How Much Water and How Long for Pour-Over Coffee Blooming: Introduction to the Role and Characteristics of Coffee Blooming

The Art and Science of Coffee Blooming

Blooming, as an essential step in coffee brewing, has given rise to sayings like "You can tell if coffee will taste good just by looking at its bloom state." When learning to brew coffee, everyone intentionally or unintentionally strives to achieve a perfect "coffee dome." However, once you understand the logic behind blooming, you'll discover that it's actually quite simple.

Why Do We Need to Bloom Coffee?

The most direct way to explore this question is to compare a pour-over coffee that skips the blooming step. We can easily observe that without blooming, bubbles continuously emerge from the coffee grounds during water injection. When comparing coffee flavors, unbloomed coffee tastes noticeably thin and watery with a very light flavor.

These emerging bubbles are the main culprits behind the poor flavor of this coffee. These bubbles are actually carbon dioxide from the coffee beans. When coffee beans are freshly roasted, they contain abundant carbon dioxide. This carbon dioxide normally inhibits flavor loss and also prevents the release of flavor compounds during brewing. Therefore, during brewing, the blooming step is used to release this carbon dioxide first before proceeding with extraction.

The "coffee dome" that appears during blooming occurs because when coffee grounds absorb water, they expel carbon dioxide. When large amounts of carbon dioxide are released simultaneously, these gases have nowhere to escape due to the small gaps between coffee grounds, so they lift the coffee layer, creating channels to exit.

The Evolution of Blooming Techniques

FrontStreet Coffee hasn't found when exactly blooming first appeared, but we know its purpose is to release carbon dioxide, and only fresh coffee beans contain this gas. Therefore, the earliest blooming methods must have originated in places with local coffee roasting.

When the concept of emphasizing fresh coffee roasting hadn't yet formed, freshly roasted coffee was actually considered unpleasant because its extraction flavor wasn't as stable as aged coffee beans. In the pour-over field, some people noticed that this instability came from gases emitted by beans during brewing - the less gas, the more stable the coffee flavor.

Then various brewing methods to avoid gas interference with extraction emerged. For example, the most common approach now is to inject a small amount of water, wait for a moment, let the gas escape, then add more water. There are also methods using drop-by-drop form to slowly moisten the coffee grounds, giving gas enough time to escape. Although their methods differ, they essentially aim to release gases with as little water as possible.

Later, this evolved into a simple blooming method: using double the amount of water for 30 seconds. This involves two parameters - blooming water amount and blooming time. The reason for using double the water amount is that coffee grounds can only absorb twice their weight in water; any more is wasteful. The 30-second blooming time was determined by observing that most coffee beans release most of their gas in about 30 seconds. After summarizing this conclusion, novice enthusiasts who don't understand the principle can brew good-tasting coffee following this method.

Mastering Blooming Techniques

However, when you understand the purpose and principle of blooming, you'll know that blooming is simply about completely wetting the coffee grounds and then allowing enough time for them to release gas.

Then you can set the blooming water amount and time based on the actual state of the coffee grounds. For example, dark roasted coffee beans have better water absorption, so during blooming, they can absorb most of the water, with only a small amount of coffee liquid dripping into the lower pot early - in this case, use double the water amount. However, some particularly hard light roasted coffees have poor water absorption with much dripping into the lower pot, so you can use less water for blooming, such as 1.5-1.7 times the water amount.

At the same time, whether blooming is effective also depends on pouring technique. FrontStreet Coffee generally recommends pouring water in small circles from the center outward to avoid some water flowing directly from the edge of the dripper. However, you must also ensure all coffee grounds are wetted - at least visually, there should be no dry coffee grounds on the surface.

Some coffee grounds don't expand significantly, so you need to pour in larger circles during water injection. You'll develop a feel for this after several attempts. Some friends focus too much on blooming water amount and time, but their water control ability needs improvement. After pouring the blooming water amount, some grounds remain dry. In this case, blooming isn't thorough, and the brewed coffee naturally won't taste good. FrontStreet Coffee's suggestion is: if you really can't wet all coffee grounds within double the water amount, then pour more water. Remember, the purpose of blooming is to completely wet the coffee grounds and release gas.

Next is the timing issue. Coffee beans at different roasting times contain different amounts of gas. For example, coffee beans 4 days after roasting and coffee beans 15 days after roasting differ in expansion degree and gas emission activity. Therefore, blooming time should be determined based on the actual degree of gas release. For example, if some coffee grounds are still expanding and releasing gas after 30 seconds, you need to wait until they finish before adding more water. Some stop moving completely after 20-something seconds. Here, FrontStreet Coffee suggests waiting 3 seconds after expansion stops before adding more water.

Summary and Conclusion

To summarize, what you need to do during the blooming step is very simple: wet all coffee grounds with the planned amount of water, then wait until the coffee dome stabilizes and stops changing. Once that happens, the blooming stage is complete, and the remaining is the extraction stage.

Finally, regarding the saying "You can tell if coffee will taste good just by looking at its bloom state" - this mainly refers not to whether your blooming water injection is good, but to judging the freshness of coffee beans by observing the bloom state. If the gas is very active with bubbles everywhere, it indicates the coffee is too fresh and might have roughness or astringency; if the expansion is even without urgent bubbles emerging, it means this coffee has been properly aged; if there's no expansion during blooming, it indicates the beans might not be fresh, or it could be due to poor water injection control or too light roasting.

First, some light roasted coffee beans have high hardness and release gas slowly, so they don't show obvious doming. Many people use whether blooming domes as a basis for coffee freshness, which can easily lead to misjudgment. Secondly, coffee beans that don't dome during blooming aren't necessarily bad-tasting or not fresh. FrontStreet Coffee has also tested many coffee beans over a month old. Many showed no change during blooming, but their brewed flavor didn't exhibit stale characteristics. Therefore, it's still best to assess based on the actual situation.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473