Roast Machine Types
Sources: The Coffee Roaster’s Companion by Scott Rao (2014); Aillio (website); Kaffelogic (website); Nucleus Coffee Tools (website); Behmor (website); Home Roasting Supplies (website); Giesen (website)
A roasting machine is a specialized oven that transfers heat to coffee beans in a stream of hot gas while continually mixing them for even roasting. The design of the machine determines the proportions of convection, conduction, and radiation in heat transfer — which in turn affects the style of roasting and the range of profiles possible. (source: The Coffee Roaster’s Companion by Scott Rao (2014))
Heat Transfer Mechanisms
Convection: Heat transferred by movement of hot gas through and around the beans. Dominant in most specialty roasters.
Conduction: Heat transferred by direct contact — beans touching the hot drum wall or neighboring beans. Significant in classic drum roasters, especially early in a batch.
Radiation: Heat emitted from hot surfaces. Minor contributor in most machines.
Classic Drum Roaster
A solid, rotating cylindrical steel or iron drum laid horizontally, with an open flame below. Heat transfer approximately 70% convection, 30% conduction (per Probat estimates).
The drum acts as a heat-storage device: it stores heat energy that jump-starts bean development early in a batch when cold beans drop the air temperature. This is why classic drum charge temperatures are lower than other machine types — the drum compensates.
Double drum (two concentric layers with a gap): reduces direct conductive overheating of the inner drum surface; limits tipping, scorching, and facing risk. Recommended over single drums.
Single drum with heat shield: the shield becomes extremely hot (~950°F / 510°C measured with infrared thermometer) and radiates heat even when the flame is off, reducing the operator’s control.
| Classic Drum | |
|---|---|
| Heat transfer | 70% convection, 30% conduction |
| Charge temp range | 380–440°F (193–227°C) |
| Roast time range | 10:00–16:00 min |
| Advantage | Clean roasting environment; drum as heat reservoir |
| Risk | Overheating drum → bean-surface burning |
(source: The Coffee Roaster’s Companion by Scott Rao (2014))
Indirectly Heated Drum
Hot air from a combustion chamber is passed through the drum; the drum is not in direct contact with the flame. Drum stays cooler, allowing higher roasting air temperatures with lower burn risk.
| Indirectly Heated Drum | |
|---|---|
| Heat transfer | Higher convection proportion than classic drum |
| Charge temp range | 450–525°F (232–274°C) |
| Roast time range | 9:00–15:00 min |
| Advantage | Faster roasting at higher temps; lower bean-surface burning risk |
| Risk | Slightly less fuel efficient |
(source: The Coffee Roaster’s Companion by Scott Rao (2014))
Fluid-Bed Roaster
No drum. Beans are kept aloft and rotating in a high-velocity stream of hot gas. Heat transfer almost exclusively by convection.
Requires very high airflow early (dense green beans) and declining airflow as roasting progresses (lighter roasted beans). Many units lack a separate cooling bin — cooling in the roasting chamber is slower because surfaces remain hot. Buying a separate cooling bin is advisable.
| Fluid-Bed | |
|---|---|
| Heat transfer | Almost 100% convection |
| Charge temp range | Well over 550°F (288°C) |
| Roast time range | 7:00–11:00 min |
| Advantage | Affordable, reliable, small footprint, low bean-surface burning risk |
| Risk | Excessive airflow damages flavor; operator must compromise between ideal flavor settings and settings required for proper bean rotation |
(source: The Coffee Roaster’s Companion by Scott Rao (2014))
Recirculation Roaster (e.g., Loring Smart Roaster)
Returns a portion of exhaust air through the burner chamber to recapture heat. More fuel efficient than single-pass machines. The stable, moist, repeatable roasting environment improves compatibility with automated profiling software.
| Recirculation | |
|---|---|
| Heat transfer | Almost exclusively convection |
| Advantage | Fuel efficient; fast roasting; lower bean-surface burning risk; consistent environment |
| Risk | Beans dwell in smokier air; risk of smoky flavors in the cup |
Rao recommends single-pass roasters over recirculation roasters despite the energy efficiency, citing the smoky flavor risk. (source: The Coffee Roaster’s Companion by Scott Rao (2014))
Machine Selection Criteria
Configuration (most important)
Rao’s recommendation: single-pass + indirectly heated drum (or double drum). This combination maximizes flavor quality and minimizes bean-surface burning risk.
Capacity
- Manufacturer stated capacity is usually the maximum, not the optimum
- Most machines produce best results at 50–70% of stated capacity
- Rule of thumb for single-pass drum roasters: 1 lb per 5,000 BTU of rated output (1 kg per 11,606 kJ)
- Real-world single-pass efficiency is 50–75%; recirculation roasters are more efficient
Airflow
- Should be steplessly adjustable (not just 2–3 settings)
- Large airflow jumps create undesirable shifts in convective heat transfer and disturb the ROR
- Dedicated cooling fan preferred over shared roast/cooling fan
Gas Control
- Steplessly adjustable gas settings essential for profile precision across varying batch sizes
- Limited gas control on small machines is a cost-cutting choice by manufacturers, not a technical requirement
Cooling
- Full batches should cool to near room temperature in 4 minutes or less
- Rapid cooling prevents baked flavors and preserves sweetness
- Test cooling efficiency before purchasing
Drum Speed (RPM)
Suggested starting points for 60–80% capacity batches:
| Roaster capacity | RPM range |
|---|---|
| 5–12 kg | 52–54 RPM |
| 15–22 kg | 50–52 RPM |
| 30–45 kg | 48–50 RPM |
Consider gradually increasing RPM as beans expand during a roast.
Data Logging and Automation
- At minimum: digital bean-temperature probe, digital environmental probe, manometer
- Data-logging software (e.g., Cropster): tracks and displays ROR in real time — indispensable for applying the Three Commandments
- Automated profiling software: can control the roaster but current off-the-shelf systems often overreact to deviations and may compromise cup quality; useful for warm-up/between-batch/cool-down automation
Pollution Control
- Coffee roasting emissions include VOCs, aldehydes, nitrogen and sulfur compounds, carbon monoxide — many carcinogenic
- Afterburner (thermal or catalytic oxidizer) is the most reliable solution
- Thermal oxidizer: ~1400°F (760°C); very effective but consumes ~twice the fuel of the roaster
- Catalytic oxidizer: lower temp, less fuel, but requires periodic catalyst replacement
- Wet scrubbers and electrostatic precipitators: less reliable per Rao’s experience
Compact Specialty Roasters (1 kg and Below)
The machines described above are production-scale commercial roasters. A distinct category of smaller machines is used by home roasters, specialty micro-roasteries, and as sample roasters for profile development. These operate on the same physical principles but are designed for batch sizes of 50 g to 1 kg. (source: Roast Rebels (website))
Aillio Bullet (R1 / R2 / R2 Pro)
Compact induction-heated drum roaster. Key distinction from gas-fired drums: induction heating allows very fine, fast power adjustments with 9–14 discrete stages and ±0.5% power delivery precision (R2/R2 Pro). Also features an IBTS (Infrared Bean Temperature Sensor) that reads bean surface temperature directly (rather than air temperature), giving earlier and more precise signals than a standard thermocouple probe. Software (RoasTime + Roast.World) enables full data logging, profile replay, and community sharing. See Aillio for full profile. (source: Aillio (website))
| Bullet R1 | Bullet R2 | Bullet R2 Pro | |
|---|---|---|---|
| Capacity | 1 kg | 1 kg | 1.2 kg |
| Power | 1,550W | 1,700W | 2,300W |
| Stages | 9 | 10 | 14 |
| Price (USD) | $3,599 | $4,099 | $5,299 |
| Price (ex. VAT, EUR) | €3,017 | €3,529 | €4,453 |
EUR prices from Roast Rebels; USD prices from Aillio direct. The R2 and R2 Pro add a barometric pressure sensor (altitude compensation) and FlowSense (airflow monitoring).
Kaffelogic Nano 7
Fluid-bed (fluidized air) roaster from New Zealand. Roasts 120g standard; 50–200g in 10g increments with the BOOST Kit (1,087 USD direct. Compact (3.6 kg, 125mm footprint) — suitable for kitchen, lab bench, or origin facility. Kaffelogic Studio software (free, Mac/Win/Linux) provides bean + fan curve control, live roast view, and pre-loaded profiles (cupping, washed/natural, espresso, and more). Used as a sample roaster in specialty roasteries and quality control at origin. See Kaffelogic for full profile. (source: Kaffelogic (website))
ROEST (Norway)
Convection sample and production roaster manufacturer. New Generation sample roasters (S200, L200 Plus, L200 Ultra) support up to 200 g with touchscreen interface and OTA firmware. The L200 Ultra adds Counterflow mode — drum reverses to drive beans directly into the airflow, enabling either ultra-fast roasting (100 g to 2nd crack in 90 seconds) or low-temperature roasting (inlet <230°C) that eliminates surface defects and reduces energy 20–30%. The P3000 production roaster (1–3 kg; up to 25 kg/hour; SCA Best New Product 2025) bridges into production at micro-roastery scale. All machines connect via the free ROEST Connect software platform. See ROEST and Sample Roasters. (source: ROEST (website))
IKAWA (London)
Hot-air convection sample roaster manufacturer (est. 2010; sold to 74+ countries). Four models — GO (50 g, one-button), Pro50/Pro100 (50/100 g, app-controlled), Pro50x/Pro100x (50/100 g, adds humidity sensor, Auto-Detect First Crack, and Target Development Mode). The Roastmaster (5–20 kg, joint product with Bühler) is a full production drum roaster positioned as the natural scale-up from the IKAWA sample line. See IKAWA and Sample Roasters. (source: IKAWA (website))
Nucleus Coffee Tools LINK
Hot-air convection sample roaster (50–100 g) from Australian manufacturer Nucleus Coffee Tools, founded by 2015 World Barista Champion Saša Šestić. Distinguishing feature: roasting begins at room temperature — no pre-heat charge temperature. Fan speed calibration for altitude compensates for changes in atmospheric density. Official sample roaster of the WCRC 2024–2027. LINK Studio software (1,000+ profiles) is hosted on Kaffelogic’s servers, reflecting the deep Kaffelogic–Nucleus technical partnership. See Nucleus Coffee Tools and Sample Roasters. (source: Nucleus Coffee Tools (website))
Behmor Jake
Home/prosumer drum roaster from American manufacturer Behmor (Incline Village, Nevada). Up to 1 kg capacity; minimum 100 g (sample-capable). Artisan Roasting Software compatible via USB; bean mass thermocouple for direct temperature readings. Behmor’s patented smoke suppression (electric thermal afterburner with quartz elements) is the company’s core innovation — it enables indoor roasting without a ventilation flue, which is standard on all Behmor machines. The Jake sits below the specialty sample roaster tier (ROEST, IKAWA, Kaffelogic) in thermal precision and software ecosystem, but represents the top of Behmor’s home/prosumer line. Behmor also produces the 2000AB Plus (up to 1 lb / 454 g, 5 pre-set profiles, no USB), aimed at home users. See Behmor. (source: Behmor (website))
Fresh Roast SR540 / SR800
Consumer-tier fluid-bed roasters from American manufacturer Home Roasting Supplies (Henefer, Utah; founded 1995). The SR540 roasts 120 g (334). Both share 9 heat levels, 9 fan levels, a real-time temperature display, and a transparent glass roasting chamber — but are manual-analog only with no profiling software integration (no Artisan, no Cropster). 120V North American only. Below the Behmor Jake in specialty features; not relevant for professional sample roasting programmes. The SR800 is the most affordable significant-capacity home fluid-bed roaster currently available. (source: Home Roasting Supplies (website))
Tier 2 — Artisanal and Production Drum Roasters (1–30 kg)
Production drum roasters in the 1–30 kg range are the core machines of specialty micro-roasteries and established artisanal roasters. They share the same heat transfer principles as classic and indirectly heated drums, but are built for multi-batch production rather than sample work. All major manufacturers offer steplessly adjustable airflow, gas/electric variants, and data-logging software integration.
Giesen (Netherlands)
Dutch manufacturer (est. 2006, Dinxperlo); rebranded as Giesen Roasting Solutions in 2025. Family-owned; purpose-built facility in Dinxperlo. All machines are drum roasters (gas or electric). (source: Giesen (website))
| Model | Batch size | Throughput |
|---|---|---|
| WPG1 | small (specs not published) | — |
| W1A / W1E | ~1 kg | — |
| W6A / W6E | 3–6 kg | up to 24 kg/h |
| W15A / W15E | 15 kg | up to 75 kg/h |
| W30A / W30A Pro | 30 kg | up to 150 kg/h |
| W45A–W140A Pro | industrial | fully automated |
W30 and above include an external cyclone as standard. Software: Giesen Profiler (free; Smart Triggers; manual + automatic modes) and Giesen.Cloud (cloud dashboard for inventory, profiles, planning, live monitoring). See Giesen for full profile.
Relevance to Kaiserblick
Roxanne Fredericksen manages roast profile development at Kaiserblick’s roasting operation. The machine type directly determines the charge temperature range, feasible roast times, and the degree of airflow control available for managing ROR and DTR. A single-pass indirectly heated drum roaster with data-logging software (Cropster or equivalent) is the configuration best suited to Kaiserblick’s light-to-medium micro-lot roasting philosophy.
A compact sample roaster (ROEST, Kaffelogic Nano 7e, or Aillio Bullet) alongside the production machine enables iterative profile development without consuming production capacity — see Sample Roasters.