Roast 103: Swiss Water Decaf on the Gene Café CBR-301

REDBER SWP Decaf Personal

Gene Café CBR-301 | Restored-heater phase | Personality 3

This roast was the first decaf I have roasted on the restored-heater version of my Gene Café CBR-301.

By this point, the machine had already shown a clear pattern after the correct replacement heater was installed. The Brazil cold-start roasts suggested the machine was behaving consistently again. The warm Guatemala roasts showed that it could carry a lot of momentum when warm.

So for this roast, I wanted to be careful.

Decaf can be awkward. It can look darker earlier than regular coffee. It can behave differently in the cup. It may not give the same clear sensory cues. And because this was the first Swiss Water Process decaf on the current machine state, I did not want to push it too far just to prove a point.

The question was simple:

What does this decaf do on the restored-heater machine from a cold start?

Not what is the perfect decaf roast.
Not what is the final profile.
Just the first safe reference point.

Roast details

Field	Value
Roast number	103
Coffee	REDBER SWP Decaf Personal
Process	Swiss Water Process decaf
Roaster	Gene Café CBR-301
Machine phase	Restored heater / “Personality 3”
Input weight	250 g
Output weight	217.2 g
Weight loss	13.1%
Start temperature	22°C
Target temperature	250°C
Cooling started / roast ended	11:30
First crack	Not confidently recorded
Fan 2 → 3	4:56 / 221°C
Fan recovery 3 → 2	10:39 / 247°C

The roast file recorded 250 g in, 217.2 g out, and 13.1% weight loss. The roast started cold at 22°C and ended at 11:30.

Weight loss calculation

The app-reported weight loss checks out:

250.0 g - 217.2 g = 32.8 g loss
32.8 / 250.0 = 13.12%

Rounded, that is:

13.1% weight loss

For this first decaf roast, that puts it in a cautious, low-to-moderate development area rather than a pushed roast.

That was intentional.

Expectations before the roast

Before starting, my thinking was cautious.

The setup was:

250 g
250°C target
Cold start
Swiss Water Process decaf

My initial working target was:

Cool around 11:45

With an acceptable first-test range of roughly:

11:30–12:00

The reason for that range was not because I knew this decaf needed 11:45. I did not.

It was because this was the first decaf roast on the restored-heater machine, and I wanted to avoid carrying over timing assumptions from regular coffees.

The Brazil cold-start anchor had gone much longer, around 13 minutes, but decaf is not Brazil Yellow Bourbon Natural. It deserved its own first reference.

My expectation was:

if the roast looked normal and the milestones were sensible, aim near 11:45
if it ran fast, pull earlier
if it looked unusually slow or pale, consider stretching toward 12:00
do not casually drift beyond 12:00 on a first decaf test

The main idea was:

Safe first anchor first. Optimisation later.

Real-time checkpoints

During the roast, I watched the milestones closely.

The live readings came in as:

200°C at about 3:41–3:42
230°C at about 5:37–5:38
Fan / overheat intervention at about 4:56–4:57

The final JSON shows:

Milestone	Time
200°C	3:42
230°C	5:37
240°C	6:27
245°C	6:56
249°C	7:21
250°C	7:28

The JSON also shows the fan moved from 2 to 3 at 4:56, when the displayed temperature was 221°C.

That told me this roast was not slow.

The 200°C time was in the expected area, but the 230°C time was quick, and the fan intervention before 5 minutes showed the machine was carrying decent energy.

That changed the decision.

The live decision

The original expectation was around 11:45.

But once the roast hit:

200°C at 3:42
230°C at 5:37
fan 3 at 4:56

the roast no longer looked like something I wanted to carry to 11:45 without question.

So the decision became:

Pull earlier. Do not let the first decaf test drift too far.

The live target moved to:

11:25–11:30

The final roast ended at:

11:30

That was not a random change. It was based on the roast’s actual pace.

This is exactly the kind of decision I want to make more often with the Gene Café. Not chasing the graph. Not pretending I have precise profile control. Just using the app and the milestones as comparison signals.

What actually happened

The roast reached the upper temperature band fairly quickly.

It hit 245°C at 6:56, 249°C at 7:21, and 250°C at 7:28. From there, the machine cycled around the top band until cooling was started at 11:30.

The fan returned from 3 to 2 at 10:39, around 247°C, then the roast was stopped less than a minute later.

The final result was:

217.2 g out from 250 g in
13.1% weight loss

That is lower than I might have expected from a roast that moved through the milestones quickly.

But it makes sense.

The machine had energy, but the endpoint was deliberately conservative.

Observed

The machine was energetic from cold

This was a cold start at 22°C, but it did not feel sluggish.

Compared with the recent Brazil cold anchor, Roast 103 reached key milestones slightly faster.

Milestone	Roast 100 Brazil cold	Roast 103 SWP decaf cold
Start temp	22°C	22°C
200°C	3:47	3:42
230°C	5:49	5:37
245°C	7:17	6:56
250°C	7:49	7:28
Fan 2 → 3	5:39 / 228°C	4:56 / 221°C
End time	13:13	11:30
Weight loss	15.3%	13.1%

The decaf reached 200°C, 230°C, 245°C, and 250°C faster than the Brazil cold-start roast.

That is worth noting.

But the final weight loss was much lower because the roast was stopped much earlier.

The early fan intervention mattered

The fan moving to 3 at 4:56 / 221°C was a useful signal.

I do not want to overinterpret that as a precise internal diagnosis. I do not know exactly what the machine is doing internally.

But as a practical user signal, it told me the roast was moving with enough energy that I should be cautious.

That is especially true with decaf, where colour and surface appearance can be misleading.

First crack was not a control point

There was no useful first-crack marker in this roast record.

That is not a problem.

For this roast, first crack was not the main control point. The decision was based on:

cold start temperature
time to 200°C
time to 230°C
fan intervention
visual caution
total roast time
the fact that this was a first decaf anchor

That fits the broader learning from the project.

First crack is useful when it is clear. But on this machine, and especially with some coffees, it cannot be the only stopping signal.

Interpretation

My current interpretation is:

Roast 103 was a safe first decaf anchor on the restored-heater machine.

It was not necessarily the final target for this coffee.

It was not designed to be.

It was designed to answer a simpler question:

Can I roast this SWP decaf safely from cold on the current machine state without overshooting?

The answer appears to be yes.

The roast moved quickly enough to confirm that the restored-heater machine still has strong cold-start energy, but the 11:30 endpoint kept the weight loss down at 13.1%.

That is useful.

Expectation versus reality

Expectation

Before the roast, I expected that a Swiss Water decaf might need caution and that the safe first endpoint would likely be somewhere around 11:30–12:00.

My initial leaning was around 11:45.

Reality

The roast reached 200°C at 3:42 and 230°C at 5:37. Fan intervention happened at 4:56.

That made the roast look faster than I wanted for a casual 11:45 finish.

So I pulled at 11:30.

The result was 13.1% weight loss.

What changed

The roast’s pace changed the plan.

That is the most important part of this note.

I did not stick to the initial target just because it was written down. I also did not make a dramatic mid-roast intervention. I simply used the early checkpoints to decide that the safer endpoint was the earlier end of the planned range.

That feels like progress.

Expected cup direction

I have not yet treated this roast as judged by taste. The cup result still matters most.

Based on the roast record alone, I would expect one of two possible outcomes.

If it works well

It may present as:

gentle
soft
low bitterness
easy-drinking
possibly useful with milk
not especially heavy
a safe evening coffee style

If it is underdeveloped or too light

The signs may be:

thin body
short finish
flat sweetness
papery or cereal-like edge
decaf “hollowness”
not much structure in milk

That would not surprise me at 13.1% weight loss.

It would simply mean the first anchor was safe but a bit too conservative.

If it tastes roast-heavy

That would also be useful, though less expected from the weight loss.

If the cup is dry, ashy, or harsh, then the endpoint was not the only issue, and the decaf itself may need a different approach.

But my current expectation is that the more likely risk is too gentle or slightly thin, not over-roasted.

What I would do next

The next step depends entirely on the cup.

If Roast 103 tastes balanced

I would keep the next roast close to:

11:30

That would make this a good first decaf baseline.

If it tastes light, thin, or hollow

I would extend the next roast.

My next test would likely be:

250 g
250°C
Cold start
Cool around 11:50–12:00

A practical target would be:

11:55

That would test whether a little more time improves body and finish without pushing the decaf too far.

If it already tastes roast-heavy

I would stay near 11:20–11:30 and look more closely at brew method, rest time, and how decaf colour is affecting judgement.

Practical lesson

This roast reinforced one of the strongest lessons from the restored-heater phase:

The machine can move quickly, but the endpoint still matters enormously.

Roast 103 was not slow. It reached the upper temperature bands quickly and triggered fan 3 before 5 minutes.

But because cooling started at 11:30, it finished at only 13.1% weight loss.

That is useful because it prevents a lazy conclusion like:

“The new heater just makes everything roast darker.”

That is not what this roast shows.

A better conclusion is:

The restored-heater machine builds momentum quickly, so the endpoint has to be chosen carefully.

That is a much more useful way to think about it.

Current verdict

Roast 103 is a successful first decaf calibration roast.

Not because I know it will be the best-tasting decaf.

I do not know that yet.

It is successful because it gave me a safe reference point.

I now know that on this machine, with this coffee, from a 22°C cold start, a 250°C target and an 11:30 endpoint produced: