24 August 2026 · 5 min read
on our coffee's card you can sometimes see a roast graph — a curve creeping upward. to some it's just a «nice line for gravitas», but it's really the recipe by which a green bean became exactly this taste. let's unpack what's happening there and why we take each batch's profile so seriously — without getting too technical, just so you understand what you're paying for.
what's actually going on in the drum
roasting is the controlled delivery of heat into the bean over roughly 8–14 minutes. raw green beans are hard, moist and smell of grass; heat carries them through several phases. the curve on the graph is mostly the temperature of the bean itself (bt, bean temperature) over time, and the shape of that curve decides where the flavour goes.
the drying phase
the first third of the roast. moisture leaves the bean (~10–12%), it turns from green to yellow and smells of hay or fresh bread. chemically almost nothing «tasty» has been born yet — this is preparation. get this phase wrong (too fast or too slow) and everything after is spoiled, however hard you try later.
the maillard and caramelisation phase
the bean browns, and this is where flavour is born: maillard reactions (between sugars and amino acids) and the caramelisation of sugars give thousands of aromatic compounds — from nut and bread to caramel and chocolate. it's the «golden» phase where body and sweetness are laid down.
first crack
at a certain point the bean cracks loudly, like popcorn — that's «first crack» (FC). pressure from water vapour and gases has built up inside and the bean's structure opens. FC is the key reference point of the whole roast: everything BEFORE it is preparation; everything AFTER is the «development time», which largely decides the final taste.
ror — rate of rise
rate of rise shows how fast the bean temperature climbs each moment — the «acceleration» of the roast. on the graph it's the second, declining line. in a healthy roast the ror falls smoothly and evenly from start to finish. if it suddenly jumps or «collapses» around first crack (roasters call it crash / flick), defects appear in the cup: underdevelopment, a «baked» flat taste, dulled sweetness. a smooth, controlled ror is a sign of a clean, skilful roast.
development time (dtr)
development time ratio is the share of time AFTER first crack out of the total roast time. a rough intuition: a shorter development → brighter acidity, more «origin» and fruit, but a risk of underdevelopment (grassy, sharp, «green» notes); a longer development → more sweetness, caramel and body, less acidity, but a risk of a «flat» or «baked» taste if pushed too far. the whole art of the roaster is finding the balance for this specific lot, because there's no ideal DTR «for everyone».
drop temperature
the moment the beans are tipped from the hot drum into the cooler. literally a few degrees' difference and the same lot becomes lighter and more acidic or darker and sweeter. it's the final touch, the comma in the sentence of the profile.
why one lot yields a dozen tastes
by changing these parameters — the pace of drying, the point and «force» of first crack, the development time, the drop temperature — the roaster «develops» different sides of one and the same bean, the way a photographer develops film. from one green lot you can draw out florals and citrus, or caramel and chocolate. that's why not just the farm and variety matter, but the hands and decisions of whoever roasted it; it's the answer to why the same kenya tastes different from different roasters.
why this matters to you as a buyer
you don't need to read the graph like an engineer. it's enough to grasp the main thing: behind the taste in your cup is a deliberate decision, not chance. and to have a few markers for diagnosis: if coffee is «green», grassy, sharply sour — it's likely underdeveloped; if «flat», ashy, bitter no matter how you brew it — it's over-roasted or scorched. and the roast date is a reminder that even the best curve doesn't live long without freshness.
in short
the roast curve is the maker's signature under the bean. it explains why the same region tastes different from different roasters, why roasting is a craft and not «heating until brown», and why we control each batch's profile so meticulously. next time you see that graph on a card — you'll know what stands behind it.