Why this comparison exists
These two roasts were not about flavour discovery.
They were a controlled check:
Does the Gene Café CBR-301 behave like itself when the batch size is reduced to ~52g?
One roast started cold.
One roast started warm.
Both were set to 250°C.
This Note documents what actually happened.
Measured Data (Side by Side)
| Metric | Sample Roast 1 | Sample Roast 2 |
|---|---|---|
| Coffee | Costa Rica Geisha (Fermented & Washed) | Costa Rica Red Honey (San Isidro 48) |
| Batch | 52.5g → 45.1g | 52.5g → 44.3g |
| Weight Loss | 14.1% | 15.6% |
| Start Temp | 21°C (cold) | 52°C (warm) |
| Set Temp | 250°C | 250°C |
| Total Time (cooling initiated) | 11:10 | 11:47 |
| End Temp | 250°C | 244°C |
| Crack Flag | 10:20 | Not flagged |
| Dev (flag→cool) | 0:50 (~7.5%) | N/A |
| Fan 2→3 | 4:22 | 3:51 |
| Fan 3→2 | 7:50 | 7:28 |
All timings are taken from the roast logs. Cooling initiation defines total roast time.
Observation 1 — The Machine Still Behaves Like the Machine
Even at ~52g, the Gene Café:
- Increased fan speed automatically around the 4–5 minute region
- Later returned the fan from 3 back to 2
That behaviour is consistent with full 250g batches.
This is important.
It suggests that airflow/protection logic is driven by internal thermal conditions — not by bean mass alone.
Small batch does not turn this into a different machine.
Observation 2 — Warm Start Changes Early Pacing, Not the Whole Roast
The warm-start roast (52°C start):
- Reached milestone temperatures earlier
- Triggered the fan increase slightly earlier
- But still finished at 11:47 — not dramatically shorter
Once thermal equilibrium is reached, the roast curve settles back into the machine’s normal rhythm.
Warm starts influence the opening phase.
They do not override system behaviour.
For comparability, cold starts are cleaner.
Observation 3 — End Temperature Is Not a Roast Level Indicator
- Roast 1 ended at 250°C with 14.1% WL
- Roast 2 ended at 244°C with 15.6% WL
Despite the lower end temperature, Roast 2 lost more mass.
This reinforces a recurring project conclusion:
On the Gene Café, weight loss + total applied time are more reliable roast-level anchors than end temperature alone.
Especially when crack is ambiguous.
Observation 4 — Crack Audibility Remains Coffee-Dependent
- Geisha roast: crack audible and flagged
- Red Honey roast: pops heard, no clear crescendo, no flag
This does not indicate success or failure.
It reinforces something already observed in larger batches:
Crack audibility varies by coffee.
It is not a reliable sole stop cue.
Structural Conclusions (Within Scope)
From these two small roasts:
- The Gene Café expresses consistent airflow/protection behaviour even at ~52g.
- Warm starts accelerate early momentum but do not fundamentally change total roast behaviour.
- Weight loss remains a stable, batch-size-independent measurement.
- End temperature alone is not a development metric on this machine.
- Crack sound remains secondary to measured endpoints.
No flavour claims are made here.
This is purely about system behaviour.
Why This Matters
If the machine behaves predictably at 52g:
- Sample roasting becomes viable.
- Small-batch testing becomes meaningful.
- Consistency studies can scale down without losing integrity.
That’s the real takeaway.
Next Steps
- Brew and assess structurally (body, balance, finish).
- Keep sample roasts cold-started for cleaner comparability.
- Continue logging fan events explicitly in all Notes.
Because on this machine, airflow events are part of the profile.