The machines / Amravati
Notes from the workshop
One machine roasts every bag. The next one, we're building. Every batch is logged in Artisan; every design decision starts with a question worth asking.
01 / What roasts your coffee
A 1.2-kilogram electric drum roaster that heats with carbon-fibre infrared and hot air. The drum answers quickly when we ask for a change, and heat reaches the bean bed without relying on hot metal alone.
Small batches are the whole point: 1.2 kg is enough to feed the shelf, and small enough that no bag comes from an averaged, anonymous roast.
It runs tethered to Artisan, the open-source roasting software. Bean temperature, environment temperature and rate of rise are recorded live on every batch. Those logs are measurements; the interactive curve in our lab is a separate, illustrative model built from fixed anchors.
Understand the roast curve02 / From green to roasted
What happens between the charge and your cup. These are the stages we watch, not a single batch's measured timeline; timings and temperatures vary with the roast.
1.2 kg of green Melghat robusta into a preheated drum. The probe reads the drum's stored heat, then plunges as the cold beans drink it in.
Around 90 seconds, the fall stops — the beans have caught up, and the climb begins. Where this lands tells us if the charge temperature was honest.
Moisture leaves the bean. Grass-green becomes pale gold. Rushing this phase is the most common way to ruin a good lot, so we don't.
From ~143 °C, sugars and amino acids start building the hundreds of compounds you'll eventually smell. We hold a falling, never-crashing rate of rise through this window.
Near 196 °C, steam pressure fractures the bean audibly. The development clock starts — every profile we publish states its time and temperature.
Sipna Serenade drops at ~18 % development for sweetness; Melghat Midnight runs to ~24 % and beyond for its dark, smoky spine. The drop call is the roast.
Down to ambient in under three minutes, rested to let CO₂ settle, then packed. Robusta likes a few days of rest before it opens up — your bag states the roast date.
03 / A machine of our own
In fabrication / Not roasting production batches
A one-kilogram convective drum machine, designed in Amravati from patents, primary-source roaster literature and first principles.
We benchmarked it, number by number, against the Aillio Bullet R1, Diedrich IR-1, Yoshan DY-1, Giesen W1A, Probat P05 and San Franciscan SF-1. Where the industry publishes no number, we say so.
Build specifications / Design figures, not validated performance
In a conventional solid drum, much of the roast air bypasses the tumbling bean mass — it takes the path of least resistance over the top. Rob Hoos documents it; every solid-drum roaster fights it. Our drum wall is 32.7 % open, so air is pulled radially through the bean bed itself. None of the six reference machines we benchmarked do this.
Roast exhaust and bean cooling never share ducting. A merged path back-pressures the drum the moment a finished batch hits the cooling tray — Scott Rao calls it a classic consistency killer. Separate blowers, separate runs.
The drum moved from 1.5 mm austenitic 304 to 2.0 mm ferritic 441 — not for heat, for physics. 304 deforms permanently at a 26 K thermal gradient; ferritic tolerates 65 K. The extra half-millimetre steadies the turning point batch after batch.
Batch size changes where airflow stops adding heat and starts stripping it — Aillio's own data shows that crossover moving from fan step 5 at 400 g to step 9 at 1.2 kg. You can't tune what you can't vary, so drum speed and airflow are continuously variable.
The honesty ledger
The perforated wall only beats air bypass if the exhaust hood pulls evenly through the bean bed. That needs a smoke test on the built machine, and we'll publish the result either way.
Our roast-exhaust blower reads oversized against every reference machine, so the damper's low end has to deliver genuinely gentle airflow for drying. When we know, you will.
The point of all this? A better cup.
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