Two numbers on a bag matter more than almost anything else printed on it: the roast level and the roast date. Both are routinely misread.
Roast levels, briefly
Roasting is a series of chemical transitions, and the named levels are landmarks along it.
Light (City) — dropped shortly after first crack, around 196–205°C bean temperature. Highest acidity, most origin character, lightest body. Little to no surface oil.
Medium (City+/Full City) — a little further, 210–219°C. Acidity moderated, sweetness developed, more body. The broad middle where most specialty coffee sits.
Medium-dark (Full City+/Vienna) — into or just past second crack, 220–230°C. Caramelisation dominates, acidity drops sharply, body peaks. Some surface oil. This is where traditional Vietnamese roasting lives.
Dark (French/Italian) — well past second crack, 230°C+. Roast character overtakes origin character. Oily surface, thin body despite the intensity, and pronounced bitterness.
The distinction that matters is between medium-dark and dark. They are frequently conflated and they are not the same thing.
Why Robusta takes it darker
This is not a stylistic preference. It follows from the chemistry.
Robusta has roughly twice the chlorogenic acid of Arabica, about twice the caffeine, and less sugar — 3–7% against Arabica's 6–9%.
Roast Robusta light and you get the raw version of that: harsh chlorogenic acid, no caramelisation to balance it, and often a distinctly green, peanutty note. Light-roasted Robusta is genuinely unpleasant more often than not, and this is why.
Take it further and the chemistry turns. Chlorogenic acids break down into simpler, less bitter compounds. What sugars there are caramelise. Body develops. Medium-dark is where Robusta becomes what it can be — sweet, thick, chocolatey.
Arabica does not need this and is damaged by it. Its acidity and floral aromatics are the point, and they are exactly what a dark roast destroys. A 1,600 m Cầu Đất Arabica roasted dark is an expensive way to make ordinary coffee.
So: dark-roasting Robusta is a technique. Dark-roasting good Arabica is a waste. Same action, opposite verdict.
Where dark roasting goes wrong
The bad version is real and worth naming.
For a century, commodity Vietnamese Robusta arrived at roasteries full of defects — strip-picked unripe, ground-dried — and dark roasting was the fix, because past a certain point everything tastes the same. That is the practice that gave Vietnamese coffee its reputation for tasting like burnt tyres.
The difference between the two is entirely upstream. Medium-dark applied to hand-picked, honey-processed cherry is developing something that is already there. The same roast applied to defect-laden commodity green is camouflage.
The tell is in the cup: a good medium-dark is sweet with bitterness as structure. A defensive dark roast is ashy, flat and one-dimensional, with no sweetness underneath.
The same logic applies to butter-roasting, which is a genuine technique that was also widely abused.
Roast level by coffee
| Coffee | Roast | Why |
|---|---|---|
| Traditional Robusta | Medium-dark | Caramelisation, body, stands up to condensed milk |
| Honey Robusta | Medium to medium-dark | Enough development for sweetness, not so much it buries the honey character |
| Anaerobic / co-ferment | Medium | Fermentation-derived fruit is heat-sensitive; dark roasting erases it |
| Highland Arabica | Light to medium | Preserves acidity and terroir |
| Liberica | Medium | Keeps the jackfruit legible while developing molasses sweetness |
Note the pattern: the more work processing did, the lighter the roast should be. There is no point spending three days in a fermentation tank creating esters and then roasting them off.
Freshness, and the degassing window
Roasting generates enormous amounts of CO₂, and freshly roasted beans are saturated with it. That gas has to leave before the coffee brews properly.
Days 0–2: too fresh. CO₂ disrupts water contact with the grounds, extraction is uneven, cups come out sour and thin and inconsistent. Espresso gushes or channels.
Days 3–14: the window for filter brewing. Enough gas gone for even extraction, all the aromatics still present.
Days 7–21: the window for espresso, which wants more degassing than filter.
Weeks 4–6: still good, gradually flattening. Aromatics fade first, then sweetness.
Beyond 8 weeks: drinkable, not exciting. Stale coffee is not harmful, just dull.
Darker roasts degas faster because more of the gas escaped during roasting, so a medium-dark Robusta is often ready at day three where a light Arabica wants a week.
The practical test is the bloom. Wet fresh grounds and they swell and hiss. Wet stale grounds and they sit there. It costs nothing and tells you more than any date.
Roast date versus best-before
A roast date is a fact. A best-before date is a policy.
A roaster printing "roasted 14 March" is telling you something checkable and committing to turning stock over. A roaster printing "best before March 2027" is telling you nothing at all, and the twelve-month horizon suggests they do not expect the bag to move quickly.
Buy on roast date. If there is no roast date, assume the coffee is older than you would like.
Storage
Sealed container, room temperature, away from light. That is genuinely all.
Do not refrigerate. Repeated condensation on the beans is worse than the oxygen you are avoiding.
The freezer is fine for long-term storage if the coffee is properly sealed and you thaw the whole bag once rather than dipping into it repeatedly. Freeze in portions if you must.
Buy whole bean and grind to order. This matters more than everything else on this page combined. Ground coffee loses most of its volatile aromatics within fifteen to thirty minutes. A two-week-old whole bean ground fresh beats a two-day-old pre-ground every single time.
