crack.
Why a profile gets revisited
Because the coffee changes underneath us. A lot that has been in storage for months has lost moisture, and the profile that worked in month one will not be right in month eight. So profiles are not set and forgotten, they get checked against the cup.
Try this
Nothing to try at home for this one. But if you are ever in one of our cafes and the roaster is running, ask. It is the part of this job people most enjoy explaining.