250 g batches | 250°C set | 4 consecutive roasts
Objective
To test:
- How the Gene Café CBR-301 behaves across multiple back-to-back 250 g roasts.
- Whether cooling to 60°C fully resets the machine.
- How start temperature affects:
- Time to 200°C
- Time to 230°C
- Total roast time (TRT)
- Final weight loss %
This was a system experiment, not a flavour experiment.
All roasts were Brazil Santos Natural, 250 g input, target temperature 250°C.
Cooling cycles were allowed to complete to 60°C between batches in line with manufacturer expectations.
Measured Data Summary
| Roast | Start Temp | 200°C | 230°C | Cool Time | Weight Out | WL % |
|---|---|---|---|---|---|---|
| 28 | ~21°C (cold start) | 4:10 | 7:09 | 13:10 | 210.5 g | 15.8% |
| 29 | ~61°C | 3:00 | 6:00 | ~12:xx | 210.9 g | 15.6% |
| 30 | ~63°C | 3:02 | 6:04 | 12:45 | 208.1 g | 16.8% |
| 31 | ~63°C | 3:07 | 6:10 | 12:30 | 209.8 g | 16.1% |
Ambient room temperature: ~20–21°C.
Core Observations
1. Cooling to 60°C Does Not Reset the Machine
Despite running full cooling cycles:
- Roast 28 (true cold start) reached 200°C at 4:10.
- Roasts 29–31 reached 200°C around 3:00.
That is a ~60–70 second acceleration.
Conclusion:
The Gene Café retains significant internal heat mass even after cooling to 60°C.
The machine is operationally safe at 60°C — but thermally not equivalent to ambient.
This is a behavioural characteristic, not a flaw.
2. Early Phase Compression Is Real
Hot-start roasts showed:
- Faster climb to 200°C.
- Faster climb to 230°C.
- Earlier fan shift behaviour.
- More aggressive early energy delivery.
This compresses:
- Drying phase
- Early Maillard entry
Without changing the programmed set temperature.
Conclusion:
Machine thermal state materially alters roast curve shape even when inputs are identical.
3. Total Roast Time Becomes Less Predictable Under Heat Saturation
Cold start:
- 13:10 → 15.8% WL
Hot machine:
- 12:45 → 16.8%
- 12:30 → 16.1%
Shorter time.
Higher weight loss.
This confirms:
TRT alone is not a stable proxy for roast level when machine start temperature varies.
Weight loss remains the primary validation metric.
4. Santos Responds Cleanly to Energy Front-Loading
Across the 15.6%–16.8% range:
- No oil spots.
- No visible scorching.
- No erratic behaviour.
- No clear instability.
The bean appears structurally tolerant in the 15–16.5% band.
This is useful for both personal preference mapping and “friend roast” targeting.
5. Dynamic TRT Guardrail Established
From this session:
Cold Start (Ambient Machine)
If:
- 200°C ~4:00–4:15
Then: - ~13:00–13:10 = 15.8–16%
Hot Machine
If:
- 200°C ~3:00–3:10
Then: - 12:30–12:45 = ~16–16.8%
This becomes an operational rule:
Adjust TRT based on 200°C milestone timing.
If 200°C arrives early, you must shorten total time accordingly.
This is now a working field guardrail.
Structural Mapping Context
Within the broader Santos arc:
- ~15.0–15.5% → Acid-forward, thin, slightly green perception.
- ~16.0% → Target comfort zone candidate.
- ~17% → Upper boundary risk region.
This session intentionally populated the 15.6–16.8% band.
That gives a proper structural ladder:
15.6 → 15.8 → 16.1 → 16.8
Clean. Sequential. Measured.
System Lessons (Project-Level)
- The Gene Café has thermal memory beyond visible cooling.
- Ambient + machine start temperature must be considered in any predictive model.
- TRT cannot be universal; it must be contextual.
- Weight loss remains the most reliable roast-level anchor.
- Sequential roasting is predictable — but not identical.
- Front-loaded energy increases effective development even when final time is shorter.
- Manufacturer cooling guidance can be followed while still producing valid experimental data.
What This Session Was
This was not:
- Random roasting.
- Chasing darker colour.
- Trying to “fix” flavour.
This was:
A controlled heat-saturation experiment to understand system behaviour under sequential load.
And it worked.
Open Questions (For Tasting Phase)
- Does 16.1% represent the structural sweet spot?
- Is 16.8% fatiguing or simply rounder?
- Does body increase without introducing dryness?
- Does milk integration improve meaningfully above 16%?
Those are sensory questions.
This session answered the mechanical ones.
Final Conclusion
The most important takeaway is not which roast tastes best.
It is this:
The machine is predictable — but only when you account for its thermal state.