Charge Temperature Guidelines
Charge temperature is one of the fastest ways to change roast momentum, early heat uptake, and cup character on Roest machines. The main question is not “what is the correct charge temperature,” but which temperature reading is being used, how stable the machine is at charge, and how the setting fits the batch size, process, and profile style. This guide summarizes practical starting points and adjustment logic for Roest L100/S100/Ultra/P3000-style roasting without replacing the linked pages on batch-size scaling, inlet temperature management, cooling and between-batch protocol, and heat-transfer fundamentals.
Define the Temperature Before Comparing Numbers
On Roest, “charge temperature” must be qualified. Tom from Roest states that when he talks about charge temperature, he means drum temperature source. Community profiles, especially older ones, may instead describe the charge by ET, air temperature, inlet temperature, preheat temperature, or a displayed profile setpoint.
This distinction is not cosmetic. A 200–230°C ET or air charge can correspond to a much lower drum temperature on Roest; examples include 200°C ET with a drum around 120°C, 215°C ET corresponding to about 155°C drum on one setup, and 250°C charge producing different drum temperatures on different Roest generations or configurations 2 sources. Before copying a profile, the operator should identify whether the number refers to drum, ET, inlet, air, or BT.
Practical Starting Points
The following values are starting points, not universal rules. They assume the machine has been warmed and reset consistently; for the between-batch workflow that makes this repeatable, use Cooling and Between-Batch Protocol. Charge temperature should be adjusted together with batch size, inlet/power profile, airflow, and roast-time targets rather than treated as an isolated variable.
curated Before using 175–200g sample-roaster profiles, confirm that your specific Roest model/configuration is rated for that batch size and that the cooler and chaff handling are adequate. curated Do not treat larger community batch examples as automatically transferable to every S100/L100/Ultra setup; overloading can cause poor bean movement, uneven roasting, inadequate cooling, and higher chaff/fire risk.
| Use case | Starting charge reference | Practical intent |
|---|---|---|
| 50g batches | About 128°C drum for a 50g workflow source | Small sample batches need lower thermal input and should not be scaled directly from larger-batch profiles. |
| 100g sample roasting | About 140°C drum for a 100g sample profile source | Useful for sample roasting and modulation; BT feedback may be less reliable at 50–100g on L100/S100 source. |
| 150g general starting range | 135–165°C drum, depending on bean and style; one high-volume data point reports thousands of 150g batches at 140–170°C at sea level with 3100rpm inlet fan 2 sources | Baseline range for 150g roasting when not following a more specialized low-charge or high-charge profile. |
| 150g naturals / lower-density profile | 125–135°C drum is a common starting point for lower-density or natural-focused profiles 2 sources | Keeps the start controlled for naturals that darken or run away easily; pair with the process guidance in Natural Process Roasting. |
| 150g washed / high-density light profiles | Shared washed examples often sit around 125–130°C drum and target first crack in the mid-5-minute range on 150g washed coffees 2 sources | Works as a light, high-density washed starting style when the rest of the profile supports it. See Washed Process Roasting and Kenya and Ethiopian Coffees. |
| 175–185g washed profiles | Around 150–160°C drum is a recurring working range; one 180g washed example uses 152°C drum 2 sources | Common for Denis-style larger L100/S100 batches where charge temperature is used as a taste and momentum lever. |
| 200g exploratory / high-energy Roest work | Around 180–190°C drum has been used as a starting point in 200g testing; one test used 190°C charge, 25rpm, 3400 heater fan, and 65% exhaust 2 sources | Higher batch mass usually needs more starting energy, but 200g also requires different RPM, airflow, and cooling discipline. See Batch Size Scaling. |
| P3000 | Examples range from 200–225°C drum, with Christopher charging 215–217°C depending on ambient and noting Prodigal at 225°C 2 sources | P3000 charge numbers should not be copied directly to L100/S100/Ultra. Its warmup and BBP behavior are different. |
| Ultra / L200-style references | Lower inlet and charge behavior than L100 has been reported; a 250°C charge that gave 180°C drum on L100 gave about 160–164°C drum on Ultra/current setup 2 sources | Treat Ultra profiles as their own system; avoid direct L100 charge-temperature transfer. See Roest Ultra Guide. |
After the starting point is chosen, adjust charge temperature by taste and measured outcome:
| Symptom or goal | Charge-temperature move |
|---|---|
| Cup tastes under, green, bark-like, cereal-like, or lacks formed flavor | Increase charge temperature or increase early P1 energy. Denis describes higher charge and/or higher inlets as the fix for coffees that taste under despite longer development source. |
| Cup has too much browning, caramelization, roast taste, or heavy coating | Lower charge temperature while keeping the end/drop target controlled source. |
| More body, sweetness, roundness, and robustness are desired | Charge higher and put more energy in early, rather than simply extending development source. |
| More floral, high-acid, softer expression is desired | Charge lower, accepting that very low starts can become softer, less deep, or more vegetal if taken too far 2 sources. |
| Roast speed needs a small shift after the profile already works | Raise or lower charge temperature rather than rebuilding the whole profile; Christopher describes ±25°F as a simple adjustment, while other side-by-side testing found 10°C changes tasteable 2 sources. |
Charge Temperature as a Profile-Tuning Lever
Once a profile works, several experienced users prefer changing charge temperature before rewriting the profile. Denis describes a workflow of keeping a core adaptive profile, adjusting charge higher or lower when the bean needs it, and then using drop BT or color/taste feedback for final tuning 2 sources. This is especially useful when the issue is early energy uptake rather than final roast degree.
Charge temperature can also change the roast speed without changing the rest of the power or inlet shape. Denis notes that with the same power/inlet profile, playing with charge temperature can make the roast faster or slower source. In another comparison, changing charge by 10–20°C was described as enough to steer drying timing while keeping the same inlet or power profile source.
The adjustment scale depends on which temperature is being changed. A 5–10°C change to inlet/profile points may be meaningful, while Denis treats 30–50°C as a larger charge-temperature adjustment when discussing ET-style charge numbers, not drum temperature source. This is why every profile should record which sensor the charge value refers to.
Process and Moisture Considerations
Washed, natural, anaerobic, honey, and low-density coffees do not all respond the same way. Process and moisture influence whether a coffee needs a colder start, a hotter start, a soak-like low-energy beginning, or more early heat.
For moisture-driven decisions, Denis gives the simple rule: low-moisture coffees can take a colder start, while higher-moisture coffees need a hotter start; if there is no moisture meter, ask the importer source. He applies a similar logic to high-moisture naturals, anaerobic, and soaked/processed coffees, using higher charge temperature and higher early P1 energy than for low-moisture washed coffees source.
Naturals are a major exception-prone category. Several natural/lower-density profiles start around 125–135°C drum, and some users report problems when charging naturals above about 150°C drum 2 sources. At the same time, some higher-moisture or heavy-process coffees need more early heat, and some contributors charge naturals slightly higher than washed profiles in their own systems. This is why Natural Process Roasting should be treated as a process-specific guide rather than reducing naturals to “always lower” or “always higher.”
Washed high-density coffees often tolerate, and sometimes require, a more assertive early energy strategy. Denis’s washed Kenya/Ethiopia work includes charges in the 120–140°C drum range for some light profiles, 150–160°C drum for larger batches, and higher ET-style charge adjustments when a bean tastes under or woody 2 sources. The right number depends on whether the profile is built around drum charge, ET charge, inlet/BT control, or power.
Batch Size Changes the Meaning of Charge
Changing batch size changes the thermal system, so a charge temperature cannot be moved across 50g, 100g, 150g, 185g, and 200g without changing other settings. Denis states directly that changing batch weight means adjusting inlet, RPM, exhaust fan, and other settings source. Larger batches generally need more energy at the start, while small batches can be overdriven easily source.
Small batches also make sensor interpretation harder. Denis says BT is not reliable for 50–100g on L100/S100, and 50g profiles should be treated as learning or sampling tools rather than direct production references 2 sources. For scaling across sizes, use Batch Size Scaling, Drum Speed / RPM Settings, and Airflow and Fan Settings.
Warmup, BBP, and Repeatability
Charge temperature only means something if the machine reaches the same starting condition. Starting with the same displayed ET but a different drum temperature can produce different outcomes. Sam reports that roasts with the drum slightly colder or hotter had very different outcomes, and Denis warns that inconsistent drum temperature between batches leads to false conclusions 2 sources.
A stable warmup matters. Denis commonly preheats at least 15–20 minutes, while other users report drum temperature stabilization around 15 minutes or more depending on setup 2 sources. Tom describes either idling until drum temperature stabilizes at charge temperature or running an empty warmup to heat past charge temperature before entering BBP source.
Between batches, the drum must be reset or managed to the same target. Tom’s BBP concept is that when the protocol ends, drum is at charge temperature and air is at preheat temperature source. Detailed cooldown procedures belong in Cooling and Between-Batch Protocol, but the charge-temperature principle is simple: do not compare charge-temperature tests unless the drum start condition is consistent.
Sensory Effects of Higher and Lower Starts
Across several comparisons, lower charge tends to push cups toward floral, vegetal, herbal, softer, thinner, or less mature expressions when taken too far. Higher charge tends to increase perceived fruit density, sweetness, body, caramel/brown-sugar tones, coating, and roast momentum 2 sources.
One direct comparison from Denis describes a low-charge roast as baked, flat, missing body and sweetness, while the higher-charge roast was vivid, fruity, and sweet source. Another comparison found low drum charge smelling more vivid, sour, and floral but later becoming watery/under, while higher drum charge smelled fuller and improved with more sweetness, body, and aftertaste as the cup cooled source.
These observations do not mean “higher is always better.” If the cup shows too much browning, roastiness, heavy body, or dark/sugary notes, lower the charge or reduce early heat. If the cup is green, woody, thin, empty, or underdeveloped, raise the charge or increase early energy before extending development time.
Meaningful Conflicts and Caveats
CONFLICT (Unresolved): low versus high charge for naturals. Several trusted contributors recommend lower drum-charge starts for naturals, often around 125–135°C drum, to avoid rapid darkening and process-sugar defects 2 sources. Other experiences point to higher charge or more early heat for higher-moisture, heavy-process, or naturals that absorb heat slowly, and Christopher notes that he may charge naturals a bit higher in his current starting approach 2 sources. The practical resolution is to start from the process-appropriate table above, then adjust by cup, color, moisture, and roast-time behavior.
CONFLICT (Unresolved): how much drum temperature matters in an air-dominant Roest system. Some statements emphasize that Roest is an air roaster and that drum temperature is less important than on traditional drum roasters, while others treat drum temperature as the primary repeatability variable. The synthesis is that the absolute drum temperature may not behave like a cast-drum roaster’s charge temperature, but matching drum temperature at charge is still critical for repeatable starts and useful BBP control 2 sources.
CONFLICT (Temporal / Hardware Evolution): model-to-model charge numbers do not transfer cleanly. L100, S100, Ultra/L200, and P3000 can report different drum temperatures for similar displayed charge or preheat values. Espressofun reports 250°C charge giving 180°C drum on L100 but about 160–164°C on Ultra/current setup, and Denis states that old L100 methods do not transfer directly to Ultra 2 sources. Charge guidance should therefore be treated by model and sensor, not by a single universal number.