The question comes up almost every weekend at the stall: I just bought the bag, can I brew it at lunch? You can. Coffee is drinkable two hours after it leaves Golden. The question that changes something in the cup is how long to rest coffee after roasting so it gives everything it has, and the answer depends on the method you use at home.
How long to rest coffee after roasting: what happens inside the bean
Roasting creates carbon dioxide inside the bean and the gas stays trapped there. From the moment the beans leave the drum it starts to escape: fast in the first hours, then slower and slower, for weeks. Samo Smrke, Chahan Yeretzian and colleagues published a gravimetric method in the Journal of Agricultural and Food Chemistry on 1 November 2017 that measures this release in real time: the speed matters for packaging, crema and extraction.
In the cup, that gas does two things. It lifts the coffee bed and keeps water away from the particles, so extraction turns uneven and the taste thin. In espresso it swells the puck and lets water run around the edge: the shot gushes and comes out sour.
How long to rest coffee after roasting, method by method
The numbers below are the starting points most roasters work with. Count the days from the roast date printed on the bag.
- French press and cezve: from 2 days. Immersion forgives the gas, since the water sits with the coffee for the whole brew.
- Filter, V60, Chemex, AeroPress: from 4 days, with the best stretch between day 5 and day 14.
- Espresso and moka pot: from 7 days. Many baristas prefer espresso in the second or third week.
- Cold brew: between 10 and 14 days.
Roast level moves the window. A lighter roast holds the gas longer and asks for a few extra days. A roast taken further leaves the bean more porous, the gas leaves faster and the window opens two or three days earlier.
The bloom test: how long to rest coffee after roasting, measured in 30 seconds
Grind 15 g, pour 45 ml of water at 93°C (199°F), three times the weight of the coffee, and start the timer.
- The foam swells hard and cracks around 20 seconds: the batch is still full of gas. Leave the bag another 2 or 3 days, or hold the bloom for 45 seconds before you pour the rest of the water.
- The foam rises calmly and settles around 30 or 40 seconds: you are inside the window.
- The foam barely moves: the gas is gone. Grind one step finer and take the water to 94°C (201°F).
The test costs 15 g of coffee and tells you where your batch sits, with your grinder and your water.
How long to rest coffee after roasting when the batch comes off an open air fire
The window depends on how far the batch went in the drum, and Laurent decides that outside, on the spot: he reads the morning air, then adjusts the fire and the time on Golden. Today's forecast gives Saturday 26 September 14 to 21°C (57 to 70°F), 59% average humidity and gusts up to 33 km/h (21 mph), and Sunday 27 September 13 to 24°C (55 to 75°F) at 73% humidity. In damper air the drying phase runs longer and Laurent keeps the fire higher at charge, so Sunday's batch can come out a shade different and two bags of the same origin can open their window a day apart.
That is why the bag carries a one way valve: it lets the gas out and keeps oxygen outside. Press the bag with your palm before you open it. If air comes through the valve smelling of fresh coffee, the batch is still degassing and has days to go. If the bag stays soft and gives nothing back, you are near the end of the window.
How long to rest coffee after roasting: troubleshooting case by case
- An espresso that runs in 15 seconds and tastes sour, two days off the roast: give the bag 5 more days, then touch the grinder. The rest of the mechanism sits in the piece on grinding too fine.
- A filter brew with big bubbles lifting the bed and water escaping around the edge: bloom for 45 seconds, using double the coffee weight in water.
- Three week old coffee that tastes flat: one step finer and water at 94°C (201°F). Check the dose on a scale too, since a spoon measures volume and that shifts from batch to batch.
- A bag kept in the fridge: take it out. Condensation lands on the beans at every opening. Cupboard, room temperature, bag rolled shut, valve clear.
How long to rest coffee after roasting, tested Saturday and Sunday at the Marché de l'Abattoir
We roast on Saturday and Sunday, in the open air, at the Marché de l'Abattoir, by the exit of the Manufakture car park in Anderlecht. Ask Laurent to write the hour next to the roast date. Run the bloom test on day 3 and on day 7 from the same bag, then tell him the following weekend which one you preferred. This weekend's coffee is waiting at the stall and in the shop.
Brut. Sauvage. Imprévisible.
