[Coffee Roasting] Roaster Flame and Airflow Control (Part 2) | Coffee Workshop

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The need to adjust a roaster's heat and damper settings arises not only during the roast itself but also during the machine's initial preheating phase and in maintaining consistency from batch to batch. Each of these situations calls for adjusting heat and damper settings to get the result you want.

Preheating and First Batch Strategy

In FrontStreet Coffee's daily roasting, I use a semi-direct heat roaster. During the preheating phase, I set the damper to the middle position and the heat to 75%, a medium-high setting. This brings the roaster's temperature up quickly to the first batch's drop-in temperature. Once the roaster reaches the drop-in temperature, I let it climb to about 10 degrees above the drop-in temperature, then hold it there with controlled heat for about 10 minutes. After that I completely close both the damper and the heat, letting the temperature fall back to the drop-in temperature, then return the damper to the middle position and hold the drop-in temperature for about 5 minutes before dropping the first batch of beans.

The reason for this is that the temperature probe reads only one point, not the temperature throughout the drum. If you simply preheat to the nominal drop-in temperature and hold it for a while, the thermal energy stored in the drum is likely to be lower than the reading suggests. As a rule, I do not roast low-fault-tolerance beans first. Instead I start with medium-dark beans that tolerate more variation. Usually, after two batches, the roaster's condition stabilizes and I move on to roasting normal beans.

Post-Roasting Management

After each batch, and especially after a dark roast or a batch dropped at a high temperature, it is best to close both the damper and the heat completely and let the roaster's energy come down. At this point you may notice that the temperature does not simply fall because the heat is off; on the contrary, it can actually rise by several degrees. Once the temperature has dropped by about 5 degrees, set the damper to the middle position and raise the heat to bring the roaster up to the drop-in temperature, then hold it for about 1 minute before dropping the next batch.

There is no need to push the roaster above the drop-in temperature at this stage, because after roasting a batch the roaster already holds enough heat, and it is distributed more evenly.

FrontStreet Coffee Recommendation

Flame and airflow control is ultimately in service of a target: a roast level that suits the bean in front of you. Many of the most rewarding coffees sit in the middle of the range, where acidity, sweetness and bitterness are held in balance, and medium roasting is often where that balance is easiest to reach. FrontStreet Coffee's Brazil Queen Estate is a good example. Grown in Mogiana, near South Minas, on fertile red volcanic soil that feeds the cherries, it is planted with the rare yellow Bourbon, a natural mutation of red Bourbon whose fruit comes through cleaner. Roasted medium, it shows creamy peanut, chocolate, toasted bread and sugarcane, with a clean, gently sweet body, and it is flexible enough for pour-over, a moka pot or an espresso machine.

The Strawberry Candy Geisha blend is another medium-roast option, and a more unusual one. It combines two well-known Central and South American origins, a honey-processed Costa Rican coffee and a washed Panamanian Geisha, roasted medium so the cup carries both the Panamanian orange-blossom honey character and a round sweetness, and it suits cold brew, pour-over and espresso alike. For a lighter, more restrained expression, FrontStreet Coffee's 2013 Yunnan Sun-Dried Typica offers the classic small-bean Yunnan profile, roasted medium to preserve its balanced, gentle character with nutty, brown sugar, black tea and dried apricot notes, and it works in a pour-over, a cold brew or a drip machine. And for the benchmark of the style, the Jamaica Blue Mountain No.1 is roasted medium precisely because that level fuses its acidity, bitterness, sweetness and body into the elegant, immediately recognizable balance of chocolate, roasted nuts, cream and caramel that no other bean quite matches. Whatever curve you build, the point of the heat and airflow adjustments described above is to land consistently on the profile each of these beans deserves.