Front Street often encounters many pour-over beginners who ask a question: Why does pour-over coffee need blooming?

The most indispensable step in pour-over coffee is the blooming phase. The purpose of blooming is to allow the coffee to release gases and ensure even extraction, and it also gives a clear indication of whether the beans being brewed are fresh. Front Street specializes in freshly roasted coffee beans. Some people mistakenly think that fresh coffee beans mean freshly ground coffee, but this is actually a concept swapped by certain merchants' marketing tactics. However, coffee beans are not better the fresher they are. If you get beans that have just been roasted, they still need to rest for four or five days so that the coffee's flavors can be fully extracted during brewing. The coffee beans Front Street generally provides are at two to three days from the roast date, unless a customer requests same-day roasted beans, in which case they will be provided additionally.

Purpose of Blooming

Blooming, often expressed in English as Bloom, refers to the preparatory action of evenly moistening the surface of the coffee grounds with a small amount of hot water before the formal pouring begins in pour-over brewing.

Front Street has demonstrated through experiments that without blooming, the brewed coffee is prone to underextraction. This is because during coffee extraction, especially with fairly fresh beans, there is a relatively large amount of gas inside the beans, and blooming is mainly meant to allow these gases to be expelled. Without blooming, the gas inside the coffee grounds begins to release in large amounts as soon as it contacts water. If brewing proceeds directly, because the gas surrounds the coffee grounds, water finds it difficult to contact the coffee grounds and can only extract the more surface-level coffee, continuously washing the extractable portion, which easily leads to uneven extraction.

Factors Affecting Blooming

Storage time of the coffee beans, roast level of the coffee beans, water temperature, water amount, blooming duration, grind size.

[Storage Time and Roast Level of Coffee Beans]

In two situations, the expansion during blooming will be不明显 or even show no reaction: freshness and roast level.

First, fresh coffee grounds contain a certain amount of gas. The gas inside the coffee grounds will gradually escape over time, and the coffee grounds will absorb some moisture from the air, causing the original gas to decrease. Therefore, stale roasted beans are less likely to expand or may even show no reaction.

Second, light-roasted coffee beans also tend not to expand too dramatically, because light-roasted coffee beans have a denser texture, so the overall gaps are not as numerous as in medium or dark roasts, and therefore they contain less gas.

[Water Temperature for Blooming]

The water temperature affects the dissolution efficiency of the entire coffee. The higher the temperature, the faster the dissolution rate, and the more soluble substances dissolve within the same extraction time. So generally speaking, if the water temperature is too high, above 95°C, it easily causes burnt bitterness and miscellaneous astringency to dissolve out quickly. The lower the temperature, the slower the dissolution rate, and the fewer soluble substances dissolve within the same extraction time. So generally speaking, if the water temperature is too low, the coffee tends to be thin, good flavors are not easily extracted, and blooming is also not easily completed.

[Amount of Water Poured in Pour-Over]

Too little water for blooming will result in the coffee grounds not being fully saturated, and the coffee will have an obvious rough astringency on entry with a short finish. If there is too much water for blooming, the hot water in the blooming phase will not have extracted enough coffee components in the early stage, and the extracted coffee will taste relatively one-dimensional, with the acidity extracted in the early stage becoming明显 prominent, thereby masking other flavors.

[Duration of Blooming]

The duration of blooming should depend on the freshness and roast level of the beans. Generally speaking, the blooming time is about 30 seconds to 60 seconds. When the expansion on the surface of the coffee grounds returns to a calm state and the surface is about to shrink, it means blooming is complete and the first pour can begin.

When Front Street Coffee brews beans that have rested for four or five days, the blooming time is generally around 30 seconds.

[Pour-Over Coffee Grind Size]

The coarseness of the coffee grind also affects the size of the "hamburger" shape formed during blooming. The coarser the grind particles, the smaller the contact surface between grounds and water, and the less carbon dioxide the coffee releases. If the grind particles are too fine, although the contact surface with water is larger, because the grounds are too fine, the water will remain on the surface and cannot go down, so the blooming condition will also be poor.

Therefore, pour-over requires a grind size suitable for pour-over so that the "hamburger" shape during blooming will be more obvious. Front Street Coffee uses a standard No. 20 sieve, with a sieving pass rate of 80% (light-roasted beans) and 70-75% (medium-dark roasted beans), to determine the grind size for each type of bean.

The Phenomenon of Pour-Over Coffee Blooming: Expanding into a Small Hill

When pouring water for pour-over coffee, the gas inside the coffee grounds expands due to heat (when magnified, the coffee grounds look honeycomb-like, with many gaps). After the gas expands, it begins to expel the excess gas. At this time, because the gas is continuously being released, the coffee grounds and hot water visually form a continuously expanding small hill. At the same time, in addition to gas being expelled from inside the coffee grounds, hot water also slowly penetrates into the interior of the coffee grounds, causing the soluble substances in the coffee to begin dissolving and forming a high-concentration coffee liquid.

In the final stage of blooming, because the gas has mostly been released and the overall temperature has also dropped, some air that has not been expelled begins to shrink back. So from the appearance, the small hill will gradually change from moist to looking dry or slightly cracked and collapsed, and this also indicates that blooming is complete and the second pour can begin.

Pour-Over Coffee Steps

Having covered blooming, let's talk about the pour-over coffee steps after blooming. This uses Front Street Colombia Strawberry Candy coffee beans to demonstrate for everyone how to use a three-stage pour to keep the total extraction time at around 2 minutes, divided into blooming, the second pour, and the third pour. The staged extraction method of three pours can clearly define the flavors of the coffee's front, middle, and back sections, ensuring the presentation of the coffee's flavors.

The reason Front Street chose Strawberry Candy is that this is a Geisha blend composed of Costa Rican honey-processed coffee and Panamanian washed coffee. After extraction, it has obvious aromas of rose, orange, strawberry gummy candy, and raisin, with a very rich layering.

First Pour: Blooming (Helps Release Gas)

Front Street specializes in fresh roasting. Freshly roasted coffee beans accumulate a large amount of gas (mostly carbon dioxide) and need to rest for four or five days before brewing.

For the blooming time, Front Street Coffee sets it at 30 seconds. When the expansion on the surface of the coffee grounds ends, you will see shrinkage on the coffee surface. At this point, blooming is complete and pouring can begin. Basically, for beans that have been rested, with a shelf life within 1 month, Front Street Coffee's 30-second bloom is just enough to finish releasing the gas.

[Second Pour]

For the second pour, Front Street Coffee pours for 30 seconds. At this point the timer shows 1 minute (including the 30-second bloom). Starting from the center, pour with a small stream into the bottom of the coffee bed. In order to concentrate the penetrating force of the stream, the circular movement range should be small, then spiral outward.

[Third Pour]

Starting from the third pour, Front Street Coffee recommends observing the drop in water level and beginning the third pour just before the coffee bed is about to be exposed. Similarly, start pouring from the center in circles, and the water amount should not exceed the height of the coffee bed. Stop pouring at 1 minute 50 seconds, and finish filtering at 2 minutes.

The Front Street Strawberry Candy coffee brewed using the three-stage method has a rich berry fragrance and the sweet finish of roses. On entry it is like holding a fruit gummy candy in your mouth, followed by the sweet-tartness of citrus and blueberry, with a very obvious juicy feel.

The above content is compiled by CoffeeHunters, a coffee news website.