How to use BT/IT and BT/Power profiles
These two profile types work in a different way to regular time-based profiles. This guide explains how — and when — to use them.
Note: This profile type works best with batches 120g and above, where the BT probe is most accurate. For roasting batches smaller than this, we recommend using standard inlet profiles or air temperature profiles.
How temperature-based profiles work
Standard roasting profiles are based on time. The profile tells the roaster: “When the roast reaches X seconds, then change the setting to X”.
Temperature based profiles (BT/IT and BT/Power) are based on the progression of bean temperature instead. The profile tells the roaster: “When the bean temperature reading reaches X, then change the setting to X”.
Because this is a completely different way of controlling the roast, temperature-based profiles have a few specific features:
Temperature-based profiles assume that after the turning point, the bean temperature is always increasing. If the bean temperature decreases, the profile will not run in reverse! Instead, the roaster will stay at the same point on the profile until the bean temperature increases again.
Until the turning point, the bean temperature is decreasing. Therefore the profile will stay on the first temperature or power setting until the turning point. At the turning point, the profile will jump ahead to the next step according to the current bean temperature.
The BT/IT profile stays on the first setting until the bean temperature reaches the turning point. At the turning point, the profile jumps to the next point on the profile curve.
- Since different beans heat up at different rates, the same profile will have different roast times with different coffees. If your beans heat up more quickly, the profile will run more quickly.This means that you can’t control the roast time directly with this type of profile. If you want to make the profile run more slowly, for example, then you will need to reduce the heat input so that the beans heat up more slowly.
- The bean temperature increases more slowly towards the end of the roast. Changes near the end of the roast may need to be made only a few degrees apart.
Points on the profile towards the end of the roast are close together on the BT/IT profile, but far apart in time, because the bean temperature is increasing more slowly at this time.
Creating a profile
Create a new profile and select BT/IT or BT/Power as the profile type
On the next screen, you can create your profile in the normal way by adding points manually (A) or dragging them around on the graph (B)
The X-axis represents the bean temperature, instead of roast time
You can still choose to end the roast based on development time, total roast time, or bean temperature as normal (C)
Creating a BT/IT profile
The easiest way to get started with a BT/IT or BT/power profile is to base it on an existing roast curve. At present, this must be done manually.
Open the log that you want to use as a template.
Make a note of the starting inlet temperature (A)
Make a note of the bean temperature and inlet temperature (or power) at the turning point (B) by hovering your mouse over the curve and reading the values on the tooltip
Make a note of the bean temperature and inlet temperature at several points along the curve after the turning point, in particular anywhere where the curve changes shape (C)
Enter those values into a BT/IT profile to recreate the curve.
Roast a batch of coffee using this profile as a starting point, and make adjustments as needed.
Troubleshooting
Profile curve is not smooth at the beginning but suddenly jumps to a different setting
This is normal for this type of profile. The profile will hold at the starting setting until the turning point. At the turning point, the profile will jump to the next stage of the roast.
Profile doesn’t advance or beans stop heating up
The profile will not move to the next stage if the bean temperature does not increase. Use a higher inlet temperature or power setting to ensure the bean temperature is increasing throughout the roast
My roast looks different to another ROEST user’s when we share the same profile
Small differences between machines, installation, and the beans themselves affect the way beans respond to roasting. When sharing profiles with any profile type, but especially with BT/IT profiles, you will need to make small adjustments in order to get satisfactory results.
