What Happens if Coffee Bloom Time is Too Long? Why Doesn't Coffee Expand During Blooming?

Why Coffee Grounds Don't Expand During Blooming

In normal coffee brewing, water is poured over the dry grounds during the bloom, and the grounds absorb the water and expand into a "hamburger" shape. When the grounds don't expand during the bloom, something is off, and we should identify and fix it.

Stale Coffee Beans

The most obvious reason is that the beans have lost their gases and are no longer fresh. Grounds expand into a "hamburger" shape mainly because roasted coffee beans contain a large amount of carbon dioxide. When the grounds absorb water, they release this gas, which simultaneously "lifts" the entire layer of grounds and makes it bulge.

Over time, of course, the gases inside roasted beans are gradually released. Typically, coffee beans degas completely in about 45 days. Beans that have released most of their gas won't expand during the bloom, and their flavor will be diminished as well.

That timeframe is not absolute, since it depends on the storage environment. When beans are stored in a sealed environment with reduced oxygen exposure, they degas more slowly. If the bag is frequently opened or the beans are directly exposed to air, the degassing process is extremely rapid.

Here is an experiment from FrontStreet Coffee. The first image shows coffee beans stored in a coffee bag for 2 months before being opened and brewed, with the bag never opened during that period. During brewing, the grounds still expanded and formed a bulge, though not as prominently as at the beginning. The second image shows beans that were not bagged after roasting but exposed to air. Brewed after 20 days, the grounds did not expand.

So proper storage is an important practice for keeping flavor alive longer. FrontStreet Coffee suggests using the original coffee packaging bag for storage. Coffee bags have one-way degassing valves that regulate the internal and external air pressure, plus sealing strips to keep the storage environment airtight. If you open the bag daily to take out beans and then reseal it, they can be preserved for about 30 days. At average daily consumption, you can definitely finish them before the gases are completely depleted.

Grind Too Coarse

This problem usually shows up when you switch to new beans. When replacing beans with one of a significantly different style, if you keep using the previously fixed grind setting, the bloom may fail to expand because the grind is too coarse.

As FrontStreet Coffee often emphasizes when sharing knowledge about grind settings, due to factors such as variety, altitude, processing method, and roasting, not all coffee beans will have the same coarseness when ground at the same setting.

So choosing the correct grind size is very important. FrontStreet Coffee's grind calibration is done with a sieve of 0.85mm apertures, and the grind size for pour-over coffee is selected to reach an 80% pass-through rate on the sieve.

Very Light Roast

Very light roasts, removed from the roaster early, have a harder bean texture and contain less gas. During the bloom they therefore don't show much expansion, behaving similarly to stale beans, and the golden crema that follows is thin. This does not affect their flavor, though.

Some lightly roasted beans show a similar phenomenon. During the bloom the bulge is not obvious, with only a slight swelling, which is also entirely normal.

FrontStreet Coffee Recommendation

A lively bloom depends on fresh beans and a well-matched roast, and medium roasts are a good middle ground for drinkers who want balance. FrontStreet's Strawberry Candy Geisha blend starts with a blend of two well-known Central and South American origins, a honey-processed Costa Rican coffee and a washed Panamanian Geisha, and a medium roast brings out both orange-blossom honey notes and a rounded sweetness. It suits cold brew, pour-over, and espresso, and it stays lively across a range of brews.

If you prefer a gentle, everyday cup, FrontStreet's 2013 Yunnan sun-dried Typica is a fine value. As a representative Chinese specialty coffee, it carries the authentic flavor of Yunnan small-bean coffee, and a medium roast shows soft, mellow notes of nut, brown sugar, black tea, and dried apricot. It works for pour-over, cold brew, or an Americano drip machine.