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Roasting is just cooking — controlled, repeatable cooking. You take a dense, grassy, almost flavorless green seed and apply heat over time until it becomes the fragrant brown bean you grind. Your entire job as a roaster is two things: get heat into the bean at the right rate, and stop at the right moment.
What roasting actually is
Green coffee is a seed. It holds 10–12% water, a store of sugars, acids, proteins and lipids, and essentially none of the aroma we associate with coffee. Heat changes that in two broad stages: first the water boils off and the bean's structure stabilizes, then a cascade of browning reactions builds hundreds of new aromatic compounds while the bean turns brown, swells, and eventually cracks audibly.
Underneath all the jargon you'll meet, there are really only two levers, and they show up again and again: how much heat you apply (energy in) and how fast the bean's temperature rises (the rate). Apply heat too aggressively and the outside of the bean races ahead of the inside — scorched shell, raw core. Too gently and you "bake" it: flat, papery, lifeless. Good roasting lives in the middle, and most of this guide is about finding and controlling that middle.
You're cooking with heat — and heat travels three ways
Before any talk of machines, understand the physics, because it's the same in every roaster ever built. Heat reaches a coffee bean by three mechanisms:
- Conduction — heat by direct contact, like a bean resting against a hot metal drum wall. Powerful and immediate, but the contact point can scorch if it's too hot.
- Convection — heat carried by a moving fluid, here hot air or combustion gas flowing past the beans. Even, gentle, and easy to modulate by changing airflow. This is the workhorse of modern roasting.
- Radiation — infrared energy beamed from any glowing-hot surface (a burner, a drum wall) without touching the bean at all.
No roaster is purely one mode. What separates a drum roaster from your Nano is the mix — and that mix is the single biggest reason the same green coffee can taste different off two machines.
The family of roasters
You'll see all of these in the coffee world. The concepts in this guide apply to every row:
| Type | Heat mix | Control | Feel |
|---|---|---|---|
| Drum | Conduction + convection + radiation | Manual, real-time (gas + airflow knobs) | High thermal mass: momentum, forgiving, but slow to react. The commercial standard. |
| Fluid-bed / air ← your Nano |
Almost pure convection | Airflow + heat; on the Nano, an automated profile | Fast, even, very clean in the cup. Low thermal mass: responsive and a little less forgiving. |
| Hybrid | Drum with strong forced air | Manual, real-time | Tries to get drum body with air-roast clarity. |
| Air popper | Convection | Basically none | The $20 way people discover they love roasting. |
Phases, cracks, rate of rise, development — these mean the same thing on a $20,000 drum and on your benchtop Nano. So we learn the physics first, with generic numbers. When it's time to talk about actual knobs and quirks, that's Part IV: Roasting on the Nano.
Your Nano, in one sentence
The Kaffelogic Nano is a fluid-bed convection roaster (about 100 g a batch) that runs an automated profile: you design the temperature curve you want, and the machine's controller executes it. That's a genuinely different mental model from a manual drum, where you ride the heat by hand — and it's worth keeping in the back of your mind as you read. We'll come back to exactly what that means for you.
How this guide is built
The chapters stack deliberately:
- Foundations — the bean, and what heat does to it.
- Anatomy of a roast — the phases, the cracks, the rate of rise, and the drop. This is the heart of it.
- Flavor & roast level — where taste actually comes from, and the light-to-dark trade-offs.
- The Nano — mapping all of it onto your machine.
- The simulator — drive a virtual roast and watch every idea above come alive.
Next up: the raw material itself.