Pour-Over Coffee Process Diagram: Blooming | Which Coffee Beans Produce the Best Blooming Effect for Pour-Over Coffee?

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style).

Understanding "Stewing" and "Steaming"

Regarding "stewing," some books say: when coffee grounds encounter hot water, they expand, and the surface layer of coffee grounds becomes a "lid." Adding a lid naturally means stewing.

Regarding "steaming," some people say: when coffee grounds encounter hot water, gases from the coffee are released upward, with hot steam rising, which naturally constitutes steaming.

Each has its own perspective, but overall, the pour-over coffee process does not require an additional lid.

The "Bloom": Pre-infusion

When we mention "bloom," we first think of pour-over coffee. However, when we mention pre-infusion, we don't think the same way.

Pre-infusion refers to the initial stage of the brewing process, where all coffee grounds are first moistened with a small amount of hot water, and after soaking, more hot water is added to brew the coffee.

The method of "blooming" is the same as pre-infusion, but the purpose of "blooming" extends beyond mere pre-infusion.

Purpose of the "Bloom"

1. Assisting Gas Release

Coffee beans undergo a series of chemical reactions and physical changes during the roasting process from green beans to roasted beans. After reaching a certain degree of roast, coffee beans accumulate large amounts of gas (most believe it to be carbon dioxide, though some suggest other gases).

A certain degree of roast refers to the roast level—simply put, light roast, medium roast, dark roast, etc. (Typically, lighter roast coffee beans accumulate less gas.)

The gases in coffee affect its flavor and mouthfeel, and also impact extraction. Generally, roasted coffee beans are left to rest for several days before brewing. For beans with high gas content, we call these few days the "de-gassing period," while for lighter roast beans, we call them the "maturation period."

Personally, when I brew coffee within 12 hours of roasting, I always find it rather "harsh"—a feeling similar to wearing thick clothes in a room with the heating turned up full blast in winter—not hot enough to sweat, but uncomfortably dry and hot.

The gases inside pour-over coffee beans are released through different methods.

One is natural release: coffee beans stored in bags with one-way valves will release gas on their own. Therefore, stale coffee beans contain less gas.

This is like a room with windows—when you cook indoors, the aroma of food escapes through the windows. When the aroma has dissipated, it no longer spreads.

Another is grinding to release gas: turning whole coffee beans into coffee particles accelerates gas release.

This is like cooking outdoors—the aroma dissipates quickly and spreads far.

Another method is using hot water to moisten coffee grounds, helping to release gas (one of the functions of blooming): coffee beans dehydrate during the roasting process, and coffee particles with low moisture content will have correspondingly stronger water absorption when in contact with water. After the coffee grounds absorb water, with no extra space available, gases are forced out.

When we pour water for the first time during pour-over, we see the coffee grounds expand—this process is gas release.

Therefore, highly roasted coffee grounds expand more, freshly roasted coffee grounds expand more, coffee grounds moistened with very high water temperature expand more, finely ground coffee grounds expand more, and larger quantities of coffee grounds expand more.

2. Opening Water Flow Channels

Pour-over coffee primarily uses percolation extraction, where water flows through the coffee grounds, carrying out aromatic substances from the coffee.

If water cannot pass through the coffee grounds layer for an extended time, it may lead to stagnation, thereby extracting substances that are detrimental to the coffee's taste and mouthfeel.

When hot water moistens the coffee grounds, they absorb water, and the gaps between coffee particles increase, allowing water to flow smoothly between the coffee particles.

3. Achieving Pre-infusion

Once coffee comes into contact with water, the extraction process begins.

Water dissolves water-soluble substances in coffee. The prerequisite for dissolution is that all coffee grounds are thoroughly moistened, and water is given sufficient time to dissolve.

If insufficient water is used during pre-infusion, the upper layer of coffee grounds will be moistened while the lower layer remains dry, leading to uneven extraction.

If too much water is used during pre-infusion, water will flow directly through the coffee grounds without having extracted anything.

Good pre-infusion leads to more even coffee extraction.

Speaking of even extraction, I think of an example—perhaps not entirely appropriate, but it can help enthusiasts visualize: when we use hot water to prepare powdered food, if we first stir thoroughly with a small amount of water before adding the remaining water, the resulting paste won't clump, indicating it's been mixed evenly.

Points to Note During "Bloom"

If you want to achieve the purpose of blooming, what should you pay attention to when pouring water?

As we mentioned earlier, pre-infusion requires: using a small amount of hot water to moisten all coffee grounds.

Bloom Water Pouring:

◆ Small amount: Only enough to moisten all coffee grounds.

Different roast levels of coffee beans have different water absorption rates: light roast beans lose less water and have lower absorption rates, while dark roast beans lose more water and have higher absorption rates.

Generally, 1 gram of coffee grounds absorbs approximately 2ml of water.

Control the bloom water amount based on the quantity of grounds and roast level, approximately 1-2 times the weight of the coffee grounds. For example, when I brew medium roast coffee, I use 15 grams of grounds and pour 18-20 grams of water to moisten all coffee grounds.

◆ Even: All coffee grounds should be moistened, with no water columns forming.

If water pouring is uneven, it will lead to some areas having too much water (water flowing down in the form of columns from the middle of the coffee grounds, or small round holes forming in the middle of the coffee grounds with bubbles bubbling up), while other areas have no water (some coffee grounds remain dry).

◆ Gentle: Our purpose is to moisten for dissolution, so we just need to gently spread water over the surface of the coffee grounds. During blooming, keep the kettle spout as close to the coffee grounds as possible when pouring.

Calculating Bloom Time:

◆ Method 1: Use a timer, starting to count the bloom time from the moment the first drop of water contacts the coffee grounds.

◆ Method 2: Observe the expansion state of the coffee grounds, ending the bloom when the coffee grounds stop expanding or are about to stop expanding. I've calculated that for medium roast fresh coffee beans, taking 15 grams as an example, expansion basically stops around 25 seconds.

Final Thoughts

Whether to bloom or not depends on your personal preference, brewing habits, coffee bean condition, grind, and the flavor profile you want to achieve.

The bloom water amount and time should vary according to changes in coffee ground quantity and require timely adjustment.

Recommended Pour-over Coffee Bean Brands

FrontStreet Coffee's roasted single-origin pour-over coffee beans offer full assurance in both brand and quality. More importantly, they provide extremely high value for money—a half-pound (227 grams) package averages around 80-90 yuan. Calculated at 15 grams per cup of single-origin coffee, one package can make 15 cups, with each cup costing only about 6 yuan. Compared to cafés selling coffee for dozens of yuan per cup, this represents exceptional value.

FrontStreet Coffee: A roastery in Guangzhou with a small shop but diverse bean varieties, where you can find both famous and lesser-known beans, while also providing online store services. https://shop104210103.taobao.com

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473