Development & the drop
The last few minutes decide the roast. Once first crack begins you're in the development phase — a short, high-leverage window where you set the final character and then choose the exact moment to stop. Get this right and a good green becomes a good cup.
What "development" actually means
Development isn't just "time after first crack." It's whether the reactions inside the bean have had enough time and energy to finish their work — converting and softening acids, building sweetness and body — all the way through to the bean's core, not just its surface.
- Under-developed: the outside is roasted but the inside lags. The cup is sour, sharp, grassy, with a tell-tale baked-bread or raw-peanut edge.
- Over-developed: pushed too long or too hot, the bean trades its acidity and nuance for flat, generic roastiness.
The art is landing in between — and that target moves with the coffee and the cup you're after.
Development Time Ratio (DTR)
The headline number roasters use to track development is the Development Time Ratio: the share of the whole roast spent after first crack.
DTR = (total time − first-crack time) ÷ total time × 100%
So if first crack starts at 8:00 and you drop at 10:30, development is 2:30 of a 10:30 roast — a DTR of about 23.8%. Most balanced roasts land in the 18–25% range; bright light roasts sit lower, espresso and darker styles higher.
DTR is a guide, not gospel
Treat the number with healthy skepticism:
- It depends entirely on when you call first crack — and that's a judgment call that varies between people and machines.
- It ignores the shape of the roast. A crashing, flicking roast with a "perfect" 22% DTR still tastes muddy. A clean RoR matters more.
- It varies by bean: dense high-grown coffees often want more; soft naturals less.
Its real value is as a comparator between your own roasts. Same coffee, same machine, nudge the DTR up two points, taste the difference — that's how you learn what a given coffee wants.
Knowing when to drop
The drop is the moment you end the roast and rush the beans into cooling. Good roasters integrate several signals at once:
| Signal | What it tells you |
|---|---|
| Clock / DTR target | Your planned development window for this coffee |
| Color | How dark the surface has gone — pull a few beans to check |
| Smell | Sweet and roasty (good) vs. acrid and smoky (too far) |
| Sound | How far past first crack you are; whether second crack is near |
| Intent | Bright filter wants less; rich espresso wants more |
Then cool fast. Beans hold a lot of residual heat and keep roasting in the tray, so the quicker you drag the temperature down, the more precisely you hit the level you aimed for. On most home setups that means a colander and a fan — on the Nano it's automatic: the machine runs a forced-air cool-down for you the moment the profile ends.
Because the Nano runs a designed profile, you effectively pre-decide development by shaping the curve and setting the total time — then it cools automatically. You can still extend or shorten on the fly, but the mindset shifts from "watch and react" to "design, then refine." Exactly how is covered in Part IV.
That's the anatomy of a roast end to end. Now let's go inside the bean and ask where the flavor actually comes from.