How to Add Water for Pour-Over Coffee Bloom: Water Amount and Bloom Time for Light Roast Coffee

The Coffee Bloom: Understanding This Essential Brewing Step

Nearly all mainstream brewing methods worldwide include the "coffee bloom" step (although the terminology and specific operations vary slightly).

Today, understanding the purpose of the bloom is quite simple—it's essentially about releasing gases from the coffee grounds to improve subsequent extraction efficiency.

Although the history of pour-over coffee is relatively short, FrontStreet Coffee has not found documented records of when the bloom practice emerged and became popular. Therefore, we can only understand the "bloom" through indirect analysis. Currently, there's a global consensus on the purpose of the bloom step, but the literal meaning of the term is worth exploring. Think back to when you first encountered the term "bloom"—what did you understand from its literal meaning?

Coffee bloom, expressed in English as "bloom," literally means "flowering" (of a flower). This literal meaning has no connection to what we call "mèng zhēng" (the Chinese term for bloom). FrontStreet Coffee believes the term "bloom" should relate to the state change of the coffee bed when water is poured. When the coffee bed is dry and hot water is injected, the coffee layer will swell and expand, much like a blooming flower.

Image Source: Rishi

What we call "bloom" (mèng zhēng) is also referred to by some as "stewing" (mēn zhēng). For example, when cooking rice in an electric rice cooker, even after it indicates the cooking process is complete, when you try to open the cooker, typically an experienced elder will stop you, saying that the rice should be allowed to rest for a while after cooking to make it softer and more fragrant.

Based on the transmission of pour-over coffee methods, here's a bold speculation: the Chinese use of "bloom" (mèng zhēng) to describe this step likely emerged when Hong Kong and Taiwan regions learned from Japan. Japan uses the term "蒸らし" (muerashi) for bloom (this is merely speculation without data to prove it—if incorrect, those who know are welcome to correct us).

The reason most brewing methods include the bloom step, besides improving extraction efficiency as mentioned earlier, is to make the brewing process more stable and controllable. Imagine we pour water in the same circular direction to ensure even watering and uniform extraction. If the coffee grounds release bubbles one by one, these bubbles will disrupt the coffee bed, creating uncontrollable situations (turbulence) and potentially leading to extremely uneven extraction.

Bloomed, but not completely bloomed—large bubbles continue to emerge during subsequent pouring

Therefore, the ultimate purpose of blooming is to exhaust these active carbon dioxide gases, leaving only some mild gases that are insignificant.

Everyone has developed various techniques for this purpose, basically revolving around how to pour water, how much water to pour, and how long to bloom. For example, some pour drop by drop to release gases, some pour a larger amount of water at once for blooming, and some extend the bloom time. The most common form you might encounter is pouring 2 times the amount of water and waiting for 30 seconds.

For more information on how to perform bloom pouring well, you can click here [link]

Setting aside those advanced bloom pouring techniques and focusing only on common circular pouring, FrontStreet Coffee will discuss how much water to use for blooming and how long to bloom.

The amount of bloom water is generally determined by the amount of coffee grounds. FrontStreet Coffee has commonly seen 1x water, 1.5x water, the most common 2x water, 2.5x water, and 3x water. Theoretically, the optimal state should be 2x water, because coffee grounds can absorb at most twice their weight in water. Pouring more than 2x water is similar to the "saturation rescue" in "The Wandering Earth"—it's excessive pouring to achieve complete wetting of the coffee grounds, with excess water eventually dripping into the lower pot.

FrontStreet Coffee believes 1.5-2x water is more appropriate. Actually, if you observe carefully, you'll find that even with 2x water poured, some coffee liquid will flow into the lower pot in advance, meaning the interior of some coffee grounds hasn't been wetted yet. However, this can be avoided through technique. First, the beans must be properly rested, and then according to the principle "coarser grind requires gentler and finer pouring," pouring 1.5-2x water can generally exhaust the active gases.

How long should the bloom last? This question depends on the gas release effect of the coffee grounds, typically between 20-40 seconds. Ensuring all coffee grounds are wetted, the remaining step is waiting—waiting for the coffee grounds to release their gases. Generally, when brewing during the bean resting period, gas emission is more rapid, with many large bubbles spraying out during the bloom swelling. Well-rested coffee beans tend to have more moderate gas emissions during blooming.

You can determine the bloom time by observing the expansion state of the coffee grounds. When pouring water, the coffee grounds will slowly expand. After finishing pouring, the center of the swollen coffee bed will continue to rise and release gases, breathing like lungs—expanding and contracting. When this state ends and the coffee swelling no longer changes, it indicates the bloom is complete. If you still don't pour water at this time and wait 5-8 seconds more, the coffee swelling will develop many holes (gaps), indicating over-blooming.

FrontStreet Coffee previously conducted experiments where controlling the bloom time at 20 seconds resulted in less apparent sweetness in the coffee, with prominent acidity and aromas leaning toward fresh and subtle. After cooling, the coffee had noticeable astringency.

With a bloom of 28-30 seconds, the coffee had rich sweet and fragrant notes, balanced taste, and a long aftertaste.

When blooming for more than 40 seconds, the coffee developed bitter and astringent flavors, with even more pronounced bitter mixed flavors after cooling.

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