Does Coffee Need to Rest After Roasting?

Buying your Specialty coffee as close to its roast date as possible, you might assume it should be brewed straight away. Freshness matters, but coffee often benefits from being left for a short period before brewing – this is what’s known as ‘resting’.

During roasting, browning reactions produce a large amount of carbon dioxide (CO₂). Some gas escapes in the roaster, but much of it remains trapped inside the bean.

Over time, this CO₂ slowly leaches out in a process called ‘degassing’ (if you’ve ever noticed one-way valves on your coffee bags, they allow the gas to escape after roasting). Letting this process take its course prevents CO₂ from disrupting extraction.

So, how long should coffee rest after roasting? Unfortunately for home baristas, there’s no one perfect time for every coffee. How long you should leave it depends on the coffee itself, whether you’re brewing filter coffee or espresso, and even the climate you live in.

Why do you need to rest coffee?

Resting coffee gives some of the CO₂ trapped inside the beans time to escape.

If there’s still a lot of CO₂ trapped in the coffee when water hits it, the gas can interfere with extraction as it is hydrophobic (repels water). As CO₂ works its way out of the grounds, it creates bubbles that temporarily push water away from the soluble parts of the coffee, which makes it harder for the water to extract those flavour compounds.

With filter coffee, you can easily see this escaping CO₂ during the bloom, when the grounds swell and bubbles appear as water is poured over them.

For espresso, excess CO₂ can cause more trouble. The gas pushes back as water hits the coffee, which makes it harder to extract properly. Brew too soon, and your final cup might taste unpleasantly sour, highly acidic, or noticeably under-extracted.

To sum up: the point of resting coffee is to allow enough gas out to make it easier to brew, without letting real staling reactions take place.

What affects how quickly coffee degasses?

Resting times won’t be the same for every coffee – different factors can affect how quickly coffee releases trapped CO₂.

Roast level

The darkness of a roast impacts how beans hold carbon dioxide.

Lighter roasts, for example, produce less CO₂, but the resulting bean is much denser, meaning the trapped gas takes longer to escape. Dark roasts generate more CO₂, but the longer roasting process makes the beans more porous and brittle.

Darker beans can’t hold onto the gas, so it escapes more easily.

Coffee density

The physical structure of the seed is equally important. Coffees grown at higher altitudes naturally produce denser seeds, and because of this tight cellular structure, denser coffees will always degas more slowly.

Storage temperature

Your ambient storage environment directly alters the degassing speed.

Warmer environments cause coffee to degas quicker, which should shorten the waiting period. In the same way, keeping beans in cooler environments (e.g., a basement or freezer) slows outgassing down.

How should you store coffee while it rests

While your coffee rests, keep it sealed. If you’re buying specialty, roast-to-order coffee from Bold Street Coffee, the one-way valve on our bags facilitates this process by allowing trapped CO₂ to escape without letting fresh oxygen in.

In an ideal world, you should store the sealed beans in an ambient environment of around 20°C – we advise against placing them anywhere warm, as this will only unnecessarily accelerate the degassing process and promote unwanted staling reactions.

For Bold Street Coffee specifically, we recommend allowing your coffee to rest for at least two weeks from the roast date before brewing for the best results. If you store coffee somewhere cooler, it may need to rest a little longer before brewing.

Should you buy whole coffee or pre-ground?

If possible, buy your coffee whole and grind only what you need just before brewing. Grinding increases the surface area exposed to air, so CO₂ escapes faster, and the coffee loses freshness more quickly.

Keeping your coffee whole while it rests slows this process and preserves more aroma and flavour until you’re ready to brew. When it’s time to make your coffee, grinding it right before brewing should give you a fresher, more consistent cup.

How can you tell if coffee is too fresh or has rested too long?

There are a few signs. If you’re brewing filter coffee, for example, a very fresh roast will produce a particularly active, large bloom as the trapped gas escapes. In the cup, this can manifest as an unpleasant sour taste, sometimes likened to an acidic tang.

Espresso can be more sensitive. Brewing coffee that’s too fresh makes extraction difficult, which leads to much less consistent shot times. Generally speaking, coffee that’s too fresh will taste sour, and espresso that’s too old may produce little or no crema.

But rather than focusing entirely on a fixed number of days, it’s best to use these physical and tasting signs alongside the roast date to find the best resting period.

Brew better coffee at home with Bold Street Coffee

Resting coffee shouldn’t be a source of stress for home baristas – it’s just there to make your coffee easier to brew and stop trapped CO₂ from disrupting your extraction with unpleasant sourness.

Ready to put this into practice? Explore our range of specialty beans at Bold Street Coffee. We roast all our coffees to order and ship them in sealed, recyclable bags with one-way valves.

We ship whole beans for those who want full control over their resting and grinding, or we can grind them specifically for your V60, Aeropress, French Press, or home espresso machine before we send them out.