Airflow - Settings and Use

All of our roasters come equipped with variable airflow. Manually controlled roasters include a dial on the control panel with markings of 0-100 that represents a wide spread of airflow from potentially way too low to potentially way too high. As part of learning to control your machine, it is helpful to establish and use 3 settings:

• Low
• Medium
• High

Don’t get hung up on the dial numbers. Different roaster and batch sizes and venting schemes make precise fan settings impossible to share. Instead, grab a cigarette lighter and watch the way the flame pulls into the tryer port to get an idea of how much airflow your fan is pulling at various settings. 

1. Pull out the trier from the trier chute.
2. Put the lighter withing 1/4" from the bottom of the chute port. When the flame bends into the chute at about a 45 degree angle, this is low. Note your dial setting.
3. Next, find medium fan airflow. Light the flame and when the flame bends heavily into the chute, this is medium. Note your dial setting.
4. Finally, find high fan airflow. Light the flame and when it lights but extinguishes, this is high. Note your dial setting. You probably won’t go above this setting unless your fan or venting is crudded up enough to affect airflow.

All of our roasters include a digital drum pressure gauge to verify airflow numbers. Once you establish optimal low, medium and high setting for various batch sizes, you'll have a drum pressure readout to verfiy that you are actually moving the ideal volume of air through the system for that particular batch size.

If the drum pressure reads low for any given setting, you'll probably need to bump the fan speed to get to your roast air back to "normal" and then plan on cleaning something soon.

Now that we have the settings, how is airflow used? This is how we use airflow when we roast.
1. Low. From “charge” to end of drying, use an airflow setting of low. This permits the roaster to bring the core temperature of the beans up to the same temperature as the outside portion of the beans. This also dries the bean and sets you up for a successful roast.
2. Medium. From end of drying to about 30 seconds before first crack. Anticipate 1st crack: look at the seam (begins to open) and examine the beans under the light. You will see the slightest smoke coming off the beans.
3. High. From 30 seconds before first crack to end of roast, open the airflow to high. Get that smoke out of the roaster. Don’t go above the setting for high that you have determined by the use of lighter. “More” is not better. Excess airflow can stall the roast and/or force you to use more burner heat. Both can have a negative effect on the flavor of the coffee.

It's your roaster and your coffee. You can do things anyway you want, but getting airflow dialed in a very good place to start.