Glossary¶
Terms used throughout this documentation. Definitions are given as they apply inside TilauScope, which is not always the widest possible sense of the word.
Note
This glossary grows with the documentation. Every chapter that introduces a term defines it here and links to it on first use.
Roast phases and milestones¶
CHARGE¶
The moment the green coffee is dropped into the drum. It is the origin of the roast clock: every phase duration and every milestone time is counted from it.
TP — turning point¶
The lowest bean temperature of the roast, reached shortly after charge, when the beans stop absorbing heat faster than the machine supplies it and start climbing again. A rising RoR after TP is normal recovery, not a fault.
Drying — DRY¶
The first phase, from CHARGE to dry end. Free moisture leaves the bean. Little colour develops.
DE — dry end¶
The end of the drying phase. In TilauScope it is a marked milestone, detected and proposed for confirmation, and one of the anchors the roast plan is built around.
Maillard¶
The middle phase, from dry end to first crack. Sugars and amino acids react and produce most of the roast's aromatic complexity. The phase where heat reductions are staged.
These reactions absorb heat rather than release it, so the burner is feeding them, not merely warming the bean. Cutting the heat here does not slow the reaction gently — it starves it, and the bean temperature keeps climbing on the drum's own heat while the chemistry stalls. This is why the plan holds the heat through Maillard instead of stepping it down early, and why it is a phase to judge by the settings held rather than by the curve. See baked.
FC — first crack¶
The audible cracking as bean structure fails under internal pressure. It marks the start of development and is the single most important milestone for reproducibility — which is why TilauScope learns its temperature from your own roasts.
Development¶
The final phase, from first crack to DROP. Determines much of the cup's balance and body. Measured relative to the whole roast as DTR.
DROP¶
The moment the beans leave the drum for the cooling tray. The end of the roast.
Back-to-back¶
Roasting a second batch immediately after the first, while the machine is still hot. It needs different handling from a cold start, which is why TilauScope has a dedicated mode for it.
Measurements¶
BT — bean temperature¶
The probe reading closest to the beans themselves. Every temperature in this documentation is a bean temperature unless stated otherwise.
ET — environmental temperature¶
The probe reading of the air or the drum environment. On some machines — radiant ones in particular — ET can sit below BT, which is normal for that machine type and not a fault.
RoR — rate of rise¶
How fast bean temperature is climbing, in degrees per minute. The slope of the curve rather than its height. A roast is steered largely by keeping RoR inside a sensible band and falling smoothly.
DTR — development time ratio¶
The share of total roast time spent in development, as a percentage. A common target sits somewhere between the high teens and low twenties, depending on the coffee and the intended cup.
Charge weight — green weight¶
The weight of green coffee going into the drum. It sets the whole scale of the roast: phase durations, how much heat the batch can absorb, and what counts as a comparable previous roast when TilauScope looks at your history.
Weight loss¶
The weight the batch lost during roasting, as a percentage of its charge weight. Mostly water early on, then organic matter as the roast develops, so it tracks how far the roast went.
Moisture content¶
The water still held in green coffee, as a percentage of its weight. Higher moisture means a longer drying phase and a coffee that resists heat for longer at the start.
Density¶
How much the beans weigh for a given volume. Dense beans conduct heat inward more slowly and need sustained heat; light, low-density beans take heat faster and are easier to scorch.
Agtron¶
A numeric scale for roast colour: the lower the number, the darker the roast. TilauScope uses it as the target you aim for, and — where a colour reader is fitted — as the measurement you compare against.
SCA score¶
A cupping score out of 100 following the Specialty Coffee Association protocol, used as the standard reference for a coffee's quality independent of any particular roast.
aw — water activity¶
How much of the water in green coffee is chemically available, on a 0 to 1 scale. It predicts how well a bag will keep far better than moisture content alone.
Retained reading¶
A network sensor's last published value, kept by the message broker and handed to TilauScope the moment it starts listening. Without it a channel stays empty until the sensor next speaks of its own accord, which on a home automation network can take minutes.
TLS¶
The encryption a message broker can require on the link, so that readings and the password used to obtain them do not travel in clear text. The broker proves its identity with a certificate, which must come from a recognised authority: a certificate the broker issued to itself is refused, and the connection simply fails.
Keepalive¶
The idle time after which a quiet connection to the broker is checked. Short values notice a broker that has gone away sooner, at the cost of talking to it more often.
Polling¶
Asking a network sensor for a reading instead of waiting for one. Some sensors report only on their own schedule, far too slowly to follow a roast; polling requests a fresh value at a chosen interval. Only sensors on mains power can be polled — a battery sensor sleeps between its own reports and cannot be reached in between.
Machine behaviour¶
Thermal mass¶
How much heat the machine's own metal stores. A high-thermal-mass drum keeps delivering heat after the power is reduced, so reductions must be made earlier to land on time.
Radiant heat — FIR/NIR¶
Heating by infrared radiation rather than by hot air. Radiant machines transfer heat to the beans very directly, which changes both how fast they respond and how their two probes relate to each other.
PID¶
A control loop that holds a temperature at a target by continuously adjusting power. TilauScope uses one to bring the machine to its preheat target.
SV — setpoint value¶
The temperature a PID is aiming for.
Overshoot¶
Sailing past the target temperature because the machine's stored heat keeps arriving after the power has been cut. The higher the thermal mass, the more of it there is, and the earlier the power has to come off to avoid it.
Storage¶
Conditioning¶
How a bag of green coffee is sealed: vacuum, valve bag, sealed jar, open cloth bag, and so on. It decides whether the coffee drifts toward the room's humidity or holds its own water activity — sealed methods hold it, an open bag drifts.
Equilibrium moisture content — EMC¶
The moisture a bean would settle at if left in the current room conditions indefinitely. A rough guide for what an open bag is drifting toward, not a measurement of the bean itself.
Brewing¶
Degassing¶
The release of CO₂ trapped in a bean by roasting. A coffee brewed too soon, before it has degassed enough, pushes back against water unevenly and extracts unpredictably — which is why a coffee needs a few days' rest before it brews at its best.
Extraction yield — EY¶
The share of the ground coffee's mass that ends up dissolved in the cup, as a percentage. Too little tastes thin and sour; too much tastes bitter and harsh — dialling in means steering toward the range in between by adjusting grind, ratio or time.
Channeling¶
Water carving a fast path through the coffee bed instead of passing through it evenly — part of the bed is over-extracted, part under-extracted, at the same time. A grind change alone does not fix it; it is a distribution or preparation problem.
Faults and risks¶
Crash¶
An abrupt collapse of RoR, usually just after first crack, when the roast loses momentum. Left alone it leads to a baked cup.
Flick¶
The opposite of a crash: RoR turning back upward late in the roast, usually producing harsh, ashy notes.
Baked¶
A flat, hollow, bread-like cup, caused by spending too long in a phase with too little thermal momentum — most often a drying or Maillard phase that ran long, or one run on too little heat.
The second case is the harder one to see: because the drum keeps radiating, bean temperature and RoR can both look impeccable while the reaction underneath has already stalled. A smooth curve is not proof that the roast is being fed.
Flash drying¶
Drying driven so hard that the bean surface dries far ahead of its core, leaving the roast unevenly developed.