Kaffelogic Roast Levels in Degrees: What the Number Means

"Run it at 2.2" is how Kaffelogic owners share roasts. It sounds like a universal setting, a bit like an oven temperature. It is not: a Kaffelogic roast level is a position on a temperature ladder, and every profile brings its own ladder.

We read that ladder in all 122 profile files we hold, including 105 of the 106 profiles in our roast profile library, and checked it against our own logged roasts on a Nano 7e.

The short answer: level 2 ends the roast at anywhere from 209 °C to 229 °C depending on the profile, and a 0.1 step can be worth 0.1 °C or 0.7 °C.

How a level becomes a temperature

Each .kpro profile file has a line called roast_levels with seven temperatures. They are the end-of-roast temperatures for levels 0, 1, 2, 3, 4, 5 and 6. Pick a level in between and the roaster interpolates. A higher level is a higher end temperature, so higher is darker.

We confirmed the mapping against 51 logged roasts. Reading the ladder as levels 0 to 6 predicted the actual end temperature to within 1 °C on average, with roasts finishing about 0.8 °C above the ladder value.

The ladders

All temperatures are in °C. Three different designs are visible here.

F-Series: even steps of 2 °C. Seven of the eight F-Series profiles climb exactly 2 °C per level (F-NAT 1000-1700 has a single 1 °C step between levels 2 and 3), and all eight recommend level 2. What changes between the altitude and process variants is where the ladder starts: level 2 is 210.8 °C on the lowest and 220 °C on the highest.

NCT: one big step, then very fine ones. On 20 of the 24 NCT profiles the jump from level 0 to level 1 is 4 °C or more, and through the middle of the ladder each level is worth only 1.1 °C. That 1.1 °C spacing between levels 2 and 3 appears in 22 of the 24. The whole usable range of a pack is packed into a few degrees.

The wide ladder: 36 °C from end to end. 9minFilter and twelve profiles in the library share the ladder 205, 215, 222, 227, 231, 235, 241. A single level is worth 4 to 10 °C, so it covers everything from a very light roast to a very dark one.

Across the library, the narrowest ladder spans 6.6 °C from level 0 to level 6 and the widest spans 36.5 °C.

The same setting on seven profiles

Here is what "2.2" asks for on each of the profiles above:

That is a spread of almost 11 °C for one number. Our logs agree with the ladders: roasts at level 2.0 on F-WSH 1500-2200 ended at a median 213.1 °C (the ladder says 212), level 2.2 on NCT Filter E ended at 221.4 and 222.0 °C (ladder 222.1), and level 1.7 on 9minFilter ended at 220.0 and 220.1 °C (ladder 219.9).

What a 0.1 step is worth

The standard advice is to adjust in steps of 0.1 to 0.2. How big a change that is depends on the ladder:

A 0.2 step on 9minFilter near level 1.8 moves the end temperature as much as 0.7 of a level on an F-Series profile, or more than a full level on an NCT filter pack. If a small adjustment on one profile seemed to do nothing and the same adjustment on another overshot, this is the likely reason.

It also explains why the recommended levels in the library look so inconsistent. They run from 0.1 to 5.9, with a median of 2.5, and the end temperature at the recommended level runs from about 205 °C to 240 °C.

You cannot convert a level by matching temperatures

It is tempting to read two ladders and translate: F-WSH 1500-2200 at level 3 ends at 214 °C, NordicLight reaches 214 °C at level 2, so they must be equivalent. They are not the same roast. The two profiles arrive at 214 °C along different curves and after different times, and the bean has been through a different roast by then. In our logs NordicLight finished in a median 5:55 and F-WSH 1500-2200 in 7:28.

End temperature tells you how far along a profile's own curve the roast stopped. It is comparable between two roasts on the same profile. It is a rough guide at best between profiles, for the same reason development time ratio is: see development time ratio on a Kaffelogic.

How to use this

• Quote the profile with the level. "2.2" means nothing alone. "NCT Filter E at 2.2" is a recipe.
• Start at the profile's recommended level when you switch profiles. Do not carry your usual number across.
• Size your steps to the ladder. On F-Series and NCT packs, 0.2 is a gentle nudge. On the wide ladder, 0.1 is already a real change.
• Watch the bottom of NCT ladders. On most packs the step below level 1 is about five times bigger than the steps above it.
• Compare end temperatures only within one profile.

Related Reading

• Kaffelogic Nano 7 profiles: library and download guide — the profile families and where to get them
• NCT vs F-Series compared by the numbers — how the two families differ beyond their ladders
• Development time ratio on a Kaffelogic — the other number that does not travel between profiles