Roaster: Gene Café CBR-301
Batch: 250 g
Set Temp: 250°C
Preheat: None
Fan: 2 → 3 at 4:27
Cooling initiated: 12:51 (771 s)
Output: 210.1 g
Weight Loss: 16.0%
Development (from crack flag): 83 s
Intent:
Repeat Roast 20 and align structural outcome to Roast 19 (~14.3% WL).
Why This Roast Exists
Roast 19 (Honduras Catuai Washed) landed at 14.3% weight loss and felt structurally balanced.
Roasts 18 and 20 (Guatemala Caturra Washed blend) both landed at ~16.1% weight loss.
Roast 21 was intended to bring the Guatemala coffee down into the same structural band as Roast 19 to allow a fair comparison.
Roast Behaviour
The roast behaved almost identically to Roasts 18 and 20.
- Drying progressed normally.
- Chaff began exiting in the expected 5–7 minute window.
- First crack was flagged at 11:28.
- Development time from flag to cool was 83 seconds.
- Cooling initiated at 12:51.
No instability.
No unexpected airflow behaviour.
No thermal crash.
From a machine standpoint, this was stable and repeatable.
What Actually Happened
Despite the intention to reduce weight loss, the roast landed at:
16.0% WL
This places Roast 21 structurally in the same band as:
- Roast 16
- Roast 18
- Roast 20
This is now a repeat-confirmed outcome for this coffee under this method.
The system is consistent.
Why It Did Not Align With Roast 19
The assumption going into Roast 21 was:
If development seconds are held similar (~80 s), reducing total roast time slightly would reduce weight loss.
What this roast suggests instead:
For this Guatemala Caturra blend at 250 g / 250°C / fan 2→3, the machine + coffee combination naturally settles around 16% WL when development is ~80 seconds.
Roast 19 was a different coffee (Honduras Catuai Washed).
Even with similar development timing, it reached 14.3%.
The difference is not only development seconds.
It is:
- Pre-crack energy accumulation
- Moisture content and density
- How this specific coffee converts applied energy into mass loss
This is a coffee response difference, not machine instability.
Structural Interpretation
At 16% WL, this roast sits in your established “fuller medium” band.
Expected structural traits (pre-cupping):
- Increased body
- Slightly reduced brightness
- More caramelised sweetness
- Slight compression of clarity compared to 14–15% band
This aligns with previous roasts of the same coffee.
What This Confirms
- The CBR-301 is thermally repeatable under identical settings.
- This Guatemala Caturra blend consistently lands at ~16% WL under ~80 s development.
- Development time alone is not the primary driver of structural band.
- Total applied energy and bean response matter more than crack timing alone.
This roast was not a misfire.
It was confirmation.
What Changes Next
If the goal is to move this coffee into the 14.5% band, one of the following must change:
- Reduce development to ~60–70 seconds
- Initiate cooling ~25–35 seconds earlier
- Or adjust total applied energy pre-crack
Simply “aiming lower” while holding development at ~80 seconds appears insufficient.
That is now an evidence-based observation.
Current Status
Roast 21 reinforces that:
The 16% band is stable for this coffee under current parameters.
The 14.3% band of Roast 19 belongs to a different coffee response pattern.
The dataset is beginning to show coffee-specific structural signatures.
No conclusions about preference yet.
Cupping will determine whether this 16% band is actually optimal for this coffee.